Oxygen

Name Reactions

Recent Literature

The use of tert-butyl nitrite as the co-catalyst in a 2-azaadamantane-N-oxyl (AZADO)- and 9-azanoradamantane-N-oxyl (nor-AZADO)-catalyzed efficient aerobic oxidation of primary alcohols in MeCN instead of the previously reported AcOH provides the corresponding aldehydes selectively. The addition of saturated aqueous NaHCO₃ after the completion of the reaction suppresses the overoxidation of the product during the workup.
M. Shibuya, K. Furukawa, Y. Yamamoto, Synlett, 2017, 28, 1554-1557.

Cu/TEMPO catalyst systems show reduced reactivity in aerobic oxidation of aliphatic and secondary alcohols. A catalyst system consisting of (^MeObpy)CuOTf and ABNO mediates aerobic oxidation of primary, secondary allylic, benzylic, and aliphatic alcohols with nearly equal efficiency. The catalyst exhibits broad functional group compatibility, and most reactions are complete within 1 h at room temperature using ambient air as oxidant.
J. E. Steves, S. S. Stahl, J. Am. Chem. Soc., 2013, 135, 15742-15745.

8-Azabicyclo[3.2.1]octan-8-ol (ABOOL) and 7-azabicyclo[2.2.1]heptan-7-ol (ABHOL) feature small bicyclic backbones and are known to be stable. These hydroxylamines can efficiently catalyze the oxidation of various secondary alcohols to their corresponding ketones using molecular oxygen in ambient air as the terminal oxidant and copper cocatalysts at room temperature.
M. Toda, Y. Sasano, M. Takahashi, S. Fujiki, K. Kasabata, T. Ono, K. Sato, Y. Kashiwagi, Y. Iwabuchi, J. Org. Chem., 2023, 88, 1434-1444.

A (bpy)CuI/TEMPO catalyst system enables an efficient and selective aerobic oxidation of a broad range of primary alcohols, including allylic, benzylic, and aliphatic derivatives, to the corresponding aldehydes using readily available reagents, at room temperature with ambient air as the oxidant. The catalyst system is compatible with a wide range of functional groups and shows a high selectivity for 1° alcohols.
J. M. Hoover, S. S. Stahl, J. Am. Chem. Soc., 2011, 133, 16901-16910.

The combination of Fe(NO₃)₃·9H₂O and 9-azabicyclo[3.3.1]nonan-N-oxyl enables an efficient aerobic oxidation of a broad range of primary and secondary alcohols to the corresponding aldehydes and ketones at room temperature with ambient air as the oxidant.
L. Wang, S. Shang, G. Li, L. Ren, Y. Lv, S. Gao, J. Org. Chem., 2016, 81, 2189-2193.

Imidazolium salts bearing TEMPO groups generate in situ Cu-NHC-TEMPO complexes with commercially available copper powder. These easily available Cu-NHC-TEMPO complexes are quite efficient catalysts for selective, aerobic oxidation of primary alcohols into aldehydes in excellent yields.
X. Liu, Q. Xia, Y. Zhang, C. Chen, W. Chen, J. Org. Chem., 2013, 78, 8531-8536.

The combination of TEMPO and CAN can be used for the aerobic oxidation of benzylic and allylic alcohols into their corresponding carbonyl compounds. However, steric hindrance has been observed to impede the reaction with some substituted allylic systems. The present method is superior to others currently available due to its relatively short reaction times and excellent yields.
S. S. Kim, H. C. Jung, Synthesis, 2003, 2135-2137.

The combination of N-hydroxyphthalimide (NHPI), a Co species, and optionally a small amount of a (per)benzoic acid catalyzes highly efficient oxidations of alcohols with oxygen. Primary alcohols are rapidly oxidized to the corresponding carboxylic acids, terminal vic-diols give one carbon less carboxylic acids, while internal vic-diols were selectively oxidized to 1,2-diketones.
T. Iwahama, Y. Yoshino, T. Keitoku, S. Sakaguchi, Y. Ishii, J. Org. Chem., 2000, 65, 6502-6507.

A convenient method enables the preparation of a silica gel supported TEMPO catalyst. The catalyst prepared from [4-hydroxy-TEMPO + NaCl]/SiO₂ was used for an aerobic oxidation of alcohols to carbonyls under mild reaction conditions in the presence of Fe(NO₃)₃ • 9 H₂O. Alcohols were converted to the corresponding carbonyls in good to excellent yields. After a simple filtration, the catalyst can be reused at least six times.
N. Tamura, T. Aoyama, T. Takido, M. Kodomari, Synlett, 2012, 23, 1397-1407.

TEMPO-derived reagents tagged with multiple perfluoroalkyl chains and triazole moieties promote the oxidation of alcohols to aldehydes in organic solvent/water mixtures with reaction rates comparable to homogeneous TEMPO reagents, but can be easily recovered by liquid/emulsion filtration.
A. Gheorghe, T. Chinnusamy, E. Cuevas-Yañez, P. Hilgers, O. Reiser, Org. Lett., 2008, 10, 4171-4174.

The use of low loadings of a silver NHC catalysts enables a mild, selective oxidation of alcohols to aldehydes or carboxylic acids in the presence of BnMe₃NOH or KOH under dry air in excellent yield. The catalytic system can also be used for a one-pot synthesis of imines in excellent yield.
L. Han, P. Xing, B. Jiang, Org. Lett., 2014, 16, 3428-3431.

A robust and effective Pd catalyst for the aerobic oxidation of various alcohols has been discovered. Using a slightly higher concentration of acetic acid as additive and extending the reaction times, the oxidation can be carried out under ambient atmosphere of air.
D. R. Jensen, M. J. Schultz, J. A. Mueller, M. S. Sigman, Angew. Chem. Int. Ed., 2003, 42, 3810-3813.

A heterogeneous palladium(II) acetate-pyridine complex supported by hydrotalcite catalyzes the aerobic oxidation of a variety of primary and secondary alcohols into the corresponding aldehydes and ketones in high yields using atmospheric pressure of air as a sole oxidant under mild conditions in toluene.
N. Kakiuchi, Y. Maeda, T. Nishimura, S. Uemura, J. Org. Chem., 2001, 66, 6620-6625.

Pd/C in aqueous alcohol with molecular oxygen, sodium borohydride, and potassium carbonate efficiently oxidized benzylic and allylic alcohols. Sodium borohydride allows a remarkable reactivation of active sites of the Pd surface.
G. An, M. Lim, K.-S. Chun, H. Rhee, Synlett, 2007, 95-98.

A new, highly recoverable palladium-based catalyst for the aerobic oxidation of alcohols combines an organic ligand and mesoporous channels that led to enhanced activity, prevention of agglomeration and the generation of a durable catalyst.
B. Karimi, S. Abedi, J. H. Clark, V. Budarin, Angew. Chem. Int. Ed., 2006, 45, 4776-4779.

The use of an ortho-naphthoquinone catalyst enables a biomimetic alcohol dehydrogenase (ADH)-like oxidation protocol as green alternative to existing stoichiometric and metal-catalyzed alcohol oxidation reactions. The developed organocatalytic aerobic oxidation protocol proceeds through an intramolecular 1,5-hydrogen atom transfer of naphthalene alkoxide intermediates.
J. Baek, T. Si, H. Y. Kim, K. Oh, Org. Lett., 2022, 24, 4982-4986.

Copper N-heterocyclic carbene complexes serve as catalysts for both aerobic oxidation of alcohols to aldehydes and reduction of imines to amines. A one-pot tandem synthetic strategy affords useful secondary amines from benzylic alcohols and anilines via an oxidation-reduction strategy.
L.-W. Zhan, L. Han, P. Xing, B. Jiang, Org. Lett., 2015, 17, 5990-5993.

N-functionalized amino acids serve as powerful N,O-bidentate ligands in an aerobic copper/TEMPO-catalyzed system for the oxidation of benzylic alcohols in water. Under optimized reaction conditions, a broad range of primary and secondary benzylic alcohols have been efficiently converted into carbonyl compounds in very good yields.
G. Zhang, J. Lei, X. Han, Y. Luan, C. Ding, S. Shan, Synlett, 2015, 26, 779-784.

G. Zhang, J. Lei, X. Han, Y. Luan, C. Ding, S. Shan, Synlett, 2015, 26, 779-784.

A combination of FeCl₃, L-valine and TEMPO oxidizes a wide range of primary/secondary benzyl, allylic, and heterocyclic alcohols to aldehydes and ketones with good to excellent isolated yields in the presence of oxygen.
G. Zhang, S. Li, J. Lei, G. Zhang, X. Xie, C. Ding, R. Liu, Synlett, 2016, 27, 956-960.

Eosin Y catalyzes an efficient photochemical aerobic oxidation of various benzyl alcohols to the corresponding aldehydes or ketones in excellent yields under mild reaction conditions using O₂ as oxidant. The catalyst system offers good functional-group tolerance and exquisite chemoselectivity.
Z.-X. He, B. Yin, X.-H. Li, X.-L. Zhou, H.-N. Song, B.-B. Xu, F. Gao, J. Org. Chem., 2023, 88, 4765-4769.

Various imidazolium salts bearing hydrophilic groups afford water-soluble NHC copper complexes. These copper complexes catalyze a selective oxidation of benzyl alcohols to the corresponding aldehydes in water at room temperature without the need for a base.
C. Chen, B. Liu, W. Chen, Synthesis, 2013, 45, 3387-3391.

Optimized selective aerobic oxidations in ionic liquids convert various activated primary alcohols into their corresponding acids or aldehydes in good to excellent yields. The newly developed catalytic systems could also be recycled and reused for three runs without any significant loss of catalytic activity.
N. Jiang, A. J. Ragauskas, J. Org. Chem., 2007, 72, 7030-7033.

The reaction of KBrO₃ and NH₂OH • HCl in situ generates NO_x and Br anion, which allows in the presence of 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO) an activation of dioxygen to oxidize various benzylic alcohols quantitatively to their corresponding carbonyl compounds under mild conditions.
G. Yang, W. Wang, W. Zhu, C. An, X. Gao, M. Song, Synlett, 2010, 437-440.

The use of CsPbBr₃ perovskite as a heterogeneous photocatalyst enables a cost-effective and highly efficient oxidation of alcohols to afford aldehydes/ketones exclusively with an excellent yield at ambient temperature under an air atmosphere. Moreover, the photocatalyst can be recycled at least 5 times without a significant decrease in catalytic activity.
Q. Fan, D. Liu, Z. Xie, Z. Le, H. Zhu, H. Zhu, X. Song, J. Org. Chem., 2023, 88, 14559-14570.

The use of visible-light-induced silver catalysis enables a controlled singlet-oxygen-mediated selective C-S bond cleavage reaction of benzyl thiols to afford carbonyl compounds.
B. Hong, K. C. C. Aganda, A. Lee, Org. Lett., 2020, 22, 4395–4399.

Autoxidative sp³ C-H transformation of diarylmethanes in the presence of oxygen mediated by t-BuONa provides diaryl ketones in very good yields under mild reaction conditions, without transition metal catalysts or additional chemical oxidants.
J.-S. Li, F. Yang, Q. Yang, Z.-W. Li, Z.-Q. Chen, Y.-D. Da, P.-M. Huang, C. Chen, Y. Zhang, L-Z. Huang, Synlett, 2017, 28, 994-998.

Visible-light-induced photocatalysis enables a highly efficient decarboxylative oxidation of carboxylic acids with molecular oxygen as a green oxidant and copper as a co-catalyst. This reaction worked smoothly on various type of acids, and could potentially be used in modifications of natural products.
M. K. Zaman, S. N. Khan, Y. Cai, Z. Sun, Synlett, 2023, 34, 2029-2033.

Catalyzed by Se/Fe via hybrid mechanisms, the carbon-carbon double bond in alkenes can break to produce carbonyls under mild conditions. Since O₂ can be used as a partial oxidant, the employed H₂O₂ amount can be lowered to avoid peroxide residues, making the process even safer for operation.
X. Li, H. Hua, Y. Liu, L. Yu, Org. Lett., 2023, 25, 6720-6724.

The combination of 1,2-dibutoxyethane/O₂ enables an effective and green oxidative cleavage of olefins to carboxylic acids in very good yields. This oxidation system offers excellent functional-group tolerance, is applicable for large-scale synthesis, and works without an external initiator, catalyst, or additive.
J. Ou, H. Tan, S. He, W. Wang, B. Hu, G. Yu, K. Liu, J. Org. Chem., 2021, 86, 14974-14982.

Photoirradiation of toluene derivatives with two equivalents of bromine in benzotrifluoride-water provides benzoic acid derivatives in good yields using either a fluorescent lamp, blue LEDs (454 nm), or UV LEDs (385 nm). The reaction might proceed through dibromination of benzylic carbon, generation of the benzylic radical via oxidative C-H abstraction, formation of benzoyl bromide, and hydrolysis.
M. Kirihara, Y. Sakamoto, S. Yamahara, A. Kitajima, N. Kugisaki, Y. Kimura, Synlett, 2022, 33, 1670-1674.

A one-step reaction of trisubstituted olefins provides enones in good yields with high regioselectivity under visible-light irradiation in the presence of molecular oxygen and a photocatalyst. The reaction tolerates oxygen- and nitrogen-containing functional groups, heteroaromatic rings, and cyclopropanes.
S. Harada, D. Matsuda, T. Morikawa, A. Nishida, Synlett, 2020, 31, 1372-1377.

A copper-catalyzed aerobic C-C cleavage of single bonds enables a transformation of epoxides into ketones.
L. Gu, C. Jin, H. Zhang, L. Zhang, J. Org. Chem., 2014, 79, 8453-8456.

An aerobic photoepoxidation of α,β-unsaturated ketones is driven by visible light in the presence of tetramethylguanidine (TMG), tetraphenylporphine (H₂TPP), and molecular oxygen under mild conditions to provide α,β-epoxy ketones in good yields in 96 h. The reaction time can be shortened to 5 h using flow synthesis.
Y. Wu, G. Zhou, Q. Meng, X. Tang, G. Liu, H. Yin, J. Zhao, F. Yang, Z. Yu, Y. Luo, J. Org. Chem., 2018, 83, 13051-13062.

Upon addition of B(C₆F₅)₃·H₂O, the oxidation potential of quinoxalinone increased remarkably, enabling the photoredox aerobic oxidation of alcohols, thiols, and alkenes toward carbonyl compounds and dithioethers under visible light conditions. This combination could serve as a versatile photocatalyst system for both energy transfer and single electron transfer processes.
J. Huang, Y.-X. Luo, L. Wang, X.-Y. Tang, Org. Lett., 2023, 25, 5613-5618.

A light-driven, Mn-catalyzed protocol for the selective oxidation of alkenes to carbonyls under 1 atm of O₂ provides ketones and aldehydes under clean, mild conditions. Aromatic as well as various nonactivated aliphatic alkenes could be oxidized with a first row, biorelevant metal catalyst. Moreover, the protocol shows a very good functional group tolerance.
Z. Huang, R. Guan, M. Shanmugam, E. L. Bennett, C. M. Robertson, A. Brookfield, E. J. L. MeInnes, J. Xiao, J. Am. Chem. Soc., 2021, 143, 10005-10013.

CsPbBr₃ nanocrystals catalyze a facile visible-light-driven oxidative cleavage of C=C bonds to the corresponding carbonyls. This catalytic system was applicable to a wide range of terminal and internal alkenes.
Q. Fan, H. Zhang, D. Liu, C. Yan, H. Zhu, Z. Xie, Z. Le, J. Org. Chem., 2023, 88, 7391-7400.

Sodium benzene sulfinate catalyzed a visible-light-driven aerobic oxidative cleavage of olefins to provide the corresponding aldehydes and ketones under transition-metal-free conditions. Notably, α-halo-substituted styrenes proceeded with photoinduced oxidation to finally afford α-halo-acetophenones with halogen migration.
Y.-X. Chen, J.-T. He, M.-C. Wu, Z.-L. Liu, K. Tang, P.-J. Xia, K. Chen, H.-Y. Xiang, X.-Q. Chen, H. Yang, Org. Lett., 2022, 24, 3920-3925.

A mild and operationally simple protocol for the selective aerobic oxidation of aromatic olefins to carbonyl compounds is catalyzed by a Fe(III) species bearing a pyridine bisimidazoline ligand at 1 atm of O₂. The method cleaves α- and β-substituted styrenes to afford benzaldehydes and aromatic ketones in high yields with excellent chemoselectivity and very good functional group tolerance.
A. Gonzalez-de-Castro, J. Xiao, J. Am. Chem. Soc., 2015, 137, 8206-8218.

In a 2,2-azobis(isobutyronitrile)-catalyzed oxidative cleavage of gem-disubstituted alkenes with molecular oxygen as the oxidant, carbonyl compounds were obtained as the desired products in high yield under mild conditions.
G.-Z. Wang, X.-L. Li, J.-J. Dai, H.-J. Xu, J. Org. Chem., 2014, 79, 7220-7225.

An iron-sulfur complex formed by the simple mixture of FeCl₃ with S₃^•- generated in situ from K₂S mediates an aerobic oxidation of terminal alkenes under an atmosphere of O₂ (balloon). The reaction could proceed on a gram scale, expanding the application of S₃^•- in organic synthesis.
J.-J. Ai, B.-B. Liu, J. Li, F. Wang, C.-M. Huang, W. Rao, S.-Y. Wang, Org. Lett., 2021, 23, 4705-4709.

The use of bis(pinacolato)diboron enables a palladium-catalyzed alkene diacetoxylation with oxygen as both the sole oxidant and oxygen source. This method displayes good functional group tolerance with good yields and can be applied to late-stage modifications of natural products.
J. Huang, L. Ouyang, J. Li, J. Zheng, W. Yan, W. Wu, H. Jiang, Org. Lett., 2018, 20, 5090-5093.

Oxidation from alcohols to carboxylic acids are often conducted using at least a stoichiometric amount of an expensive and toxic oxidant. An efficient and practical sustainable oxidation technology of alcohols using pure O₂ or even air as the oxidant in the presence of a catalytic amount each of Fe(NO₃)₃·9H₂O/TEMPO/MCl provides a series of carboxylic acids in high yields at room temperature.
X. Jiang, J. Zhang, S. Ma, J. Am. Chem. Soc., 2016, 138, 8344-8347.

An N-heterocyclic carbene (NHC) organocatalytic aerobic oxidation of aldehydes provides the corresponding carboxylic acids under mild reaction conditions. Remarkably, this method enables an efficient conversion of different classes of aldehydes including highly challenging electron-rich aryl aldehydes, ortho-substituted aryl aldehydes, various heteroaromatic aldehydes and α,β-unsaturated aldehydes.
A. K. Khatana, V. Singh, M. K. Gupta, B. Tiwari, Synthesis, 2018, 50, 4290-4294.

An aerobic oxidation of a wide range of aldehydes to carboxylic acids in both organic solvent and water under mild conditions is catalyzed by 5 mol % N-hydroxyphthalimide (NHPI) as the organocatalyst in the presence of oxygen as the sole oxidant. No transition metals or hazardous oxidants or cocatalysts were involved.
P.-F. Dai, J.-P. Qu, Y.-B. Kang, Org. Lett., 2019, 21, 1393-1396.

The use of potassium persulfate enables an aerobic oxidation of benzyl substrates to provide aryl carbonyl compounds including acetophenones, benzophenones, imides, and benzoic acids under mild conditions in the presence of pyridine. Neither transition metals nor halogens are required as additives.
Y. Hu, L. Zhou, W. Lu, Synthesis, 2017, 49, 4007-4016.

The use of CBr₄ as initiator enables a mild and metal-free aerobic oxidation of substituted toluenes to carboxylic acids under irradiation from a 400 nm blue light-emitting diode.
K. Zheng, X. Yan, G. Zhang, X. Yan, X. Li, X. Xu, Synlett, 2020, 31, 272-274.

A photocatalytic decarboxylation of α,β-unsaturated acids followed by a C-O cross-coupled esterification provides α-oxycarbonyl-β-ketones. Water as the source of oxygen for the ketone segment and aerial oxygen as an oxidant make the present dual Ir/Pd-catalytic methodology green and sustainable.
S. Mondal, S. Mondal, S. P. Midya, S. Das, S. Mondal, P. Ghosh, Org. Lett., 2023, 25, 184-189.

The combination of electrochemical synthesis and aerobic oxidation enables a transition-metal-free dioxygenation of alkenes to provide α-oxygenated ketones in an eco-friendly fashion. A wide range of alkenes and N-hydroxyimides provided α-oxygenated ketones in good yields.
C. Dai, Y. Shen, Y. Wei, P. Liu, P. Sun, J. Org. Chem., 2021, 86, 13711-13719.

An I₂-catalyzed oxidative cross-coupling of α-amino ketones with a wide range of alcohols provides α-carbonyl N,O-acetals with high functional group tolerance. Using a combination of air and dimethyl sulfoxide as oxidants, the protocol allows an efficient late-stage modification of biorelevant structures. Moreover, the use of other nucleophiles enables additional functionalization of α-amino ketones.
Y. Wang, M. Yang, C. Lao, H. Wang, Z. Jiang, J. Org. Chem., 2023, 88, 14470-14486.

An anthraquinone-catalyzed photooxidative keto-trifluoromethylation of styrenes with the readily available Langlois reagent (CF₃SO₂Na) under an oxygen atmosphere proceeds smoothly to give α-trifluoromethyl ketones in good yield with good selectivity.
E. Yamaguchi, Y. Kamito, K. Matsuo, J. Ishihara, A. Itoh, Synthesis, 2018, 50, 3161-3168.

In a Fe-catalyzed aerobic oxidative esterifications of arylacetonitriles, acyl electrophiles were in situ generated via chemoselective C(CO)-CN bond cleavage. Alcohols, alkoxsilanes, silicate esters, or borate esters can be acylated to the corresponding aryl esters in good to excellent yields under molecular oxygen. Dioxygen serves as both oxidant and reactant.
W. Kong, B. Li, X. Xu, Q. Song, J. Org. Chem., 2016, 81, 8436-8443.

The combination of potassium persulfate and ambient air enables a catalyst- and transition-metal-free oxidation of various internal alkynes to the corresponding 1,2-diketones in very good yields. Mechanistic studies indicate a radical process with both the persulfate salt and molecular oxygen as source of the incorporated oxygen atoms.
D. Shen, H. Wang, Y. Zheng, X. Zhu, P. Gong, B. Wang, J. You. Y. Zhao, M. Chao, J. Org. Chem., 2021, 86, 5354-5361.

An aerobic decomposition of 1,3-diaryl-2-diazo-1,3-diketones to 1,2-diaryl-1,2-diketones (benzils) can be catalyzed by a few dirhodium carboxylates (5 mol %) under a balloon pressure of oxygen at ambient temperatures. An oxygen atom from O₂ is shown to be incorporated into the product accompanied by the extrusion of a carbonyl unit from the starting materials.
J.-L. Zhu, Y.-T. Tsai, J. Org. Chem., 2021, 86, 813-828.

A conjugate addition of ethyl cyanoacetates to chalcones and subsequent iodine-promoted aerobic oxidation provides various α,δ-dicarbonyl esters. The present protocol features mild reaction conditions, high efficiency, easily available starting materials, and broad substrate scope.
H. Xu, M.-Y. Weng, H. Chen, Z. Zhang, Synthesis, 2020, 52, 1841-1846.

A mild and highly efficient photocatalytic oxidative radical addition reaction for the synthesis of unsymmetrical 1,4-dicarbonyl compounds utilizes a desulfurization process to generate electrophilic radicals, which add to α-halogenated alkenes and undergo further oxidation to deliver 1,4-dicarbonyl compounds.
Y. Dong, R. Li, J. Zhou, Z. Sun, Org. Lett., 2021, 23, 6387-6390.

The use of alkali metal hydrides as reagents enables a mild, efficient protocol for the aerobic oxidative cleavage of C-C bonds in aldehydes. The method is applicable to a broad substrate range.
S. A. Shipilovskikh, A. E. Rubtsov, A. V. Malkov, Org. Lett., 2017, 19, 6760-6762.

The use of MeCN:H₂O as green solvent, Eosin Y as organic photocatalyst, and ambient air as oxidant enables a metal-free, reliable synthesis of α,β-unsaturated ketones from methyl arenes and aromatic alkynes. This reaction offers high efficiency, use of green solvents, metal-free nature, environmental friendliness, and visible light as a renewable energy source.
A. K. Kushwaha, A. Kamal, H. K. Singh, S. K. Maury, T. Mondal, S. Singh, Org. Lett., 2024, 26, 1416-1420.

A simple, efficient, and environmentally beneficient disulfide-catalyzed photocatalytic regioselective oxidative cleavage of 1-arylbutadienes to cinnamaldehydes offers mild reaction conditions, excellent regioselectivity, and compatibility with a wide range of functional groups.
R. A. Fernandes, P. Kumar, A. Bhowmik, D. A. Gorve, Org. Lett., 2022, 24, 3436-3439.

Iron(III) sulfate mediates a simple and efficient regioselective oxidative cleavage of 1-arylbutadienes in the presence of oxygen. The reaction offers good yields, excellent regioselectivity, and good functional group tolerance.
A. Bhowmik, R. A. Fernandes, Org. Lett., 2019, 21, 9203-9207.

A palladium-catalyzed oxidative dehydrogenation enables an efficient synthesis of 1,4-enediones from saturated ketones in the presence of molecular oxygen as the sole oxidant. This atom- and step-economic process offers broad substrate scope, good functional group tolerance, and complete E-stereoselectivity.
B.-Y. Zhao, X.-L. Zhang, R.-L. Guo, M.-Y. Wang, Y.-R. Gao, Y.-Q. Wang, Org. Lett., 2021, 23, 1216-1221.

The combination of hypervalent iodine(III) and TMSN₃ promotes an oxidative cleavage of C-C double bonds of enamides under an air atmosphere. This method exhibits good functional group tolerance, broad substrate scope and mild conditions. The reaction also offers an approach to cyanobenzamides with synthetic potential for the preparation of industrial and pharmaceutical nitrogen- and oxygen-containing molecules.
G. Liu, Y. Li, J. Sheng, X.-S. Wang, Synthesis, 2017, 49, 3968-3974.

A visible-light-driven photoredox-catalyzed nonaqueous oxidative C-N cleavage of N,N-dibenzylanilines provides 2° amides. The protocol also enables the conversion of 2-(dibenzylamino)benzamide to quinazolinones in the presence of (NH₄)₂S₂O₈ as an additive.
N. Neerathilingam, M. B. Reddy, R. Anandhan, J. Org. Chem., 2021, 86, 15117-15127.

An oxidative carbonylation of aryl boronic acids with inert tertiary amines provides tertiary amides via C(sp³)-N bond activation. This efficient protocol significantly restricts the formation of the homocoupling biarylketone product.
Y. A. Kolekar, B. M. Bhanage, J. Org. Chem., 2021, 86, 14028-14035.

An aerobic acetoxyhydroxylation of alkenes is cooperatively catalyzed by organic nitrite and palladium at room temperature using clean and cheap air as the sole oxidant. Various vicinal diols, diacetoxyalkanes, and dihalogenoalkanes have been synthesized.
X.-M. Chen, X.-S. Ning, Y.-B. Kang, Org. Lett., 2016, 18, 5368-5371.

A photo-on-demand in situ synthesis of chloroformates of primary alkyl alcohols in the presence of CHCl₃ and oxygen followed by addition of alcohols or amines enables a one-pot synthesis of carbonates and carbamates, respectively.
F. Liang, M. Yanai, Y. Suzuki, A. Tsuda, Org. Lett., 2020, 22, 3566-3569.

Eosin Y catalyzes a highly efficient benzylic hydroperoxidation using an energy-economical light source (blue LED), and a sustainable oxidant (molecular oxygen). Primary, secondary, and tertiary hydroperoxides as well as silyl, benzyl, and acyl peroxides were successfully prepared with good yields and excellent functional group compatibility.
J. Inoa, M. Patel, G. Dominici, R. Eldabagh, A. Patel, J. Lee, Y. Xing, J. Org. Chem., 2020, 85, 6181-6187.

A flexible metal-free cascade reaction involving aerobic C(sp³)-H hydroxylation and decarbonylation introduces valuable secondary alcohol groups at the α-position of N-aryl amides with high regioselectivity and functional group tolerance.
X. Zhang, Y. Yu, W. Li, L. Shi, H. Li, J. Org. Chem., 2022, 87, 16263-16275.

A cyanide-catalyzed ring-expansion of cyclic α-hydroxy-β-oxoesters provides δ-valerolactone derivatives in up to quantitative yields. Several alkyl-substituted as well as benzo- and heteroarene-annulated starting materials are converted without problems. As an additional benefit, the substrates are straightforwardly accessed by cerium-catalyzed aerobic α-hydroxylation of readily available β-oxoesters.
D. Kieslich, J. Christoffers, Org. Lett., 2021, 23, 953-957.

CuF₂/DMAP is as an excellent catalytic system for vinylsilane-promoted N-vinylation of amides and azoles at room temperature without an external fluoride source. Valuable monomers for water-soluble polymers, viz., NVP, NVC, and NVIBA, were synthesized on a gram scale.
K. Mondal, S. Patra, P. Halder, N. Mukhopadhyay, P. Das, Org. Lett., 2023, 25, 1235-1240.

A visible light-promoted and tertiary-amine-assisted hydroxysulfenylation of both electron-rich and electron-deficient alkenes with thiophenols provides β-hydroxysulfides in very good yields. This simple and sustainable approach features mild reaction conditions, high efficiency, and excellent functional group tolerance.
J. Shi, X.-W. Gao, Q.-X. Tong, J.-J. Zhong, J. Org. Chem., 2021, 86, 12922-12931.

A metal-free quinoid catalyst, namely 1-hexylKuQuinone (KuQ), promotes a chemoselective, light-induced thioether to sulfoxide oxidation in HFIP, using O₂ as the oxidant, at room temperature. Remarkably, the system can be recharged and recycled without loss of activity and selectivity.
M. Forchetta, F. Sabuzi, L. Stella, V. Conte, P. Galloni, J. Org. Chem., 2022, 87, 14016-14025.

An environmentally friendly and operationally simple DBU-catalyzed aerobic cross-dehydrogenative coupling (CDC) reaction provides thiolated products of (hetero)aryl acetates, (hetero)aryl ketones, and indoles in good yields.
X. Jia, X. Ma, W.-F. J.-Q. Zhang, Y. Zhao, B. Guo, L. Tang, Y.-Y. Yang, J. Org. Chem., 2022, 87, 16492-16505.

A visible light mediated sulfurization of alkenes and alkynes with aromatic and heteroaromatic thiols enables a benign and metal-free functionalization using Eosin Y as photocatalyst and eco-friendly air (O₂) as the sole oxidant. This selective approach shows good substrate generality to afford sulfoxides, β-hydroxysulfoxides, and β-keto sulfides in high yield.
R. Rahaman, M. T. Hoque, D. K. Maiti, Org. Lett., 2022, 24, 6885-6890.

NH-Sulfonimidamides are prepared in good yields by a ligand-free copper-catalyzed coupling of primary sulfinamides with secondary amines in the presence of air as the terminal oxidant. The reaction occurs at room temperature and shows good functional group tolerance. A sulfanenitrile is proposed as an intermediate in this oxidative amination.
P. Wu, J. Demaerel, D. Kong, D. Ma, C. Bolm, Org. Lett., 2022, 24, 6988-6992.

Ethyl bromodifluoroacetate as carbonyl source enables an efficient direct carbonation of aromatic acids to yield monoalkyl phthalate derivatives in good yields. A broad range of substrates bearing various functional groups were tolerated.
N. Tao, J. Wang, C. Yuan, R. Zeng, Y.-S. Zhao, Org. Lett., 2019, 21, 8607-8610.

A mild and operationally simple copper-catalyzed vinylogous aerobic oxidation of β,γ- and α,β-unsaturated esters features good yields, broad substrate scope, excellent chemo- and regioselectivity, and good functional group tolerance. This method is additionally capable of oxidizing β,γ- and α,β-unsaturated aldehydes, ketones, amides, nitriles, and sulfones.
H.-J. Zhang, A. W. Schuppe, S.-T. Pan, J.-X. Chen, B.-R. Wang, T. R. Newhouse, L. Yin, J. Am. Chem. Soc., 2018, 140, 5300-5310.

The combination of Fe(III), l-valine, and 4-OH-TEMPO catalyzes an oxidation of alcohols followed by condensation with sulfinamide or sulfonamide in one pot to provide N-sulfinyl- and N-sulfonyl imines under mild conditions in very good yields.
G. Zhang, Y. Xing, S. Xu, C. Ring, S. Shan, Synlett, 2018, 29, 1232-1238.

An aerobic boron Heck reaction with cyclobutene forms exclusively linear 1-aryl-1,3-dienes using (hetero)arylboronic acids, or 1,3,5-trienes using alkenylboronic acids, rather than typical Heck products (i.e., substituted cyclobutenes).
N. J. McAlpine, L. Wang, B. P. Carrow, J. Am. Chem. Soc., 2018, 140, 13634-13639.

A convenient visible-light-induced reaction of isocyanides, thiols, and water under mild reaction conditions provides various thiocarbamates in good yields in the presence of cheap Rose Bengal as the photocatalyst.
W. Wei, P. Bao, H. Yue, S. Liu, L. Wang, Y. Li, D. Yang, Org. Lett., 2018, 20, 5291-5295.

An efficient copper-catalyzed oxidative amination of sulfenamides provides sulfinamidines in the presence of air as the terminal oxidant. A diverse array of secondary and primary amines can be efficiently transformed into their corresponding products. This method is well-suited for last-stage functionalization and offers exceptional chemoselectivity, mild conditions, and facile operation.
G. Huang, J. Ye, M. Tan, Y. Chen, X. Lu, J. Org. Chem., 2023, 88, 16116-16121.

The use of chiral α-alkyl N-tert-butanesulfinyl imidates and α-aryl N′-tert-butanesulfinyl amidines enables a diastereoselective α-hydroxylation using molecular oxygen. The aza-enolates generated from deprotonation of the imidates/amidines react with O₂ followed by transformation into α-hydroxylation products in the presence of trimethyl phosphite as reductant.
P.-J. Ma, H. Liu, Y.-J. Xu, H. A. Aisa, C.-D. Lu, Org. Lett., 2018, 20, 1236-1239.

Aldehyde α-hydroperoxides can be accessed from α-substituted acroleins with triethylsilane and water under Pd/C catalysis and aerobic conditions via a Pd/C-catalyzed conjugate reduction step and a subsequent hydroperoxidation step. Upon reduction, 2,2-disubstituted 1,2-diols are obtained.
S. Tuokko, P. M. Pihko, Synlett, 2016, 27, 1649-1652.

A cobalt-catalyzed peroxidation of silyl enol ethers with molecular oxygen and triethylsilane provides silyl monoperoxyketals in good yield. These compounds serve as precursors to peroxycarbenium ions, which undergo annulations to provide 1,2-dioxolanes.
B. Hurlocker, M. R. Miner, K. A. Woerpel, Org. Lett., 2014, 16, 4280-4283.

Aryl radicals generated in situ from arene diazonium fluoroborates promoted by ascorbic acid enable a convenient and general oxidative arylation of vinyl arenes in air at room temperature in the absence of any additive and visible light irradiation. Various 2-aryl acetophenones have been obtained in good yields.
B. Majhi, D. Kundu, B. C. Ranu, J. Org. Chem., 2015, 80, 7739-7745.

A metal-free and green catalytic system enables an oxyfluorination of olefins for the synthesis of α-fluoroketones which is an important building block for organic synthesis. Moreover, this reaction system exhibits great functional group tolerance.
Q. Yang, L.-L. Mao, B. Yang, S.-D. Yang, Org. Lett., 2014, 16, 3460-3463.

Pd/C along with NaBH₄ in aqueous ethanol or methanol and either K₂CO₃ or KOH as base at room temperature under molecular oxygen or air is capable of oxidizing alcohols to its desired carbonyl or carboxyl counterpart. Room temperature reaction in aqueous system and recyclability of the catalyst make the process safe and cheaper.
G. An, H. Ahn, K. A. De Castro, H. Rhee, Synthesis, 2010, 477-485.

N. Jiang, A. J. Ragauskas, J. Org. Chem., 2007, 72, 7030-7033.

The use of a NaOtBu-O₂ resulted in an efficient oxidative cleavage of vic-1,2-diols to form carboxylic acids in high yields. The present protocol is a green alternative to conventional transition metal based methods. Large-scale production with nonchromatographic purification is also possible.
S. M. Kim, D. W. Kim, J. W. Yang, Org. Lett., 2014, 16, 2876-2879.

A modular Cu/ABNO catalyst system enables efficient aerobic oxidative coupling of alcohols and amines to amides. All four permutations of benzylic/aliphatic alcohols and primary/secondary amines are viable in this reaction, enabling broad access to secondary and tertiary amides with excellent functional group compatibility within short reaction time at rt.
S. L. Zultanski, J. Zhao, S. S. Stahl, J. Am. Chem. Soc., 2016, 138, 6416-6419.

A copper-catalyzed aerobic oxidative decarboxylation of phenylacetic acids and α-hydroxyphenylacetic acids enables the synthesis of aromatic carbonyl compounds via decarboxylation, dioxygen activation, and C-H bond oxidation steps in a one-pot protocol with molecular oxygen as the sole terminal oxidant.
Q. Feng, Q. Song, J. Org. Chem., 2014, 79, 1867-1871.

The visible-light mediated oxidative C-C bond cleavage of aldehydes has been achieved in good yields at ambient temperature and open to air using Ru(bpy)₃Cl₂ as the photoredox catalyst.
H. Sun, C. Yang, F. Gao, Z. Li, W. Xia, Org. Lett., 2013, 15, 624-627.

A visible light-induced photocatalysis enables a general and practical decarboxylative hydroxylation of a broad range of carboxylic acids using molecular oxygen as the green oxidant. NaBH₄ as additive reduces unstable peroxyl radical intermediates in situ.
S. N. Khan, M. K. Zaman, R. Li, Z. Sun, J. Org. Chem., 2020, 85, 5019-5026.

A photocatalytic direct decarboxylative hydroxylation of carboxylic acids enables the conversion of various readily available carboxylic acids to alcohols in good yields under extremely mild reaction conditions using molecular oxygen as a green oxidant and visible light as a driving force.
H.-T. Song, W. Ding, Q.-Q. Zhou, J. Liu, L.-Q. Lu, W.-J. Xiao, J. Org. Chem., 2016, 81, 7250-7255.

A facile synthesis of aryl carboxylic acids from aryl ketones by aerobic photooxidation using the inexpensive and easily handled CBr₄ as catalyst is applicable to inert compounds under usual photo-irradiation conditions, and appears very attractive for the expansion of the Norrish Type I reaction.
S.-i. Hirashima, T. Nobuta, N. Tada, A. Itoh, Synlett, 2009, 2017-2019.

A facile and mild photooxidation of alcohols gives carboxylic acids and ketones using easily handled 2-chloroanthraquinone as an organocatalyst under visible light irradiation in an air atmosphere.
Y. Shimada, K. Hattori, N. Tada, T. Miura, A. Itoh, Synthesis, 2013, 45, 2684-2688.

Screening of simple binary and ternary admixtures of Pd/charcoal in combination with one or two metal and/or metalloid components as the catalyst for aerobic oxidative methyl esterification of primary alcohols revealed two very effective catalyst compositions. One was used in batch aerobic oxidation reactions, whereas the other achieved nearly 60 000 turnovers in a continuous-flow packed-bed reactor with no apparent loss of catalytic activity.
D. S. Mannel, M. S. Ahmed, T. W. Root, S. S. Stahl, J. Am. Chem. Soc., 2017, 139, 1690-1698.

A readily accessible catalyst system consisting of Pd/charcoal in combination with bismuth(III) nitrate and tellurium metal enables an efficient aerobic oxidative methyl esterification of primary alcohols, exhibits a broad substrate scope, and is effective with both activated and unactivated alcohols bearing diverse functional groups. The Bi and Te additives significantly increase the reaction rate, selectivity, and overall product yields.
A. B. Powell, S. S. Stahl, Org. Lett., 2013, 15, 5072-5075.

In a Cu-catalyzed aerobic oxidative esterification of simple ketones via C-C bond cleavage, various common ketones, even inactive aryl long-chain alkyl ketones, are selectively converted into esters. The reaction tolerates a wide range of alcohols, including primary and secondary alcohols, chiral alcohols with retention of the configuration and electron-deficient phenols.
X. Huang, X. Li, M. Zou, S. Song, C. Tang, Y. Yuan, N. Jiao, J. Am. Chem. Soc., 2014, 136, 14858-14865.

A chemoselective oxidation of α-hydroxy acids to α-keto acids is catalyzed by 2-azaadamantane N-oxyl (AZADO), a nitroxyl radical catalyst. The use of molecular oxygen as a cooxidant enables the desired chemoselective oxidation to α-keto acids, that are labile and can easily release CO₂ under oxidation conditions.
K. Furukawa, H. Inada, M. Shibuya, Y. Yamamoto, Org. Lett., 2016, 18, 4230-4233.

Copper-catalyzed aerobic oxidative esterification of acetophenones with alcohols using molecular oxygen gives a broad range of α-ketoesters in good yields. Mechanism studies evealed that the carbonyl oxygen in the ester mainly originated from dioxygen.
X. Xu, W. Ding, Y. Lin, Q. Song, Org. Lett., 2015, 17, 516-519.

Visible light promotes a green and mild conversion of β-ketonitriles into α-ketoesters under catalyst-free conditions via singlet oxygen generation, oxidative C-H bond functionalization, and C-C σ-bond cleavage.
C. Xu, N.-N. Zhang, X.-j. Li, Y.-q. Ge, P.-h. Diao, C. Guo, Synlett, 2018, 29, 1065-1070.

A photoinduced oxidative formylation of N,N-dimethylanilines with molecular oxygen in the absence of an external photocatalyst provided formamides in good yields under mild reaction conditions.
S. Yang, P. Li, Z. Wang, L. Wang, Org. Lett., 2017, 19, 3386-3389.

A copper-catalyzed one-pot strategy for the synthesis of α-ketoamides from 1-arylethanols is highly efficient and delivers product in very good yields via alcohol oxidation, sp³ C-H oxidation, and oxidative amidation.
N. Sharma, S. S. Kotha, N. Lahiri, G. Sekar, Synthesis, 2015, 47, 726-736.

Benzylimidates can directly be converted to primary α-ketoamides by using molecular oxygen as an oxidant in the presence of copper(II) salt. The reaction offers a wide substrate scope and operationally mild conditions.
Y. Kumar, M. Shaw, R. Thakur, A. Kumar, J. Org. Chem., 2016, 81, 6617-6625.

N-Hydroxyphthalimide (NHPI) mediates a mild electrochemical α-oxygenation of a wide range of linear and cyclic benzamides in an undivided cell using O₂ as the oxygen source and 2,4,6-trimethylpyridine perchlorate as an electrolyte.
F. Bai, N. Wang, Y. Bai, X. Ma, C. Gu, B. Dai, J. Chen, J. Org. Chem., 2023, 88, 2985-2998.

An eco-friendly and mild aerobic oxidation of allylic alcohols using Fe(NO₃)₃·9H₂O/TEMPO/NaCl as catalysts under atmospheric pressure of oxygen at room temperature provides a convenient pathway to the synthesis of stereodefined α,β-unsaturated enals or enones with the retention of the double-bond configuration.
J. Liu, S. Ma, Org. Lett., 2013, 15, 5150-5153.

A method for generating (E)-α,β-unsaturated aldehydes from Z- or E-allylic alcohols involves a Cu-catalyzed oxidation followed by an organocatalytic Z/E-isomerization with N,N-dimethylaminopyridine (DMAP).
D. Könning, W. Hiller, M. Christmann, Org. Lett., 2012, 14, 5258-5261.

The combination of a copper-catalyzed oxidation in the presence of oxygen, a deprotonation, and a Wittig reaction enables the synthesis of α,β-unsaturated esters, ketones, and nitriles from alcohols and functionalized phosphonium salts. The solvent mixture of acetonitrile and formamide (1:1) is optimized for all part reactions.
W. Ding, J. Hu, H. Jin, X. Yu, S. Wang, Synthesis, 2018, 50, 107-118.

A combination of pyrenedione (PD) and KOtBu achieves a facile alcohol dehydrogenation under visible-light excitation in the presence of aerobic oxygen as the terminal oxidant. The resulting carbonyl compounds can be easily converted to vinyl nitriles in a single-pot reaction. This environmentally benign, organocatalytic α-olefination of nitriles operates at low temperature.
A. K. Bains, Y. Ankit, D. Adhikari, Org. Lett., 2021, 23, 2019-2023.

A method for the synthesis of secondary thiocarbamates from readily available isocyanides and thiosulfonates with broad functional group tolerance proceeds under mild reaction conditions in isopropanol and is catalyzed by inexpensive sodium iodide.
P. Mampuys, Y. Zhu, S. Sergeyev, E. Ruijter, R. V. A. Orru, S. Van Doorslaer, B. U. W. Maes, Org. Lett., 2016, 18, 2808-2811.

A practical aerobic oxidation of propargylic alcohols using Fe(NO₃)₃•9H₂O, TEMPO and sodium chloride in toluene at room temperature allows the conversion of propargylic alcohols to α,β-unsaturated alkynals or alkynones in good to excellent yields. This protocol can also be applied in industrial-scale production.
J. Liu, X. Xie, S. Ma, Synthesis, 2012, 44, 1569-1576.

Pd/C-catalyzed oxidative alkoxycarbonylation of terminal alkynes using alcohols in the presence of tetrabutylammonium iodide under CO/O₂ gave α,β-alkynyl esters and unsymmetrical maleate esters in very good yields depending on the reaction conditions. The protocols eliminate the use of phosphine ligands and offer catalyst recovery. The catalyst was recycled up to six times without significant loss of catalytic activity.
S. T. Gadge, B. M. Bhanage, Synlett, 2013, 24, 981-986.

A fluoroform-derived CuCF₃ reagent can be prepared in large quantities and is convenient to use. This reagent, prepared from inexpensive industrial waste fluoroform (CF₃H), enables an efficient trifluoromethylation reaction of alkynes in presence of the diamine ligand tetramethylethylenediamine (TMEDA).
L. He, G. C. Tsui, Org. Lett., 2016, 18, 2800-2803.

Allylic alcohols were oxidized into aldehydes or ketones in the presence of oxygen and Et₃N using Pd(OAc)₂ as catalyst. Diols with one allylic function were selectively oxidized, with one of the hydroxyl groups remaining untouched.
F. Batt, E. Bourcet, Y. Kassab, F. Fache, Synlett, 2007, 1869-1872.

Adsorbed [RuCl₂(p-cymene)]₂ on activated carbon is an efficient, environmentally attractive and highly selective catalyst for use in aerobic oxidations, hydrolytic oxidations and dehydrations. The heterogeneous catalyst was recovered quantitatively by simple filtration and could be reused with minimal loss of activity.
E. Choi, C. Lee, Y. Na, S. Chang, Org. Lett., 2002, 4, 2369-2371.

An aerobic oxidation of primary and secondary alcohols to aldehydes and ketones using TEMPO-CuCl as catalyst in the ionic liquid [bmin][PF₆] has been developed. The system needs no bubbling of O₂ due to its good solubility in the ionic liquid. The resulting aldehydes (with no traces of carboxylic acids) and ketones can be extracted with organic solvents. The ionic liquid can be reused after washing with water and drying under high vacuum (8 runs for the oxidation of benzyl alcohol: yields of 72%, 70, 68, 70, 65, 64, 62, and 60).
I. A. Ansari, R. Gree, Org. Lett., 2001, 1507-1509.

A four-component system consisting of acetamido-TEMPO/Cu(ClO₄)₂/TMDP/DABCO in DMSO allows an efficient room-temperature aerobic alcohol oxidation of various alcohols into their corresponding aldehydes or ketones in good to excellent yields. The catalytic system can be recycled.
N. Jiang, A. J. Ragauskas, J. Org. Chem., 2006, 71, 7087-7090.

The system Cu(ClO₄)₂/acetamido-TEMPO/DMAP catalyses the room-temperature aerobic oxidation of primary alcohols to aldehydes in the ionic liquid [bmpy]PF₆. The catalysts can be recycled and reused.
N. Jiang, A. J. Ragauskas, Org. Lett., 2005, 7, 3689-3692.

1 mol-% TEMPO and a catalytic amount of 1,3-dibromo-5,5-dimethylhydantoin and NaNO₂ is a highly efficient catalytic system for the aerobic oxidations of benzylic alcohols in water.
R. Liu, C. Dong, X. Liang, X. Wang, X. Hu, J. Org. Chem., 2005, 70, 239-244.

Oxidation of alcohols to aldehydes and ketones were performed under atmospheric oxygen with a catalytic amount of V₂O₅ in toluene at 100°C. Secondary alcohols can be chemoselectively converted into ketones in the presence of primary hydroxy groups.
S. Velusamy, T. Punniyamurthy, Org. Lett., 2004, 6, 217-219.

An I₂-catalyzed hydroxylation of β-dicarbonyl moieties using air as the oxidant under photoirradiation gives α-hydroxy-β-dicarbonyl compounds. With α-unsubstituted malonates, the hydroxylated dimerization product was afforded as the predominant product along with a minor product, α,α-dihydroxyl malonate.
C.-B. Miao, Y.-H. Wang, M.-L. Xing, X.-W. Lu, X.-Q. Sun, H.-T. Yang, J. Org. Chem., 2013, 78, 11584-11589.

An efficient method for the 2-hydroxylation of 1,3-diketones by using inexpensive atmospheric oxygen as an oxidant under transition-metal-free and ecofriendly conditions provides products in high yields.
Z. Li, T. Li, J. Li, L. He, X. Jia, J. Yang, Synlett, 2015, 26, 2863-2865.

An efficient and economical ligand-free palladium-based oxidation system using molecular oxygen as the sole oxidant enables the Tsuji-Wacker oxidation of terminal olefins and especially styrenes to methyl ketones. In addition, this system achieves a tandem Wacker oxidation-dehydrogenation sequence of terminal olefins to yield α,β-unsaturated ketones.
Y.-F. Wang, Y.-R. Gao, S. Mao, Y.-L. Zhang, D.-D. Guo, Z.-L. Yan, S.-H. Guo, Y.-Q. Wang, Org. Lett., 2014, 16, 1610-1613.

The merger of aerobic oxidative Cu catalysis with decarboxylative enolate interception enables a decarboxylative carbonyl α-arylation of arylboron nucleophiles with malonic acid derivatives. This method converts substrates containing electrophilic functional groups that are incompatible with existing α-arylation methods.
P. J. Moon, S. Yin, R. J. Lundgren, J. Am. Chem. Soc., 2016, 138, 13826-13829.

A general, highly selective asymmetric redox-relay oxidative Heck reaction using achiral or racemic acyclic alkenols and boronic acids delivers remotely functionalized arylated carbonyl products, with excellent enantioselectivity under mild conditions, bearing a range of useful functionality. The regioselectivity of the initial migratory insertion depends on the electronic nature of the boronic acid.
T.-S. Mei, E. W. Werner, A. J. Burckle, M. S. Sigman, J. Am. Chem. Soc., 2013, 135, 6830-6833.

The copper-catalyzed highly regioselective reaction of aryl alkyl alkynes and arylpropargylic alcohols with diaryliodonium salts gives α-arylketones in good yields under mild conditions. Depending on the internal alkyne substrate, two different arylation-oxygenation pathways under different reaction conditions have been elaborated based on deuterated experiments, controlling experiments, and spectroscopic analysis of reaction intermediates.
Z.-F. Xu, C.-X. Cai, J.-T. Liu, Org. Lett., 2013, 15, 2096-2099.

A catalytic oxidative cleavage of 1,3-diketones enables the synthesis of the corresponding carboxylic acids by aerobic photooxidation with iodine under irradiation with a high-pressure mercury lamp.
N. Tada, M. Shomura, L. Cui, T. Nobuta, T. Miura, A. Itho, Synlett, 2011, 2896-2900.

An aerobic photooxidative cleavage of vicinal diols yields carboxylic acids using 2-chloroanthraquinone in the presence of photoirradiation with a high-pressure mercury lamp. This is a metal-free reaction in which molecular oxygen is used as the terminal oxidant.
Y. Matsusaki, T. Yamaguchi, N. Tada, T. Miura, A. Itoh, Synlett, 2012, 23, 2059-2062.

An efficient oxidation of various acetals, including open-chain acetals, 1,3-dioxanes and 1,3-dioxalanes, with molecular oxygen in the presence of catalytic amounts of N-hydroxyphthalimide (NHPI) and Co(OAc)₂ as co-catalyst gave esters.
B. Karimi, J. Rajabi, Synthesis, 2003, 2373-2377.

Natural sunlight and air enable an efficient oxidation of α-aryl halogen derivatives to the corresponding α-aryl carbonyl compounds at room temperature through the combination of photocatalysis and organocatalysis. A plausible mechanism was proposed on the basis of the mechanistic studies.
Y. Su, L. Zhang, N. Jiao, Org. Lett., 2011, 13, 2168-2171.

Heterogeneous nitrogen-doped carbon-incarcerated iron/copper bimetallic nanoparticle (NP) catalysts showed a high activity for aerobic ammoxidation of alcohols to nitriles.
T. Yasukawa, X. Yang, S. Kobayashi, J. Org. Chem., 2020, 85, 7543-7548.

A green, practical, convenient, and cheap copper-catalyzed oxidative coupling of aromatic alcohols and acetonitrile to β-ketonitriles involves a C-C coupling with loss of two hydrogen atoms from the corresponding two carbons, using oxygen as the terminal oxidant.
J. Shen, D. Yang, Y. Liu, S. Qin, J. Zhang, J. Sun, C. Liu, C. Liu, X. Zhao, C. Chu, R. Liu, Org. Lett., 2014, 16, 350-353.

N-hydroxyphthalimide (NHPI) catalyzes a metal-free, aerobic oxidative cleavage of olefins. This methodology avoids the use of toxic metals or overstoichiometric amounts of traditional oxidants, showing good economical and environmental advantages. Based on the experimental observations, a plausible mechanism is proposed.
R. Lin, F. Chen, N. Jiao, Org. Lett., 2012, 14, 4158-4161.

The cheap and readily available organic dye eosin Y as photocatalyst enables the oxidation of alkynes using air as the oxidant under metal-free conditions upon irradiation with blue light to provide dicarbonylation products in good yields. Some oxidation-sensitive groups, such as formyl and a carbon-carbon double bond, were tolerated under the reaction conditions.
X. Liu, T. Cong, P. Liu, P. Sun, J. Org. Chem., 2016, 81, 7256-7261.

A Wacker-type oxidation of alkynes catalyzed by PdBr₂ and CuBr₂ allows an efficient access to 1,2-diketones using molecular oxygen. Under optimized conditions, various alkynes give 1,2-diketones in good yield. The mechanism of this reaction was preliminarily investigated by control experiments.
W. Ren, Y. Xia, S.-J. Ji, Y. Zhang, X. Wan, J. Zhao, Org. Lett., 2009, 11, 1841-1844.

A combination of copper powder and Selectfluor generates a cationic copper species that efficiently catalyze the formation of 1,2-diketones from alkynes under mild conditions with water and dioxygen as inexpensive and environmentally benign sources of oxygen.
W. Zhang, J. Zhang, Y. Liu, Z. Xu, Synlett, 2013, 24, 2709-2714

The presence of catalytic amounts of carbon tetrabromide enables an aerobic photooxidative cleavage of carbon-carbon triple bonds to carboxylic acids under photoirradiation.
T. Yamaguchi, T. Nobuta, Y. Kudo, S.-i. Hirashima, N. Tada, T. Miura, A. Itoh, Synlett, 2013, 24, 607-610.

Aerobic oxidation of deoxybenzoins is efficiently catalyzed by 1,4-diazabicyclo[2.2.2]octane (DABCO) with air as the sole oxidant to give the corresponding benzils in excellent yields. The process has been successfully extended to a one-pot synthesis of quinoxalines from benzyl ketones and aromatic 1,2-diamines.
C. Qi, H. Jiang, L. Huang, Z. Chen, H. Chen, Synthesis, 2011, 387-396.

A copper-promoted intramolecular C-H oxidative amination reaction between secondary amine (N-H) and C(sp³)-H at the benzylic position of azaarenes or α-position of ketones enables the synthesis of aziridine derivatives in the presence of oxygen as sole oxidant. Moreover, a Yb(OTf)₃-CuI relay system catalyzes the aziridination of electron-deficient vinylarenes with unprotected primary alkyl amines.
Y.-D. Du, Z.-J. Xu, C.-Y. Zhou, C.-M. Che, Org. Lett., 2019, 21, 895-899.

An efficient aerobic linear allylic C-H amination under palladium(II)/bis-sulfoxide/Brønsted base catalysis operates under operationally simple conditions (1 equiv of olefin, 1 atm O₂ or air) with reduced catalyst loadings while providing higher turnovers and product yields than systems employing stoichiometric benzoquinone (BQ) as the terminal oxidant.
C. P. Pattillo, I. I. Strambeanu, P. Calleja, N. A. Vermeulen, T. Mizuno, M. C. White, J. Am. Chem. Soc., 2016, 138, 1265-1272.

An oxidative amidation of aromatic aldehydes in the presence of low loadings of phenazine ethosulfate as an inexpensive metal-free visible light photocatalyst proceeds at ambient temperature and uses air as the sole oxidant. The operationally easy procedure provides an economical, green, and mild alternative for the formation of amide bonds.
D. Leow, Org. Lett., 2014, 16, 5812-5815.

A Cu-catalyzed oxidative amidation-diketonization reaction of terminal alkynes leads to α-ketoamides. In this copper-catalyzed radical process, O₂ not only participates as the ideal oxidant but also undergoes dioxygen activation under ambient conditions.
C. Zhang, N. Jiao, J. Am. Chem. Soc., 2010, 132, 28-29.

A copper-catalyzed aerobic oxidative cross-dehydrogenative coupling (CDC) of amines with α-carbonyl aldehydes leads to various α-ketoamides compounds. Many types of amines are tolerant in this transformation. Wide substrate scope, and the use of air as oxidant and initiator make this transformation highly efficient and practical.
C. Zhang, X. Zong, L. Zhang, N. Jiao, Org. Lett., 2012, 14, 3280-3283.

An efficient, mild Pd-catalyzed oxidative coupling of aromatic primary amines and alkenes under molecular oxygen provides a rapid access to (Z)-enamines with exceptional functional group tolerance and excellent regio- and stereoselectivity. The resultant enamines could be conveniently transformed into a series of N-containing heterocycles, thus illustrating its potential applications in synthetic and medicinal chemistry.
X. Ji, H. Huang, W. Wu, X. Li, H. Jiang, J. Org. Chem., 2013, 78, 11155-11162.

A copper-catalyzed four-component formal oxyaminalization of alkenes with Togni's reagent and amines in the presence of molecular oxygen as both the oxidant and oxygen source efficiently provides a range of structurally diverse α-oxoketene aminals. This simple procedure offers excellent functional group tolerance, broad substrate scope, and mild conditions.
L. Wang, C. Qi, T. Guo, H. Jiang, Org. Lett., 2019, 21, 2223-2226.

A clay-supported copper nitrate (Claycop) and a catalytic amount of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl enable an inexpensive and mild reagent system for the nitration of a wide variety of aromatic and aliphatic olefins. High conversions and exclusive E-selectivity, together with the environmentally benign nature of the Claycop reagent, make this a green method and an attractive alternative to established methods.
E. Begari, C. Singh, U. Nookaraju, P. Kumar, Synlett, 2014, 25, 1997-2000.

In situ aerobic dual oxidation with asymmetric organocatalysis enables an enantioselective synthesis of α-hydrazino aldehydes from alcohols and N-Boc hydrazine instead of the conventional combination of aldehydes with azodicarboxylates. This reaction tolerates various substituents on the alcohol component and features excellent enantiocontrol, cheap starting materials, operational simplicity, and scalability.
Z. Cui, D.-M. Du, Org. Lett., 2016, 18, 5616-5619.

A highly efficient palladium-catalyzed cross-coupling of arenethiols and arylhydrazines with molecular oxygen as the sole oxidant provides unsymmetrical diaryl sulfides. The only byproducts are water and nitrogen. The reaction tolerates a broad range of functional groups, including reactive iodides.
C. Wang, Z. Zhang, Y. Tu, Y. Li, J. Wu, J. Zhao, J. Org. Chem., 2018, 83, 2389-2394.

Molecular iodine catalyzes a facile and practical synthesis of thiocarbamates in good yields from readily available sodium sulfinates, isocyanides, and water. The present methodology offers favorable functional group tolerance and the use of odorless sodium sulfinates.
P. Bao, L. Wang, H. Yue, Y. Shao, J. Wen, D. Yang, Y. Zhao, H. Wang, W. Wei, J. Org. Chem., 2019, 84, 2976-2983.

An electrochemical oxidative coupling of thiophenols and alcohols provides sulfinic esters in the presence of O₂ (air) as the oxygen source smoothly at room temperature.
H. Zhou, J. Duan, D. Xie, J. Yang, B. Ma, G. Wang, C. Wu, X.-C. Wang, Synthesis, 2020, 52, 2705-2712.

A mild and environmentally friendly visible-light-mediated additive-free decarboxylative functionalization of acrylic acids in the presence of ammonium thiocyanate, the inexpensive organic dye 9,10-dicyanoanthracene as a photocatalyst, and dioxygen as both an oxygen source and an oxidant provides a series of important α-thiocyanate ketones.
Z.-L. Wang, J. Chen, Y.-H. He, Z. Guan, J. Org. Chem., 2021, 86, 3741-3749.

With Ni(OAc)₂ as catalyst, an oxidative coupling of thiols and phosphonates to phosphorothioates with oxygen as oxidant proceeded very sluggishly with low yield, whereas adding non-redox-active metal ions such as Y³⁺ dramatically promoted the catalytic efficiency. Y(OTf)₃ can obviously accelerate the activation of thiols by Ni(II) and next accelerate its reaction with phosphonate.
J.-W. Xue, M. Zeng, S. Zhang, Z. Chen, G. Yin, J. Org. Chem., 2019, 84, 4179-4190.

A copper-catalyzed decarboxylative coupling of sulfoximines with aryl propiolic acids enables the preparation of N-alkynylated sulfoximines. Various substituents on both the sulfoximidoyl moiety as well as the aryl group of the propiolic acid were tolerated.
D. L. Priebbenow, P. Becker, C. Bolm, Org. Lett., 2013, 15, 6155-6157.

A recyclable ionic liquid supported organotelluride catalyzes an aerobic oxidation of phosphite esters to phosphate esters. This method offers high conversion rates and allows a ready isolation of the resulting products. The catalyst can be reused.
A. Mihoya, Y. Shibuya, A. Ito, A. Toyoda, M. Oba, S. Koguchi Synlett, 2020, 31, 2043-2045.

Iodine/base-catalyzed aerobic photooxidation of 1,3-diketones under visible-light irradiation of fluorescent lamp enables a catalytic direct synthesis of 1,2-diketones.
N. Tada, M. Shomura, H. Nakayama, T. Miura, A. Itoh, Synlett, 2010, 1979-1983.

Pd(DMSO)₂(TFA)₂ as a catalyst enables a direct dehydrogenation of cyclohexanones and other cyclic ketones to the corresponding enones, using O₂ as the oxidant. α,β-Unsaturated carbonyl compounds are versatile intermediates in the synthesis of pharmaceuticals and biologically active compounds. The substrate scope includes heterocyclic ketones and several natural-product precursors.
T. Diao, S. S. Stahl, J. Am. Chem. Soc., 2011, 133, 14566-14569.

Silyl enol ethers can serve as masked source of saturated ketones to derive β-aryl enones and their derivatives by dehydrosilylation to generate enones in situ and subsequent oxidative arylation with arylboronic acids using relayed Pd(II) catalysis in one pot under base-free conditions in the presence of oxygen as efficient and green oxidant.
R. R. Polimera, A. Ilangovan, M. A. M. Subbaiah, J. Org. Chem., 2023, 88, 7256-7271.

Use of 4,5-diazafluorenone as an ancillary ligand for Pd(OAc)₂ enables terminal alkenes to be converted to linear allylic acetoxylation products in good yields and selectivity under O₂. Mechanistic studies have revealed that the ligand facilitates C-O reductive elimination from a π-allyl-PdII intermediate, thereby eliminating the requirement for benzoquinone as stoichiometric oxidant in this key catalytic step.
A. N. Campbell, P. B. White, I. A. Guzei, S. S. Stahl, J. Am. Chem. Soc., 2010, 132, 15116-15119.

The cooperative interaction of a diselane and a photoredox catalyst enables a metal-free protocol for the oxidative coupling of nonactivated alkenes with simple carboxylic acids in ambient air or pure O₂ as the terminal oxidant. A range of both functionalized and nonfunctionalized alkenes can be readily converted into the corresponding allylic ester with good yields and excellent regioselectivity as well as good functional group tolerance.
S. Ortgies, C. Depken, A. Breder, Org. Lett., 2016, 18, 2856-2859.

Phenyliodonium diacetate mediates a synthesis of α-oxygenated ketones from styrenes in the presence of molecular oxygen and N-hydroxyphthalimide or N-hydroxybenzotriazole under metal-free conditions. The present method is applicable for wide range of styrenes with various functional groups.
S. Samanta, R. R. Donthiri, C. Ravi, S. Adimurthy, J. Org. Chem., 2016, 81, 3457-3463.

A mild copper-catalyzed Chan-Lam-Evans type cross-coupling reaction enables a stereospecific and regioselective preparation of enol esters from carboxylate salts or carboxylic acids and potassium alkenyltrifluoroborate salts in the presence of oxygen, catalytic CuBr, DMAP and 4 Å molecular sieves. Overall, this method demonstrates carboxylic acids as suitable reaction partners for nondecarboxylative copper-catalyzed cross-couplings.
F. Huang, T. D. Quach, R. A. Batey, Org. Lett., 2013, 15, 3058-3061.

A photoinduced oxidative N-dealkylation method for both aryl tertiary amines and amides was achieved in an alkaline environment under mild conditions accompanied by excellent functional group tolerance.
Q. Lian, J. Chen, K. Huang, K. Hou, J. Fang, W. Wei, J. Zhou, Org. Lett., 2023, 25, 8387-8392.

A Cu₂O-catalyzed aerobic oxidative decarboxylative ammoxidation of phenylacetic acids and α-hydroxyphenylacetic acids enables the synthesis of various primary benzamides in good yields. This one-pot domino protocol combines decarboxylation, dioxygen activation, oxidative C-H bond functionalization, and amidation reactions.
Q. Song, Q. Feng, K. Yang, Org. Lett., 2014, 16, 624-627.

A metal- and photocatalyst-free room-temperature amidation of amines with feedstock phenacyl bromides provides α-ketoamides using molecular oxygen as an oxidant as well as a source of oxygen. This visible light mediated and base-promoted reaction offers good functional group tolerance (benzylic alcohol, keto, cyano, nitro, halo, etc.), a broad substrate scope, and gram-scale synthesis.
S. Das, S. Mondal, S. P. Midya, S. Mondal, E. Ghosh, P. Ghosh, J. Org. Chem., 2023, 88, 14847-14859.

Imines and secondary amines were synthesized selectively by a Pd-catalyzed one-pot reaction of benzyl alcohols with primary amines. The reactions did not require any additives and were effective for a wide range of alcohols and amines.
M. S. Kwon, S. Kim, S. Park, W. Bosco, R. K. Chidrala, J. Park, J. Org. Chem., 2009, 74, 2877-2879.

A modular aerobic oxidation of amines to imines has been achieved using an ortho-naphthoquinone (o-NQ) catalyst. Whereas the cooperative catalyst system of o-NQ and Cu(OAc)₂ provided homocoupled imines from benzylamines, the presence of TFA helped the formation of cross-coupled imines in excellent yields. The oxidation of secondary amines to imines or ketimines is facilitated with the help of Ag₂CO₃ as cocatalyst.
Y. Goriya, H. Y. Kim, K. Oh, Org. Lett., 2016, 18, 5174-5177.

Iron-catalyzed aerobic oxidative reactions of primary amines, secondary amines, benzylamines with anilines, and alcohols with amines in the presence of air as the economic and safe oxidant, provide several direct, practical, and greener approaches for the preparation of useful imines.
E. Zhang, H. Tian, S. Xu, X. Yu, Q. Xu, Org. Lett., 2013, 15, 2704-2707.

The use of photosensitive C₇₀ for the catalytic oxidation of benzylamines to the corresponding imines enables faster reaction rates, lower catalyst loadings, and clean reactions with simple workup without chromatography, compared to C₆₀ or other commonly used photosensitizers such as tetraphenylporphyrin (TPP). Singlet oxygen (¹O₂) and the superoxide radical anion (O₂^•–) act as important reactive species in this oxidation.
R. Kumar, E. H. Gleißner, E. G. V. Tiu, Y. Yamakoshi, Org. Lett., 2016, 18, 184-187.

A base-mediated protocol enables the synthesis of imines and amines from N-phenylureas and alcohols in good yields under air. This protocol is as an efficient alternative to conventional methods for the synthesis of imines and amines.
D. K. T. Yadav, B. M. Bhanage, Synlett, 2014, 25, 1611-1615.

Cu-catalyzed aerobic oxidative three-component coupling of a terminal alkyne, secondary amine, and sulfonamide enables an efficient synthesis of amidines. The use of Cu(OTf)₂ as catalyst produces amidines selectively via an initial oxidative coupling of the terminal alkyne with the secondary amine, followed by hydroamidation of the ynamine intermediate with the sulfonamide. Glaser-Hay alkyne homocoupling products are not observed.
J. Kim, S. S. Stahl, J. Org. Chem., 2015, 80, 2448-2454.

A general, efficient, and metal-free method for aerobic oxidation of primary benzylamines to the corresponding oximes in good yields is catalyzed by N,N′,N″-trihydroxyisocyanuric acid in the presence of acetaldoxime and water as solvent. This practical method uses air as economic and green oxidant, water as green solvent, and tolerates a wide range of substrates.
J. Yu, M. Lu, Synlett, 2014, 25, 1873-1878.

The synthesis of alkyl 2-phenylazocarboxylates largely depended on the stoichiometric use of toxic oxidants. The use of CuCl and DMAP as catalysts enables an environment-friendly aerobic oxidation of alkyl 2-phenylhydrazinecarboxylates to alkyl 2-phenylazocarboxylates under mild conditions.
M. H. Kim, J. Kim, J. Org. Chem., 2018, 83, 1673-1679.

A mild, aerobic, catalytic synthesis of nitriles directly from alcohols and aqueous ammonia proceeds via a dehydrogenation cascade mediated by catalytic CuI, bpy, and TEMPO in the presence of oxygen. The substrate scope includes various functionalized aromatic and aliphatic alcohols. This protocol also enabled a one-pot synthesis of various biaryl heterocycles directly from commercially available alcohols.
W. Yin, C. Wang, H. Huang, Org. Lett., 2013, 15, 1850-1853.

In the presence of a catalytic amount of 4-AcNH-TEMPO, NaNO₂, and HNO₃, benzaldehydes underwent condensation with NH₄OAc and a subsequent aerobic oxidation to produce nitriles selectively under O₂. Aerobic oxidative conversion of a primary alcohol is also achieved.
J.-H. Noh, J. Kim, J. Org. Chem., 2015, 80, 11624-11628.

A copper-promoted C≡N triple bond cleavage of coordinated cyanide anion under a dioxygen atmosphere enables a nitrogen transfer to various aldehydes via a single electron-transfer process. This protocol provides a new cleavage pattern for the cyanide ion and maybe a more useful synthetic pathway to nitriles from aldehydes.
Q. Wu, Y. Luo, A. Lei, J. You, J. Am. Chem. Soc., 2016, 138, 2885-2888.

Cu(I) as promoter enables simple strategies for decarboxylative functionalizations of electron-deficient benzoic acids under aerobic conditions. For the conversion of electron-rich benzoic acids, Pd(II) must be used as catalyst. The method provides aryl halides (-I, Br, and Cl) in the presence of readily available halogen sources CuX (X = I, Br, Cl) and benzonitriles in the presence of nontoxic and low-cost K₄Fe(CN)₆.
Z. Fu, Z. Li, Y. Song, R. Yang, Y. Liu, H. Cai, J. Org. Chem., 2016, 81, 2794-2803.

In the presence of catalytic copper(II) bromide, a direct α-amination of ketones, esters, and aldehydes takes place to produce synthetically useful α-amino-substituted motifs. The transformation is proposed to proceed via a catalytically generated α-bromo carbonyl species followed by nucleophilic displacement of the bromide by the amine, which delivers the α-amino carbonyl adduct while the catalyst is reconstituted.
R. W. Evans. J. R. Zbieg, S. Wu, W. Li, D. W. C. MacMillan, J. Am. Chem. Soc., 2013, 135, 16074-16077.

In an efficient Mn-catalyzed aerobic oxidative hydroxyazidation of olefins for synthesis of β-azido alcohols, an aerobic oxidative generation of azido radical is a key process. The reaction offers broad substrate scope, the use of an inexpensive Mn-catalyst, high efficiency, easy operation under air, and mild conditions at room temperature.
X. Sun, X. Li, S. Song, Y. Zhu, Y.-F. Liang, N. Jiao, J. Am. Chem. Soc., 2015, 137, 6059-6066.

Various tertiary β-trifluoromethyl alcohols can be synthesized in good yields without transition metal catalysts via a radical trifluoromethylation of alkenes using in situ generated peroxide in NMP under O₂ as the radical initiator.
C. Liu, Q. Lu, Z. Huang, J. Zhang, F. Liao, P. Peng, A. Lei, Org. Lett., 2015, 17, 6034-6037.

A visible light-mediated photocatalytic decarboxylative oxyphosphorylation of cinnamic acids with diarylphosphine oxides provides the corresponding β-ketophosphine oxides under mild conditions.
H.-F. Qian, C.-K. Li, Z.-H. Zhou, Z.-K. Tao, A. Shoberu, J.-P. Zou, Org. Lett., 2018, 20, 5947-5951.

Pd(II)-catalyzed ortho-hydroxylation of variously substituted benzoic acids under an athmospheric pressure of oxygen or air is achieved under nonacidic conditions. Labeling studies support a direct oxygenation of aryl C-H bonds with molecular oxygen.
Y.-H. Zhang, J.-Q. Yu, J. Am. Chem. Soc., 2009, 131, 14654-14655.

The use of flavin organocatalysts and a Hantzsch ester enabled a transition-metal-free Dakin oxidation fueled by molecular oxygen as the terminal oxidant. Catechols and electron-rich phenols are achieved with low catalyst loadings, in the presence of Hantzsch ester, and O₂ or air as the stoichiometric oxidant source.
S. Chen, F. W. Foss, Jr, Org. Lett., 2012, 14, 5150-5153.

A general and efficient aerobic oxidative hydroxylation of arylboronic acids promoted by benzoquinone provides phenols in very good yields. The main advantages of this protocol are the use of water as solvent in the presence of a catalytic amount of benzoquinone under metal-free conditions.
G. Chen, X. Zeng, X. Cui, Synthesis, 2014, 46, 263-268.

A water-soluble photocatalyst promotes an aerobic oxidative hydroxylation of arylboronic acids to furnish phenols in excellent yields. This transformation uses visible-light irradiation under environmentally friendly conditions.
H.-Y. Xie, L.-S. Han, S. Huang, X. Lei, Y. Cheng, W. Zhao, H. Sun, X. Wen, Q.-L. Xu, J. Org. Chem., 2017, 82, 5236-5241.

In a useful synthesis of phenols from arylboronic acids, hydrogen peroxide is generated in situ by aerobic photooxidation using visible-light irradiation and easily handled 2-chloroanthraquinone as an organocatalyst. The mild, metal- and base-free conditions enable an environmentally benign approach to the synthesis of phenols from arylboronic acids.
K. Matsui, T. Ishigami, T. Yamaguchi, E. Yamaguchi, N. Tada, T. Miura, A. Itoh, Synlett, 2014, 25, 2613-2616.

Passerini three-component reaction under catalytic aerobic conditions allows the conversion of alcohols instead of aldehydes. The reaction of alcohols, isocyanides, and carboxylic acids in toluene in the presence of a catalytic amount of cupric chloride, NaNO₂, and TEMPO afforded, under an oxygen atmosphere, the P-3CR adducts in good yields.
J. Brioche, G. Masson, J. Zhu, Org. Lett., 2010, 12, 1432-1435.

A simple iridium/copper relay catalysis system enables a direct aerobic α,β-dehydrogenation of γ,δ-unsaturated amides and carboxylic acids to provide conjugated dienamides and dienoic acids in excellent yield. Instead of α-C-H metalation, this reaction proceeds by β-C-H activation, which results in enhanced α-acidity.
Z. Whang, Z. He, L. Zhang, Y. Huang, J. Am. Chem. Soc., 2018, 140, 735-740.

Oxidative ring expansion of methylenecyclopropanes with CAN under oxygen atmosphere was investigated. A facile conversion affording 2,2-diarylcyclobutanones occurred in good yields.
V. Nair, T. D. Suja, K. Mohanan, Synthesis, 2006, 2531-2534.

A new copper-catalyzed oxidative [3 + 2] cycloaddition of alkenes with anhydrides using oxygen as the sole oxidant affords γ-lactones in good to excellent yield. This catalyzed cyclization process has a broad substrate scope.
L. Huang, H. Jiang, C. Qi, X. Liu, J. Am. Chem. Soc., 2010, 132, 17652-17654.

The use of 2,4,6-triphenylpyrylium tetrafluoroborate (TPT) as catalyst allows a regiocontrolled construction of cyclic ethers and lactones via visible-light-induced intramolecular C-O bond formation. This approach provides valuable five- and six-membered cyclic ethers and lactones with a unified protocol.
H. Im, D. Kang, S. Choi, S. Shin, S. Hong, Org. Lett., 2018, 20, 7437-7441.

Cu/nitroxyl catalysts promote a highly efficient and selective aerobic oxidative lactonization of diols under mild reaction conditions using ambient air as the oxidant. A Cu/ABNO catalyst system shows excellent reactivity with symmetrical diols and hindered unsymmetrical diols, whereas a Cu/TEMPO catalyst system displays excellent chemo- and regioselectivity for the oxidation of less hindered unsymmetrical diols.
X. Xie, S. S. Stahl, J. Am. Chem. Soc., 2015, 137, 3767-3770.

Several Pd-catalyzed oxidative cyclizations proceed in excellent yield under simple aerobic conditions. Importantly, this system provided entry into enatioselective catalysis with a readily available Pd-sparteine complex.
R. M. Trend, Y. K. Ramtohul, E. M. Ferreira, B. Stoltz, Angew. Chem. Int. Ed., 2003, 42, 2892-2895.

Enantioselective intramolecular oxidative amidation of alkenes has been achieved using a (pyrox)Pd(II)(TFA)₂ as catalyst and O₂ as the stoichiometric oxidant. The reactions proceed at room temperature in very good yields and with high enantioselectivity. Catalyst-controlled stereoselective cyclization reactions are demonstrated for a number of chiral substrates.
R. I. McDonald, P. W. White, A. B. Weinstein, C. P. Tam, S. S. Stahl, Org. Lett., 2011, 13, 2830-2833.

Use of a base-free Pd(DMSO)₂(TFA)₂ catalyst enables the synthesis of six-membered nitrogen heterocycles via a Wacker-type aerobic oxidative cyclization of alkenes. Various heterocycles, including morpholines, piperidines, piperazines and piperazinones, are accessible by this method.
Z. Lu, S. S. Stahl, Org. Lett., 2012, 14, 1234-1237.

An operationally simple and rapid copper-catalyzed three-component synthesis of trisubstituted N-aryl guanidines involving cyanamides, arylboronic acids, and amines is performed in the presence of K₂CO₃, a catalytic amount of CuCl₂·2H₂O, bipyridine, and oxygen (1 atm).
J. Li, L. Neuville, Org. Lett., 2013, 15, 6124-6127.

In the presence of oxygen and a small amount of AIBN as radical initiator, primary amines are oxidatively coupled to imines and tertiary amines are cyanated to α-aminonitriles. These metal-free aerobic oxidative coupling reactions may find applications in a wide range of green oxidation chemistry.
L. Liu, Z. Wang, X. Fu, C.-H. Yan, Org. Lett., 2012, 14, 5692-5695.

A dioxygenation of alkenes using molecular oxygen and a simple, readily prepared hydroxamic acid derivative in th presence of a radical initiator offers an alternative to common dioxygenation processes catalyzed by precious transition metals. This transformation capitalizes on the unique reactivity profile of hydroxamic acid derivatives in radical-mediated alkene addition processes.
B. C. Giglio, V. A. Schmidt, E. J. Alexanian, J. Am. Chem. Soc., 2011, 133, 13320-13322.

The chemoselectivity of sulfide oxidation was simply controlled by reaction temperature and the use of O₂/air as the terminal oxidant and oxygen source to provide aryl sulfones and sulfoxides. This convenient system offers broad substrate scope and easy realization of gram-scale production.
Z. Cheng, P. Sun, A. Tang, W. Jin, C. Liu, Org. Lett., 2019, 21, 8925-8929.

An organodiselenide catalyzed the aerobic oxidation of thiols into disulfides in practical yields without any reagents/additives, base, and light source. The synthesized diselenide also catalyzes the reduction of hydrogen peroxide into water.
V. Rathore, A. Upadhyay, S. Kumar, Org. Lett., 2018, 20, 6274-6278.

The combination of a riboflavin-derived organocatalyst and molecular iodine successfully promoted the aerobic oxidation of thiols to disulfides under metal-free mild conditions at room temperature. The the biomimetic flavin catalyst enables the transfer of electrons from the iodine forming the basis for a green oxidative synthesis of disulfides from thiols.
M. Oka, R. Kozako, H. Iida, Synlett, 2021, 32, 1227-1230.

The arylthiolated Au₂₅(F-Ph)₁₈^- nanocluster is synthesized and characterized. Ligands avoid distortion of the geometric structure, limit the Jahn-Teller effect, and protect the nanocluster from oxidization. The low energy gap (HOMO-LUMO) of the synthetic clusters enables photocatalytic oxidative functionalization reactions mediated by near-infrared light (850 nm).
S. Wang, L. Tang, B. Cai, Z. Yin, Y. Li, L. Xiong, X. Kang, J. Xuan, Y. Pei, M. Zhu, J. Am. Chem. Soc., 2022, 144, 3787-3792.

A copper-catalyzed aerobic decarboxylative sulfonylation of alkenyl carboxylic acids with sodium sulfinates offers an expedient strategy for stereoselective synthesis of (E)-alkenyl sulfones that are widely present in biologically active natural products and therapeutic agents. The transformation proceeds via a radical process and exhibits a broad substrate scope and good functional group tolerance.
Q. Jiang, B. Xu, J. Jia, A. Zhao, Y.-R. Zhao, Y.-Y. Li, N.-N. He, C.-C. Guo, J. Org. Chem., 2014, 79, 7372-7379.

Reactions of cinnamic acids with aromatic sulfinic acid sodium salts in the presence of a catalytic amount of manganese(II) acetate tetrahydrate in dimethyl sulfoxide provide vinyl sulfones in very good yields. The use of DMSO as solvent and the presence of air are critical in achieving good yields.
N. Xue, R. Guo, X. Tu, W. Luo, W. Deng, J. Xiang, Synlett, 2016, 27, 2695-2698.

A nickel-catalyzed hydroxysulfonylation of alkenes using sodium sulfinates under air enabled the selective synthesis of β-hydroxysulfones in good yields and suppressed the formation of β-ketosulfones. On the contrary, sulfonylation of alkynes with sodium sulfonates afforded only β-ketosulfones.
N. Taniguchi, J. Org. Chem., 2015, 80, 7797-7802.

In an unprecedented oxidative radical process, dioxygen as the solely terminal oxidant triggers an aerobic oxidative difunctionalization of terminal alkynes toward β-keto sulfones with high selectivity. IR experiments revealed that pyridine not only acts as a base to successfully surpress ATRA (atom transfer radical addition) process, but also plays a vital role in reducing the activity of sulfinic acids.
Q. Lu, J. Zhang, G. Zhao, Y. Qi, H. Wang, A. Lei, J. Am. Chem. Soc., 2013, 135, 11481-11484.

An efficient one-pot multistep strategy comprising auto-oxidative difunctionalization of alkenes, oxidation of sulfides, and a further reduction of peroxides enables the synthesis of complex β-hydroxysulfone derivatives from thiophenols and alkenes. This method offers readily available substrates, low-cost and environmental benign reagents, nontoxic and renewable solvents, and mild reaction conditions.
Y. Wang, W. Jiang, C. Huo, J. Org. Chem., 2017, 82, 10628-10634.

An iron-catalyzed sulfonylation of aryl enol acetates with sulfonyl hydrazides enables the construction of β-keto sulfones under aerobic conditions. This environmentally benign approach utilizes an inexpensive iron salt as the catalyst, readily available sulfonyl hydrazides as the sulfonylating reagents, and air as oxidant under mild conditions.
V. K. Yadav, V. P. Srivastava, L. D. S. Yadav, Synlett, 2016, 27, 427-431.

A mild diazenylation of active methylene compounds and N-heterocyclic compounds with arylhydrazine hydrochlorides is mediated by iodine under basic aerobic conditions. The reaction could be executed either under heating or in the presence of blue LED light.
D. S. Barak, S. U. Dighe, I. Avasthi, S. Batra, J. Org. Chem., 2018, 83, 3361-3366.

A diaryldiselenide catalyzes a cross-dehydrogenative nucleophilic functionalization of hydrophosphoryl compounds. Phosphorus and selenium NMR studies reveal the existence of a P-Se bond intermediate, and structural analyses indicate a stereospecific reaction.
Handoko, Z. Benslimane, P. S. Arora, Org. Lett., 2020, 22, 5806-5810.

n the presence of a catalytic amount of Pd(TFA)₂ and a chiral Pyox ligand, an oxidative Heck reaction between arylboronic acids and 4-substituted or 4,4-disubstituted cyclopent-1-enes provides arylated products with concurrent creation of two stereocenters in good yields with excellent diastereo- and enantioselectivities under an atmosphere of oxygen.
G. Chen, J. Cao, Q. Wang, J. Zhu, Org. Lett., 2020, 22, 322-325.

An efficient base-catalyzed [3 + 3] oxidative aromatization of α,β-unsaturated carbonyl compounds with dimethyl glutaconate under mild, metal-free conditions affords substituted benzenes in high to excellent yields with oxygen as oxidant and water as sole byproduct. In situ generation of the α,β-unsaturated carbonyl compounds from aldehydes and ketones enables a more convenient tandem [3 + 2 + 1] aerobic oxidative aromatization reaction.
A. Diallo, Y.-L. Zhao, H. Wang, S.-S. Li, C.-Q. Ren, Q. Liu, Org. Lett., 2012, 14, 5776-5779.

Pd-catalyzed intermolecular aerobic dehydrogenative aromatizations enable the arylation of amines with cyclohexanones and 2-cyclohexen-1-ones. Under optimized reaction conditions, primary and secondary amines are selectively arylated in good yields under an atmosphere of molecular oxygen.
S. A. Girard, X. Hu, T. Knauber, F. Zhou, M.-O. Simon, G.-J. Deng, C.-J. Li, Org. Lett., 2012, 14, 5606-5609.

A nitrite-catalyzed ring contraction reaction of substituted tetrahydropyrans provides 2-acyltetrahydrofurans in good yields via a dehydrogenative dual functionalization under aerobic conditions. On the other hand, the oxidation reaction of 1-substituted isochromans occurred via a bromohydroxylation to give 1-(dibromoalkyl)-1-hydroxyisochromans in high yields.
K. Watanabe, T. Hamada, K. Moriyama, Org. Lett., 2018, 20, 5803-5807.

A metal-free photoredox system, consisting of an acridinium photocatalyst, an organic base, and molecular sieve (MS) 4 Å, promotes chemoselective photooxidation of aryl alkenes in the presence of oxygen. This oxo-acyloxylation of aryl alkenes provides a green, practical, and metal-free protocol for a wide range of α-acyloxy ketones.
Q.-B. Zhang, Y.-L. Ban, D.-G. Zhou, P.-P. Zhou, L.-Z. Wu, Q. Liu, Org. Lett., 2016, 18, 5256-5259.

A convenient and efficient reaction of carbohydrazides with diazo-substituted hypervalent iodine reagents provides highly functionalized diazirines. The method is mild, robust, and highly selective, which successfully converted a variety of aryl, alkyl, benzyl, and heterocyclic hydrazides into the corresponding diazirine derivatives.
M. A. Ansari, G. Kumar, M. S. Singh, Org. Lett., 2022, 24, 2815-2820.

A silver-catalyzed hydroamination of tosyl-protected N-allylguanidines provides substituted cyclic guanidines in high yields. The reactions can be used for construction of quaternary stereocenters as well as both monocyclic and bicyclic guanidine products.
Z. J. Garlets, M. Silvi, J. P. Wolfe, Org. Lett., 2016, 18, 2331-2334.

An oxidative relay Heck arylation reaction enables the construction of chiral α,β-unsaturated δ-lactams, widely used as pharmacophores, in high yields and excellent enantioselectivities. This strategy also allows facile access to 7-substituted α,β-unsaturated ε-lactam products and δ-lactams.
Q. Yuan, M. S. Sigman, J. Am. Chem. Soc., 2018, 140, 6527-6530.

N-Sulfonyl- and N-acylpyrroles were synthesized via olefin ring-closing metathesis of diallylamines followed by in situ oxidative aromatization in the presence of the ruthenium Grubbs catalyst and a suitable copper catalyst. Under an oxygen atmosphere, the reaction worked smoothly without the need of hydroperoxide oxidants.
W. Chen, Y.-L. Zhang, H.-J. Li, X. Nan, Y. Liu, Y.-C. Wu, Synthesis, 2019, 51, 3651-3666.

One-pot condensations of ketones, aldehydes and hydrazine monohydrochloride readily formed pyrazoline intermediates under mild conditions. In situ oxidation employing bromine afforded a wide variety of pyrazoles in very good yields. Alternatively, a more benign oxidation protocol affords 3,5-disubstituted or 3,4,5-trisubstituted pyrazoles by simply heating pyrazolines in DMSO under oxygen.
V. Lellek, C.-y. Chen, W. Yang, J. Liu, X. Ji, R. Faessler, Synlett, 2018, 29, 1071-1075.

A regioselective, Cu(II)-catalyzed intermolecular annulation of aryl ketones with a wide range of aromatic olefins under ambient air provides multisubstituted furan derivatives in good yields. This protocol is applicable to both cyclic and acyclic aryl ketones.
A. Dey, M. A. Ali, S. Jana, A. Hajra, J. Org. Chem., 2017, 82, 4812-4818.

A copper-mediated intermolecular annulation of alkyl ketones and β-nitrostyrenes enables a regioselective synthesis of multisubstituted furan derivatives in good yields.
M. Ghosh, S. Mishra, A. Hajra, J. Org. Chem., 2015, 80, 5364-5368.

N-tosylhydrazones underwent a copper-mediated [3 + 2] oxidative cyclization reaction to afford 2,3,5-trisubstituted furans in good yields. The method features an inexpensive metal catalyst, readily available substrates, high regioselectivity, and convenient operation.
Y. Huang, X. Li, Y. Yu, C. Zhu, W. Wu, H. Jiang, J. Org. Chem., 2016, 81, 5014-5020.

2-Acyl furans can be constructed from ynenones via a sequential addition of a trialkylphosphine, 5-exo-dig cyclization to form a furan ring, and oxidation of the resulting phosphonium ylide with molecular oxygen. Many common functional groups are tolerated, and the products are obtained in very good yield under mild conditions.
C. Xu, S. Wittmann, M. Gemander, V. Ruohonen, J. S. Clark, Org. Lett., 2017, 19, 3556-3559.

Domino synthesis of tetrasubstituted thiophenes from 1,3-enynes and mercaptoacetaldehyde using DABCO at room temperature offers broad substrate scope and mild reaction conditions. The reaction consists of a Michael addition, 5-exo-dig carboannulation, and oxidation sequence under air.
G. Bharathiraja, G. Sathishkannan, T. Punniyamurthy, J. Org. Chem., 2016, 81, 2670-2674.

A dual catalytic approach offers readily access to substituted heterocycle aldehydes via oxygen radical addition to vinyl-gold intermediates under Fe catalyst assistance. This system offers good functional group compatibility for the synthesis of substituted oxazole, indole, and benzofuran aldehydes.
H. Peng, N. G. Akhmedov, Y.-F. Liang, N. Jiao, X. Shi, J. Am. Chem. Soc., 2015, 137, 8912-8915.

A three-component cyclization of 2H-azirines, alkynyl bromides, and molecular oxygen under visible-light photoredox catalysis at room temperature provides a wide range of substituted oxazoles in good yields.
L . Chen, H. Li, P. Li, L. Wang, Org. Lett., 2016, 18, 3646-3649.

An efficient copper-catalyzed aerobic oxidative dehydrogenative annulation of amines, alkynes, and O₂ provides trisubstituted oxazoles via dioxygen activation and oxidative C-H bond functionalization.
J. Pan, X. Li, X. Qiu, X. Luo, N. Jiao, Org. Lett., 2018, 20, 2762-2765.

The use of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) as catalyst enables a Machetti-De Sarlo reaction of nitroalkenes with alkynes/alkenes under sustainable conditions to afford a library of isoxazole/isoxaline products.
M. Vadivelu, S. Sampath, K. Muthu, K. Karthikeyan, C. Praveen, J. Org. Chem., 2019, 84, 13636-13645.

I₂ promotes a metal-free domino protocol for the one-pot synthesis of 1,3,4-oxadiazoles in good yields via oxidative cleavage of C(sp²)-H or C(sp)-H bonds, followed by cyclization and deacylation. The use of K₂CO₃ is an essential factor in the cyclization and the C-C bond cleavage. This procedure offers good functional group compatibility.
Y. Fan, Y. He, X. Liu, T. Hu, H. Ma, X. Yang, X. Luo, G. Huang, J. Org. Chem., 2016, 81, 6820-6825.

A simple and efficient cationic Fe(III)/TEMPO-catalyzed oxidative cyclization of aroyl hydrazones in the presence of oxygen enables the synthesis of 2,5-disubstituted 1,3,4-oxadiazole derivatives in high yields. The reaction offers a broad scope and good functional-group tolerance.
G. Zhang, Y. Yu, Y. Zhao, X. Xie, C. Ding, Synlett, 2017, 28, 1373-1377.

The auto-oxidation of isobutyraldehyde in the presence of molecular oxygen generates acyloxy radicals, which in situ afford a hypervalent iodine compound with p-anisolyl iodide. A hypervalent iodine mediated reaction of N'-arylidene acetohydrazides provides substituted 1,3,4-oxadiazoles in good yields in parallel.
J. Chauhan, M. K. Ravva, S. Sen, Org. Lett., 2019, 21, 6562-6565.

An iron-catalyzed route for the regioselective synthesis of 1,3- and 1,3,5-substituted pyrazoles from the reaction of diarylhydrazones and vicinal diols allows the conversions of a broad range of substrates.
N. Panda, A. K. Jena, J. Org. Chem., 2012, 77, 9401-9406.

An oxidative, copper-catalyzed, and solvent-free annulation enables a facile synthesis of 2,4,5-triarylated oxazoles at a mild temperature from readily available substrates under an atmosphere of molecular oxygen.
M. Mazibuko, V. Jeena, J. Org. Chem., 2023, 88, 1227-1234.

Practical Cu-catalyzed oxidative, multiple Csp³-H bond cleavage processes achieve a synthesis of thiazoles from simple aldehydes, amines, and element sulfur in the presence of molecular oxygen as a green oxidant.
X. Wang, X. Qiu, J. Wei, J. Liu, S. Song, W. Wang, N. Jiao, Org. Lett., 2018, 20, 2632-2636.

An operationally simple and user-friendly synthesis of 3,5-disubstituted/annulated isothiazoles from β-ketodithioesters/β-ketothioamides and NH₄OAc via C=O/C=S bond functionalization under metal- and catalyst-free conditions. The carbon-economic [4 + 1] annulation relies on a sequential imine formation/cyclization/aerial oxidation cascade forming consecutive C-N and S-N bonds in one pot.
G. Shukla, A. Srivastava, M. S. Singh, Org. Lett., 2016, 18, 2451-2454.

Pyrrole-2-carbaldehydes can efficiently be prepared from aryl methyl ketones, arylamines, and acetoacetate esters via oxidative annulation and C_sp3-H to C=O oxidation in the presence of a copper catalyst, iodine, and oxygen. Mechanistic investigations indicate that the aldehyde oxygen atom originates from oxygen. The reaction avoids the use of stoichiometric quantities of hazardous oxidants.
X. Wu, P. Zhao, X. Geng, C. Wang, Y.-d. Wu, A.-x. Wu, Org. Lett., 2018, 20, 688-691.

An efficient and convenient, copper-catalyzed decarboxylative cycloaddition of propiolic acids, azides, and arylboronic acids provides fully substituted 1,2,3-triazoles from readily available starting materials. A possible mechanism is proposed.
X.-X. Wang, Y. Xin, Y. Li, W.-J. Xia, B. Zhou, R.-R. Ye, Y.-M. Li, J. Org. Chem., 2020, 85, 3576-3586.

A convenient and efficient FeCl₃/I₂-catalyzed aerobic oxidative coupling of amidines and chalcones provides tetrasubstituted imidazoles in high regioselectivity and yields. The reaction offers good functional group tolerance, and mild reaction conditions.
Y. Zhu, C. Li, J. Zhang, M. She, W. Sun, K. Wan, Y. Wang, B. Yin, P. Liu, J. Li, Org. Lett., 2015, 17, 3872-3875.

A facile and versatile catalytic system involving copper catalyst, K₃PO₄ as the base, and O₂ as the oxidant enables an efficient synthesis of 2,4,6-trisubstituted and 2,6-disubstituted 1,3,5-triazines and 1,3-disubstituted 1,2,4-triazoles from amidines with trialkylamines, DMSO, and DMF as the reaction partners, respectively. This protocol features an inexpensive catalyst, a green oxidant, good functional group tolerance, and high regioselectivity.
H. Huang, W. Guo, W. Wu, C.-J. Li, H. Jiang, Org. Lett., 2015, 17, 2894-2897.

A cascade addition-oxidative cyclization of nitriles with 2-aminopyridines or amidines was achieved in the presence of 1,10-phenanthroline-functionalized MCM-41-supported copper(I) complex [Phen-MCM-41-CuBr] as the heterogeneous and recyclable catalyst and air as the oxidant. The approach provides a wide range of 1,2,4-triazole derivatives in high yields.
J. Xia, X. Huang, M. Cai, Synthesis, 2019, 51, 2014-2022.

A direct access to symmetrical and unsymmetrical 2,5-disubstituted [1,3,4]-oxadiazoles has been accomplished through an imine C-H functionalization of N-arylidenearoylhydrazide using a catalytic quantity of Cu(OTf)₂. These reactions can be performed in air atmosphere and moisture making it exceptionally practical for application in organic synthesis.
S. Guin, T. Ghosh, S. K. Rout, A. Banerjee, B. K. Patel, Org. Lett., 2011, 13, 5976-5979.

Efficient palladium-catalyzed sequential isocyanide insertions into N-H and O-H bonds of hydrazides followed by oxidative annulation provide a convenient access to valuable 2-amino-1,3,4-oxadiazoles and their derivatives.
T. Fang, Q. Tan, Z. Ding, B. Liu, B. Xu, Org. Lett., 2014, 16, 2342-2345.

A highly efficient eosin Y catalyzed oxidative heterocyclization of semicarbazones was established under visible-light photoredox catalysis using CBr4 as a bromine source. The protocol renders a rapid, mild, and efficient access to valuable 5-substituted 2-amino-1,3,4-oxadiazoles in an operationally simple way utilizing visible light and atmospheric oxygen.
R. Kapoorr, S. N. Singh, S. Tripathi, L. D. S. Yadav, Synlett, 2015, 26, 1201-1206.

A convenient one-pot Cu(I)-catalyzed strategy gives trisubstituted α-carbonyl furans derivatives in good yields via (2-furyl) carbene complexes using air as the oxidant.
H. Cao, H. Zhan, J. Cen, J. Lin, Y. Lin, Q. Zhu, M. Fu, H. Jiang, Org. Lett., 2013, 15, 1080-1083.

A highly efficient carbon-carbon triple bond cleavage reaction of (Z)-enynols offered a new route to highly substituted butenolides through a gold(I)-catalyzed tandem cyclization/oxidative cleavage.
Y. Liu, F. Song, S. Guo, J. Am. Chem. Soc., 2006, 128, 11332-11333.

An unprecedented C(CO)-C(Ar) bond cleavage of β-enaminones under mild and transition-metal-free conditions followed by 1,3-O/C migration and aerobic hydroxylation provides various 5-hydroxy-1H-pyrrol-2(5H)-ones with broad functional group tolerance.
T. Chen, X. Zhang, W. Wang, Y. Feng, Y. Wang, J. Shen, J. Org. Chem., 2021, 86, 2917-2928.

A copper-catalyzed, practical, and straightforward one-pot synthesis of multisubstituted imidazoles in good yields from arylacetic acids, N-arylbenzamidines, and nitroalkanes involves simultaneous activation of C–H and N–H bonds. The use of inexpensive copper sulfate as a catalyst and readily available starting materials makes this protocol economically viable.
S. D. Pardeshi, P. A. Sathe, K. S. Vadagaonkar, L. Melone, A. C. Chaskar, Synthesis, 2018, 50, 361-370.

An unprecedented ruthenium(II)-catalyzed oxidative C-N coupling method enables a facile intramolecular synthesis of various synthetically challenging tri- and tetrasubstituted pyrazoles in the presence of oxygen as oxidant. The reaction demonstrates excellent reactivity, functional group tolerance, and high yields.
J. Hu, S. Chen, Y. Sun, J. Yang, Y. Rao, Org. Lett., 2012, 14, 5030-5033.

A one-pot, three-component coupling of aldehydes, 1,3-dicarbonyls, and diazo compounds as well as tosyl hydrazones enables an operationally simple and high yielding synthesis of polyfunctional pyrazoles. The reaction proceeds through a tandem Knoevenagel condensation, 1,3-dipolar cycloaddition, and transition metal-free oxidative aromatization reaction sequence utilizing molecular oxygen as a green oxidant.
A. Kamal, K. N. V. Sastry, D. Chandrasekhar, G. S. Mani, P. R. Adiyala, J. B. Nanubolu, K. J. Singarapu, R. A. Maurya, J. Org. Chem., 2015, 80, 4325-4335.

A copper-catalyzed [3 + 2] cycloaddition/oxidation reaction of nitro-olefins with organic azides affords a broad range of 1,4(-NO₂),5-trisubstituted 1,2,3-triazoles with high regioselectivities and in very good yields without elimination of HNO₂.
Y. Chen, G. Nie, Q. Zhang, S. Ma, H. Li, Q. Hu, Org. Lett., 2015, 17, 1118-1121.

Visible light along with 1 mol % cercosporin catalyzes the synthesis of 1,2,3-thiadiazoles and 1,4,5,6-tetrahydropyridazines by a photocatalytic process with good regioselectivity and broad functional-group compatibility under mild conditions in a sustainable, environmentally friendly manner.
Y. Zhang, Y. Cao, L. Lu, S. Zhang, W. Bao, S. Huang, Y. Rao, J. Org. Chem., 2019, 84, 7711-7721.

The use of secondary amines and NXS (X = Cl, Br, I) enables an unprecedented copper-catalyzed oxidative aminohalogenation of electron-deficient maleimides. This simple and green multicomponent reaction offers late-stage modification of drug molecules and in situ formation of N-iodoamines for efficient alkene aminoiodination.
X. Zhou, Y. Yao, C. Wang, Y. Xu, W. Zhang, Y. Ma, G. Wu, Org. Lett., 2021, 23, 3669-3673.

A copper-catalyzed reaction of acetophenones and 1,3-diaminopropane provides direct access to 2-arylpyridines. A range of electronically diverse acetophenones undergo this transformation, affording 2-arylpyridines in good yields.
L.-Y. Xi, R.-Y. Zhang, S. Liang, S.-Y. Chen, X.-Q. Yu, Org. Lett., 2014, 16, 5269-5271.

A convenient base-promoted reaction of 1-arylethylamines with ynones gives polysubstituted pyridines via direct β-C(sp³)-H functionalization of enaminones under metal-free conditions. This procedure features high regioselectivity, high efficiency, and environmental friendliness. Various polysubstituted pyridines were provided in high yields.
J. Shen, D. Cai, C. Kuai, Y. Liu, M. Wei, G. Cheng, X. Cui, J. Org. Chem., 2015, 80, 6584-6589.

A base-promoted intermolecular oxidation C-N bond formation of allylic C(sp³)-H and vinylic C(sp²)-H of allyllic compounds with amidines enables the smooth formation of polysubstituted pyrimidines in the presence of O₂ as the sole oxidant. This protocol features protecting group free nitrogen sources, good functional group tolerance, high atom economy, and environmental advantages.
W. Guo, C. Li, J. Liao, F. Ji, D. Liu, W. Wu, H. Jiang, J. Org. Chem., 2016, 81, 5538-5546.

A simple and efficient method for the base-mediated synthesis of unsymmetrical 1,3,5-triazin-2-amines uses readily available imidates, guanidines, and amides or aldehydes as the starting materials and cesium carbonate as the base. This three-component reaction provides diverse 1,3,5-triazin-2-amines in good yields with tolerance of a broad range of functional groups.
L. Pan, Z. Li, T. Ding, X. Fang, W. Zhang, H. Xu, Y. Xu, J. Org. Chem., 2017, 82, 10043-10050.

The combination of palladium and photoredox catalysis enables an aerobic intramolecular oxidative carbonylation of enamides. The dual catalytic system provides a mild and environmentally friendly method for the synthesis of 1,3-oxazin-6-ones without the use of a stoichiometric amount of hypervalent metal salts.
K. Liu, M. Zou, A. Lei, J. Org. Chem., 2016, 81, 7088-7092.

Inexpensive and reusable graphitic carbon nitride (g-C₃N₄) catalyzes a metal-free synthesis of benzothiazoles via intramolecular C-H functionalization/C-S bond formation under visible-light irradiation. This reaction provides 2-substituted benzothiazoles in high yields under an air atmosphere at room temperature without addition of a strong base or organic oxidizing reagents.
J. Bai, S. Yan, Z. Zhang, Z. Guo, C.-Y. Zhou, Org. Lett., 2021, 23, 4843-4848.

An efficient iron-catalyzed C3-selective formylation of free or N-substituted provides 3-formylindoles in good yields in fairly short reaction times in the presence of formaldehyde and aqueous ammonia, with air as the oxidant. Moreover, this catalytic formylation of indoles can be applied to gram-scale syntheses.
Q.-D. Wang, B. Zhou, J.-M. Yang, D. Fang, J. Ren, B.-B. Zeng, Synlett, 2017, 28, 2670-2674.

An efficient synthesis of diversified indolizine derivatives in good yields from pyridines, methyl ketones and alkenoic acids under solvent-free conditions involves a copper-catalyzed bromination of the methyl ketone, 1,3-dipolar cycloaddition of the pyridinium ylide with the alkenoic acid, followed by oxidative decarboxylation and dehydrogenative aromatization of the primary cycloadduct in oxygen atmosphere.
W. Wang, J. Han, J. Sun, Y. Liu, J. Org. Chem., 2017, 82, 2835-2842.

The combination of flavin and iodine catalyzes an aerobic oxidative C-N bond-forming process for the facile synthesis of imidazo[1,2-a]pyridines. This dual catalytic system can also be applied to the one-pot, three-step synthesis of 3-thioimidazo[1,2-a]pyridines from aminopyridines, ketones, and thiols.
H. Okai, K. Tanimoto, R. Ohkado, H. Iida, Org. Lett., 2020, 22, 8002-8006.

A copper(II)-catalyzed tandem reaction between pyridine ketone and benzylamine proceeded via an efficient condensation-amination-oxidative dehydrogenation process, affording 1,3-diarylated imidazo[1,5-a]pyridines in excellent yields using clean O₂ as an oxidant.
H. Wang, W. Xu, Z. Wang, L. Yu, K. Xu, J. Org. Chem., 2015, 80, 1856-1865.

A zinc iodide catalyzed reaction of 2-aminopyridines and α-amino carbonyl compounds in the presence of oxygen affords 3-aminoimidazo[1,2-a]pyridines in good yields.
X. Han, C. Ma, Z. Wu, G. Huang, Synthesis, 2016, 48, 351-356.

A copper(I)-catalyzed aerobic oxidative coupling of ketoxime acetates with simple pyridines for the synthesis of imidazo[1,2-a]pyridines tolerates a wide range of functional groups and affords a series of valuable imidazo[1,2-a]pyridines in high yields under mild conditions.
Z.-H. Ren, M.-N. Zhao, Y. Yi, Y.-Y. Wang, Z.-H. Guan, Synthesis, 2016, 48, 1920-1926.

A praseodymium-catalyzed aerobic dehydrogenative aromatization of saturated N-heterocycles shows high catalytic activity under mild reaction conditions to produce 7 classes of products with a broad substrate scope.
T. Zhang, Y. Lv, Z. Zhang, Z. Jia, T.-P. Loh, Org. Lett., 2023, 25, 4468-4472.

A transition-metal/quinone complex is an effective catalyst for aerobic dehydrogenation of 3° indolines to the corresponding indoles. The utility of the method is demonstrated in the synthesis of key intermediates to pharmaceutically important molecules.
B. Li, A. E. Wendlandt, S. S. Stahl, Org. Lett., 2019, 21, 1176-1181.

An operationally simple, atom-economic, palladium-catalyzed cyclization reaction of N-aryl imines, affords indoles via an oxidative linkage of two C-H bonds under mild conditions in the presence of oxygen. The process allows quick assembly of indole rings from inexpensive and readily available anilines and ketones and tolerates a broad range of functional groups.
Y. Wei, I. Deb, N. Yoshikai, J. Am. Chem. Soc., 2012, 134, 9098-9101.

Using a scalable and practical synthesis of functionalized indoles via Pd-tBuONO cocatalyzed cycloisomerization of o-allylanilines in the presence of oxygen as a terminal oxidant, a series of substituted indoles were prepared in good yields. The method avoids hazardous oxidants, heavy-metal cocatalysts, and high boiling point solvents such as DMF and DMSO.
X.-S. Ning, M.-M. Wang, J.-P. Qu, Y.-B. Kang, J. Org. Chem., 2018, 83, 13523-13529.

Bioinspired ortho-quinone catalysts have been applied to oxidative synthesis of benzimidazoles, quinoxalines and benzoxazoles from primary amines in high yields under mild conditions with oxygen as the terminal oxidant.
R. Zhang, Y. Qin, L. Zhang, S. Luo, Org. Lett., 2017, 19, 5629-5632.

An efficient oxidative protocol enables the synthesis of multisubstituted or fused tetracyclic benzimidazoles via a metal-free oxidative C-N coupling between the sp³ C-H and free N-H of readily available N¹-benzyl/alkyl-1,2-phenylenediamines in the presence of oxygen and TEMPO.
D. Xue, Y.-Q. Long, J. Org. Chem., 2014, 79, 4727-4734.

An efficient strategy for the synthesis of 3-substituted 2-benzylindoles from stable and readily available o-allylanilines occurred via a regioselective 5-exo-trig intramolecular oxidative cycloisomerization using Pd(OAc)₂ as catalyst and molecular oxygen as an oxidant. The reaction showed a broad substrate scope with good to excellent yields.
R. Nallagonda, M. Rehan, P. Ghorai, Org. Lett., 2014, 16, 4786-4789.

A copper-catalyzed one-pot multicomponent cascade reaction of 1-bromo-2-(2,2-dibromovinyl)benzenes with aldehydes and aqueous ammonia enables a selective synthetis of various indole derivatives. 3-Cyano-1H-indoles, 9H-pyrimido[4,5-b]indoles, or 9H-pyrido[2,3-b]indoles depending on the concentration of ammonia, the molar ratio of reagents, and the structural features of the aldehyde.
B. Li, S. Guo, J. Zhang, X. Zhang, X. Fan, J. Org. Chem., 2015, 80, 5444-5456.

The use of the well-established fluoroform-derived CuCF₃ reagent enables the synthesis of 2-(trifluoromethyl)indoles from easily accessible 2-alkynylanilines via a domino trifluoromethylation/cyclization strategy. 3-formyl-2-(trifluoromethyl)indoles can also be synthesized, which are useful intermediates for the preparation of trifluoromethylated drug analogues.
Y. Ye, K. P. S. Cheung, L. He, G. C. Tsui, Org. Lett., 2018, 20, 1676-1679.

A convenient oxidation of oxindoles with molecular oxygen in the presence of tert-butyl nitrite as an additive enables a mild and metal-free synthesis of isatins without the need for any catalyst or base.
W.-T. Wei, W.-W. Ying, W.-M. Zhu, Y. Wu, Y.-L. Huang, Y.-Q. Cao, Y.-N. Wang, H. Liang, Synlett, 2017, 28, 2307-2310.

An electrochemical oxygenation of indoles provides isatins by merging with a complementary cathode oxygen reduction reaction. This green protocol uses molecular oxygen as the sole oxidant, is free of an an electron transfer mediator, and enables gram-scale preparation.
W. Zhuang, J. Zhang, C. Ma, J. S. Wright, X. Zhang, S.-F. Ni, Q. Huang, Org. Lett., 2022, 24, 4229-4233.

Molecular iodine promoted an efficient synthesis of isatins from 2′-aminophenylacetylenes, 2′-aminostyrenes, and 2′-amino-β-ketoesters via oxidative amidation. The reaction involves iodination, followed by Kornblum oxidation, and intramolecular amidation in one pot.
G. Satish, A. Polu, T. Ramar, A. Ilangovan, J. Org. Chem., 2015, 80, 5167-5175.

A simple electrochemical oxidation of 2'-aminoacetophenones in the presence of n-Bu₄NI provides various isatins with moderate to good yields via C(sp³)-H oxidation followed by intramolecular C-N bond formation. A radical-based pathway is proposed.
P. Qian, J.-H. Su, Y. Wang, M. Bi, Z. Zha, Z. Wang, J. Org. Chem., 2017, 82, 6434-6440.

In a palladium-catalyzed oxidative carbonylation reaction for the synthesis of phthalimides, an imine and H₂O, which are generated in situ from the condensation of aldehyde and amine, serve as self-sufficient directing group and nucleophile, respectively. This method provides rapid access to phthalimides starting from readily available materials with high atom- and step-economy in a one-pot manner.
F. Ji, J. Li, X. Li, W. Guo, W. Wu, H. Jiang, J. Org. Chem., 2018, 83, 104-112.

A Rh/Co relay catalyzed C-H functionalization/annulation of N-aryloxyacetamides with propiolic acids provides valuable benzofuran-3(2H)-one scaffolds with a quaternary center in good yields.
W.-K. Yuan, M.-H. Zhu, R.-S. Geng, G.-Y. Ren, L.-B. Zhang, L.-R. Wen, M. Li, Org. Lett., 2019, 21, 1654-1658.

The combination of iron(III)chloride, tert-butyl nitrite (TBN), and N-hydroxyphthalimide (NHPI) catalyzes a direct aerobic α,β-dehydrogenation of carbonyls. A large variety of lactams and flavanones as well as coumarin and thiochromen-4-one could be produced via this transition-metal-free method in high yields.
G.-Q. Jiang, B.-H. Han, X.-P. Cai, J.-P. Qu, Y.-B. Kang, Org. Lett., 2023, 25, 4429-4433.

The two discrete photochemical activation modes of (-)-riboflavin sequentially induce isomerization and cyclization by energy transfer (ET) and single-electron transfer (SET) activation pathways in an emulation of the coumarin biosynthesis pathway via a key photochemical E → Z isomerization step. The ensuing SET-based cyclization eliminates the need for a prefunctionalized aryl ring.
J. B. Metternich, R. Gilmour, J. Am. Chem. Soc., 2016, 138, 1040-1045.

A heterogeneous cobalt oxide is an effective catalyst for aerobic dehydrogenation of various 1,2,3,4-tetrahydroquinolines to the corresponding quinolines in good yields under mild conditions. Other N-heterocycles are also successfully oxidized to their aromatic counterparts.
A. V. Iosub, S. S. Stahl, Org. Lett., 2015, 17, 4404-4407.

Pd(OAc)₂/2,4,6-Collidine/Brønsted acid catalyze an aerobic oxidative aromatization of simple aliphatic alcohols and anilines to provide diverse substituted quinoline derivatives in high yields with wide functional group tolerance. Practically, the protocol can be easily scaled up to gram-scale.
J. Li, J. Zhang, H. Yang, G. Jiang, J. Org. Chem., 2017, 82, 3245-3251.

Autoxidation of organoboronic acids using 1 atm of O₂ enables a simple, clean, and green carbon-carbon bond formation to provide structurally diverse heteroaromatics with medicinally privileged scaffolds.
L. Zhang, Z.-Q. Liu, Org. Lett., 2017, 19, 6594-9567.

A simple and efficient method enables a direct synthesis of substituted quinolines from anilines and aldehydes through C-H functionalization, C-C/C-N bond formation, and C-C bond cleavage in the presence of air as an oxidant.
R. Yan, X. Liu, C. Pan, X. Zhou, X. Li, X. Kang, G. Huang, Org. Lett., 2013, 15, 4876-4879.

o-Quinone-based catalysts enable an oxidative dehydrogenation of tetrahydroquinolines to afford quinolines. Use of a Co(salophen) cocatalyst allows the reaction to proceed efficiently with ambient air at room temperature. The utility of the catalytic method is demonstrated in the preparation of a number of medicinally relevant quinolines.
A. E. Wendlandt, S. S. Stahl, J. Am. Chem. Soc., 2014, 136, 11910-11913.

A convenient and eco-friendly nickel-catalyzed synthesis of quinoline and quinoxaline via double dehydrogenative coupling starting from 2-aminobenzyl alcohol/1-phenylethanol and diamine/diol, respectively, operates at mild reaction temperatures. The inexpensive molecularly defined catalyst can easly be regenerated under aerobic/O₂ oxidation.
A. K. Bains, V. Singh, D. Adhikari, J. Org. Chem., 2020, 85, 14971-14979.

Singlet diradical Ni(II) featuring two antiferromagnetically coupled singlet diradical diamine type ligands catalyzes simple, straightforward, and atom economic syntheses of quinolines, 2-aminoquinolines, and quinazolines in good yields via biomimetic dehydrogenative condensation/coupling reactions.
G. Chakraborty, R. Sikari, S. Das, R. Mondal, S. Sinha, S. Banerjee, N. D. Paul, J. Org. Chem., 2019, 84, 2626-2641.

In a new benzylation protocol, various 1,2,3,4-tetrahydroquinolines were efficiently converted in combination with aryl aldehydes into β-benzylated quinolines by employing readily available [RuCl₂(p-cymene)]₂ as a catalyst and O₂ as a sole green oxidant. This step- and atom-economic reaction offers excellent functional group tolerance and chemoselectivity.
Z. Tan, H. Jiang, M. Zhang, Org. Lett., 2016, 18, 3154-3157.

A silver-catalyzed sequential formation of two C-C bonds enabels the construction of a series of polysubstituted quinolines from anilines, aldehydes, and alcohols under mild conditions. The transformation is effective for a broad range of substrates, including aliphatic alcohols, arylalkanols, cycloalkanols, and ethylene glycol.
X. Zhang, W. Liu, R. Sun, X. Xu, Z. Wang, Y. Yan, Synlett, 2016, 27, 1563-1568.

A Pd-catalyzed oxidative cyclization of o-vinylanilines and alkynes in the presence of molecular oxygen enables the construction of 2,3-disubstituted quinolines via intermolecular amination of alkyne, insertion of the olefin, and oxidative cleavage of a C-C bond.
J. Zheng, T. Li, L. Huang, W. Wu, J. Li, H. Jiang, Org. Lett., 2016, 18, 3514-3517.

A visible-light induced photocatalytic aerobic oxidative dehydrogenative coupling/aromatization tandem reaction of glycine esters with unactivated alkenes provides quinoline derivatives in good yield under mild and operationally simple reaction conditions.
X. Yang, L. Li, Y. Li, Y. Zhang, J. Org. Chem., 2016, 81, 12433-12442.

A robust and regioselective palladium-catalyzed intermolecular aerobic oxidative cyclization of 2-ethynylanilines with isocyanides enables the synthesis of 4-halo-2-aminoquinolines with good yields and broad substrates scope. Furthermore, this process can be easily extended to synthesis of various 6H-indolo[2,3-b]quinolines via an intramolecular Buchwald-Hartwig cross-coupling reaction in a two-step one-pot manner.
B. Liu, H. Gao, Y. Yu, W. Wu, H. Jiang, J. Org. Chem., 2013, 78, 10319-10328.

A convenient and eco-friendly nickel-catalyzed synthesis of quinoline and quinoxaline via double dehydrogenative coupling starting from 2-aminobenzyl alcohol/1-phenylethanol and diamine/diol, respectively, operates at mild reaction temperatures. The inexpensive molecularly defined catalyst can easly be regenerated under aerobic/O₂ oxidation.
A. K Bains, V. Singh, D. Adhikari, J. Org. Chem., 2020, 85, 14971-14979.

A novel and efficient copper-catalyzed cascade method for the synthesis of quinazolines in good yields uses readily available substituted (2-bromophenyl)methylamines and amidine hydrochlorides as the starting materials, inexpensive CuBr as the catalyst, and economical and environment friendly air as the oxidant. The procedure underwent sequential intermolecular N-arylation, intramolecular nucleophilic substitution and aerobic oxidation.
Q. Liu, Y. Zhao, H. Fu, C. Cheng, Synlett, 2013, 24, 2089-2094.

CuCl/DABCO/4-HO-TEMPO as the catalysts and oxygen as the terminal oxidant enabled an efficient aerobic oxidative synthesis of 2-substituted quinazolines and 4H-3,1-benzoxazines from the one-pot reaction of aldehydes with 2-aminobenzylamines and 2-aminobenzyl alcohols, respectively.
B. Han, X.-L. Yang, C. Wang, Y.-W. Bai, T.-C. Pan, X. Chen, W. Yu, J. Org. Chem., 2012, 77, 1136-1142.

One-pot two-step cyanide-mediated sequential reactions of ortho-phenylenediamines with aldehydes under aerobic oxidation conditions afford 2-aminoquinoxalines in high yields. Various substrates, including aliphatic aldehydes bearing acidic α-protons, are applicable.
Y.-H. Cho, K.-H. Kim, C.-H. Cheon, J. Org. Chem., 2014, 79, 901-907.

Copper(I) catalysis enables a direct transannulation of N-heteroaryl aldehydes or ketones with alkylamines via C_sp³-H amination in the presence of oxygen as the sole oxidant. This transformation provides a rapid and concise access to multifunctional imidazo[1,5-a]pyridines.
M. Li, Y. Xie, Y. Ye, Y. Zou, H. Jiang, W. Zeng, Org. Lett., 2014, 16, 6232-6235.

A set of benzimidazoles, 3H-imidazo[4,5-b]pyridines, purines, xanthines and benzothiazoles was readily prepared from (hetero)aromatic ortho-diamines or ortho-aminothiophenol and aldehydes using chlorotrimethylsilane in DMF as a promoter and water-acceptor agent, followed by oxidation with air oxygen.
S. V. Ryabukhin, A. S. Plaskon, D. M. Volochnyuk, A. A. Tolmachev, Synthesis, 2006, 3715-3726.

The 1H-indazole skeleton can be constructed by a [3 + 2] annulation approach from arynes and hydrazones. Under different reaction conditions, both N-tosylhydrazones and N-aryl/alkylhydrazones can be used to afford various indazoles.
P. Li, C. Wu, J. Zhao, D. C. Rogness, F. Shi, J. Org. Chem., 2012, 77, 3127-3133.

A copper-catalyzed highly selective oxidative coupling-annulation of 2-alkylazaarenes with terminal alkenes provides a simple, efficient, and atom-economic synthesis of indolizines in good yields.
J.-l. Liu, Y.-L. Liang, H.-s. Wang, Y.-m. Pan, Synlett, 2015, 26, 2024-2028.

A CuI-catalyzed aerobic oxidative synthesis of imidazo[1,2-a]pyridines from 2-aminopyridines and acetophenones is compatible with a broad range of functional groups. The reaction also enables the formation of alkenyl-substituted imidazoheterocycles by using unsaturated ketones as substrates. Preliminary mechanistic studies indicate that this reaction proceeds through a catalytic Ortoleva-King reaction.
Y. Zhang, Z. Chen, W. Wu, Y. Zhang, W. Su, J. Org. Chem., 2013, 78, 12494-12504.

An iron-catalyzed synthesis of functionalized indolizines from pyridine and α-substituted allenoate incorporates an annulation followed by an aerobic oxidation.
T. Jin, Z. Tang, J. Hu, H. Yuan, Y. Chen, C. Li, X. Jia, J. Li, Org. Lett., 2018, 20, 413-416.

A rapid, copper-catalyzed aerobic dehydrogenative cyclization of pyridines with ketone oxime esters enables an environmentally friendly synthesis of imidazo[1,2-a]pyridines.
H. Huang, X. Ji, X. Tang, M. Zhang, X. Li, H. Jiang, Org. Lett., 2013, 15, 6218-6221.

The synthesis of functionalized pyrazolo[1,5-a]pyridines through oxidative [3+2] cycloaddition of N-aminopyridines with α,β-unsaturated carbonyl compounds or electron-withdrawing olefins proceeds in N-methylpyrrolidone as the solvent under metal-free conditions at room temperature.
C. Ravi, S. Samanta, D. C. Mohan, N. N. K. Reddy, S. Adimurthy, Synthesis, 2017, 49, 2513-2522.

While an N-S bond coupling/oxidation cascade of N-(2-mercaptophenyl)-N'-substituted ureas provides benzothiadiazin-3-one 1-oxides; the transformation of 2-mercaptobenzamides only occurs via N-S bond coupling to access benzisothiazol-3-ones in good yields. The photochemical syntheses offer mild conditions, excellent chemoselectivity, and functional group compatibility.
H. Li, Z. Xiong, S. Sheng, J. Chen, J. Org. Chem., 2023, 88, 16949-16959.

In a copper-catalyzed synthesis of benzo[d]isothiazol-3(2H)-ones and N-acyl-benzothiazetidine by intramolecular dehydrogenative cyclization, a new nitrogen-sulfur bond is formed by N-H/S-H coupling. The present reaction tolerates various functional groups and gives products in gram scale.
Z. Wang, Y. Kuninobu, M. Kanai, J. Org. Chem., 2013, 78, 7337-7342.

A straightforward synthesis of 2-arylbenzothiazoles from 2-aminothiophenol and aryl aldehydes in air/DMSO oxidant system is operationally simple, proceeds without catalysts, tolerates a wide range of functionalities, and provides desired products in good to excellent yields.
R. Hu, X. Li, Y. Tong, D. Miao, Q. Pan, Z. Jiang, H. Gan, S. Han, Synlett, 2016, 27, 1387-1390.

Copper-catalyzed double C-S bond formation enables a highly efficient synthesis of benzothiazoles from easily available N-benzyl-2-iodoanilines and potassium sulfide via a traditional cross-coupling and an oxidative cross-coupling reaction.
X. Zhang, W. Zeng, Y. Yang, H. Huang, Y. Liang, Org. Lett., 2014, 16, 876-879.

An aerobic visible-light driven photoredox catalytic formation of 2-substituted benzothiazoles through radical cyclization of thioanilides features C-H functionalization and C-S bond formation with no direct metal involvement except the sensitizer. In this reaction, visible-light is the driving force, molecular oxygen the terminal oxidant, and water the only byproduct.
Y. Cheng, J. Yang, Y. Qu, P. Li, Org. Lett., 2012, 14, 98-101.

A Cu(II)-catalyzed oxidative decarboxylation of phenylacetic acids and α-hydroxyphenylacetic acids enables the synthesis of various 2-aryl benzothiazoles in good yields from 2-unsubstituted benzothiazoles in the presence of oxygen as the sole oxidant. The reaction proceeds via Cu(II)-catalyzed decarboxylation, C-H bond oxidation, ring-opening, and condensation steps in one-pot and tolerates various functional groups.
Q. Song, Q. Feng, M. Zhou, Org. Lett., 2013, 15, 5990-5993.

A cascade reaction of isothiocyanatobenzenes with primary or secondary amines provides 2-aminobenzothiazoles using iodine as a catalyst and oxygen as an oxidant via formation of a benzothiourea intermediate followed intramolecular cross dehydrogenative coupling. This method eliminates the use of ortho-halo-substituted precursors, expensive transition-metal catalysts, and hazardous oxidants.
Y. Xu, B. Li, X. Zhang, X. Fan, J. Org. Chem., 2017, 82, 9637-9646.

A cross-dehydrogenative C(sp²)-H amination of indoles is mediated by 2-tert-butylanthraquinone as a photocatalyst, harmless visible light, and aerobic oxygen as the sole oxidant without a transition-metal catalyst and or external oxidant.
T. Yamaguchi, E. Yamaguchi, A. Itoh, Org. Lett., 2017, 19, 1282-1285.

A catalytic amount of iodine enables a metal-free synthesis of 2-aminobenzothiazoles from cyclohexanones and thioureas in the presence of molecular oxygen as the oxidant under mild conditions. Various 2-aminobenzothiazoles, 2-aminonaphtho[2,1-d]thiazoles, and 2-aminonaphtho[1,2-d]thiazoles were prepared in satisfactory yields.
J. Zhao, H. Huang, W. Wu, H. Chen, H. Jiang, Org. Lett., 2013, 15, 2604-2607.

N-Arylthioureas are converted to 2-aminobenzothiazoles via intramolecular C-S bond formation/C-H functionalization in the presence of an unusual cocatalytic Pd(PPh₃)₄/MnO₂ system under an oxygen atmosphere at 80°C. This method eliminates the need for an ortho-halo substituted precursor, instead achieving direct functionalization of the ortho-aryl C-H bond.
L. L. Joyce, R. A. Batey, Org. Lett., 2009, 11, 2792-2795.

A Pd-catalyzed aerobic oxidation of o-aminophenols and isocyanides gives 2-aminobenzoxazoles and 3-aminobenzoxazines in good yields and a broad substrate scope. This methodology has the advantages of experimental simplicity, mild reaction conditions, and easily accessible starting materials. Furthermore, the synthesis of other types of useful nitrogen heterocycles has been achieved.
B. Liu, M. Yin, H. Gao, W. Wu, H. Jiang, J. Org. Chem., 2013, 78, 3009-3020.

Visible light efficiently mediates a mild intramolecular oxidative cyclization of o-hydroxy-N-aryl-N,N-dialkylformamidines leading to 2-aminobenzoxazole derivatives in excellent yields in the presence of only 1 mol% tris(2,2′-bipyridine)ruthenium(II) as a photoredox catalyst and air as terminal oxidant.
V. P. Srivastava, L. D. S. Yadav, Synlett, 2013, 24, 2758-2762.

Highly efficient conditions for the preparation of 3,3-disubstituted oxindoles by a formal C-H, Ar-H coupling of anilides have been identified using catalytic Cu(OAc)₂•H₂O with atmospheric oxygen as the reoxidant in mesitylene or toluene as solvent; no additional base is required.
J. E. M. N. Klein, A. Perry, D. S. Pugh, R. J. K. Taylor, Org. Lett., 2010, 12, 3446-3449.

3-Alkyl-3-hydroxyoxindoles have antioxidant, neuroprotective, anticancer, and anti-HIV activities. α-Alkylation-α-hydroxylation of oxindoles with benzyl alcohols enables an economical synthesis without using any transition-metal catalysts in very good yields.
S. Wu. W. Song, R. Zhu, J. Hu, L. Zhao, Z. Li, X. Yu, C. Xia, J. Zhao, J. Org. Chem., 2022, 87, 5464-5471.

A heterogeneous copper(II)-catalyzed oxidative cyclization of 2-pyridine ketone hydrazones was achieved in ethyl acetate at room temperature in the presence of an MCM-41-anchored bidentate 2-aminoethylamino copper(II) catalyst and air as the oxidant to provide various [1,2,3]triazolo[1,5-a]pyridines in good yields. The catalyst can be recovered by filtration and reused at least seven times.
G. Jiang, Y. Lin, M. Cai, H. Zhao, Synthesis, 2019, 51, 4487-4497.

Molecular iodine catalyses a benzylic sp³ C-H bond amination of 2-aminobenzaldehydes and 2-aminobenzophenones with benzylamines to provide quinazolines in very good yields. The use of oxygen as an oxidant combined with the transition-metal-, additive- and solvent-free conditions makes the methodology green and economical. 2-Aminobenzyl alcohols could also used as starting materials.
D. S. Deshmukh, B. M. Bhanage, Synlett, 2018, 29, 979-985.

An aerobic, iodine-catalyzed oxidative C(sp³)-H amination/C-N cleavage of tertiary amines affords a route to a wide range of quinazolines and quinazolinones in good to excellent yields via a domino ring annulation. The method is metal-free, peroxide-free, and operationally simple and represents a new avenue for multiple C-N bond formations.
Y. Yan, Y. Xu, B. Niu, H. Xie, Y. Liu, J. Org. Chem., 2015, 80, 5581-5587.

A domino C-H functionalization of glycine derivatives for the production of a series of quinolines was achieved under catalytic radical cation salt induced conditions. A mechanism is proposed, that includes a peroxyl radical cation, which is generated by the coupling between O₂ and TBPA^+•.
X. Jia, F. Peng, C. Qing, C. Huo, X. Wang, Org. Lett., 2012, 14, 4030-4033.

An efficient CuCl₂-catalyzed coupling of nonfunctionalized tetrahydroisoquinolines with organozinc reagents under aerobic conditions proceeds in high yields under mild reaction conditions and is broadly applicable to a wide range of substrates. The reaction involves an iminium ion intermediate that is formed via a SET process.
T. Wang, M. Schrempp, A. Berndhäuser, O. Schiemann, D. Menche, Org. Lett., 2015, 17, 3982-3985.

A palladium-catalyzed highly regioselective C-H allylation/annulation reaction of N-sulfonyl amides with secondary or tertiary allylic alcohols provides 3,4-dihydroisoquinolones bearing a synthetically valuable vinyl substituent. Commercially available allylic alcohol substrates, water as only by-product, and O₂ as terminal oxidant make the use of this process advantageous.
H. Wu, J. Gui, M. Sun, Y. Ma, J. Yang, Z. Wang, J. Org. Chem., 2023, 88, 3871-3882.

A palladium-catalyzed C(sp²)-H allylation/aminopalladation/β-H elimination/isomerization sequence enables an annulation reaction of N-sulfonyl amides and allylbenzenes to construct isoquinolinones and pyridinones in good yield in the presence of air as the terminal oxidant.
R. Zhong, Y. Xu, M. Sun, Y. Wang, J. Org. Chem., 2021, 86, 5255-5264.

A visible-light-promoted C-H alkylation of nitrogen-containing heteroarenes with C4-alkyl 1,4-dihydropyridines (DHPs) as radical precursors enables an efficient late-stage functionalization at ambient temperatures. A broad scope of heteroarenes, including those bearing electron-donating or electron-withdrawing groups, can be successfully alkylated in good yields.
X. Chen, X. Luo, K. Wang, F. Liang, P. Wang, Synlett, 2021, 32, 733-737.

A highly efficient Cu-catalyzed aza-Michael addition of 2-aminobenzoates to β-substituted α,β-unsaturated ketones followed by cyclization and a mild oxidation reaction enable a straightforward one-pot synthesis of 3-carbonyl-4-quinolone derivatives in very good yields under mild reaction conditions with short reaction times.
S. Kang, S. Park, K.-s. Kim, C. Song, Y. Lee, J. Org. Chem., 2018, 83, 2694-2705.

A copper-catalyzed synthesis of quinazolinones from easily available 2-arylindoles and amines or ammonium provided various quinazolinones in very good yields. This simple and mild reaction tolerates a broad range of functional groups.
Y. Feng, Y. Li, G. Cheng, L. Wang, X. Cui, J. Org. Chem., 2015, 80, 7099-7107.

An efficient visible-light-induced C(sp²)-H/N-H cross-dehydrogenative coupling (CDC)-amination with both primary and secondary aliphatic amines allows the direct formation of 3-aminoquinoxalin-2(1H)-ones. Preliminary mechanistic studies reveal that the reaction proceeds through a radical process.
W. Wei, L. Wang, P. Bao, Y. Shao, H. Yue, D. Yang, X. Yang, X. Zhao, H. Wang, Org. Lett., 2018, 20, 7125-7130.

Readily available o-vinylphenols undergo a formal (5 + 2) cycloaddition to alkynes in the presence of catalytic amounts of [Cp*RhCl₂]₂ and Cu(OAc)₂. The reaction generates highly valuable benzoxepine skeletons in a practical, versatile, and atom-economical manner. Using carbon monoxide instead of an alkyne as reaction partner leads to coumarin products of a formal (5 + 1) cycloaddition.
A. Seoane, N. Casanova, N. Quiñones, J. L. Mascareñas, M. Gulías, J. Am. Chem. Soc., 2014, 136, 650-652.

Molecular iodine catalyzes a metal-free oxidative coupling of 2-aminobenzamides with aryl methyl ketones to yield 2-aryl quinazolin-4(3H)-ones. The selectivity of the reaction strongly depends on the quantity of iodine.
S. Mohammed, R. A. Vishwakarma, S. B. Bharate, J. Org. Chem., 2015, 80, 6915-6921.

An N-heterocyclic carbene (NHC)-catalyzed intramolecular Stetter reaction enables a transition-metal-free and mild cross-dehydrogenative coupling of 2-cinnamoyl benzaldehydes to provide 2-aryl naphthoquinones. The intramolecular Stetter reaction is followed by an aerobic oxidation to reinstall the C-C double bond.
A. Ghosh, A. Patra, S. Mukherjee, A. T. Biju, J. Org. Chem., 2019, 84, 1103-1110.

A highly efficient α alkylation of ketones with primary alcohols by the use of a recyclable palladium catalyst has been demonstrated.
M. S. Kwon, N. Kim, S. H. Seo, I. S. Park, R. K. Cheedrala, J. Park, Angew. Chem., 2005, 117, 7073-7075.

A general and mild protocol of oxygen-promoted Pd(II) catalysis allows a selective cross-couplings of alkenyl- and arylboron compounds with various olefins. Unlike most cross-coupling reactions, this new methodology works well even in the absence of bases, consequently averting undesired homo-couplings.
K. S. Yoo, C. H. Yoon, J. W. Jung, J. Am. Chem. Soc., 2006, 128, 16348-16393.

A mild and efficient Pd(II) catalysis leads to the formation of carbon-carbon bonds between various organoboron compounds and alkenes. The resultant Pd(0) species is reoxidized by molecular oxygen to Pd(II). This protocol promotes the desired Pd(II) catalysis, whereas the competing Pd(0) pathways (Heck or Suzuki) are retarded.
Y. C. Jung, R. K. Mishra, C. H. Yoon, K. W. Jung, Org. Lett., 2003, 5, 2231-2234.

A formal hydrotrifluoromethylation of alkynes is achieved via hydroboration/trifluoromethylation using the inexpensive fluoroform-derived [CuCF₃] reagent. Synthetically useful (E)-alkenyl-CF₃ building blocks and 1,1-bis(trifluoromethyl)-substituted alkenes can be prepared under ambient conditions in one pot/one step from alkynes.
L. He, X. Yang, G. C. Tsui, J. Org. Chem., 2017, 82, 6192-6201.

A Pd-catalyzed oxidative cross-coupling reaction of arylboronic acids with α-diazoesters using molecular oxygen as the reoxidant gives E-α,β-diarylacrylates in good yields and very high E-to-Z selectivity.
Y.-T. Tsoi, Z. Zhou, A. S. C. Chan, W.-Y. Yu, Org. Lett., 2010, 12, 4506-4509.

Terminal alkynes can be directly cross-coupled with alkylzinc reagents in the presence of a Pd catalyst at room temperature with air as the oxidant. CO was found to be critical in gaining high chemical yields and selectivities. Good yields were obtained for a wide range of alkynes and alkylzinc reagents.
M. Chen, X. Zheng, W. Li, J. He, A. Lei, J. Am. Chem. Soc., 2010, 132, 4101-4103.

A facile and environmentally friendly synthetic method for a variety of symmetrical 1,3-diyne derivatives is based on a Pd/C-CuI-catalyzed homocoupling reaction of terminal alkynes. The reaction was efficiently catalyzed by an extremely low loading of Pd/C and CuI in the presence of molecular oxygen as the oxidant without any phosphine ligands and bases.
T. Kurita, M. Abe, T. Maegawa, Y. Monguchi, H. Sajiki, Synlett, 2007, 2521-2524.

Cu(II)-catalyzed aerobic 6-endo-trig cyclizations provide 1,6-dihydropyridazines and pyridazines via the judicious choice of reaction solvent. Whereas 1,6-dihydropyridazines were obtained in good yields with MeCN as the reaction solvent, employment of AcOH directly afforded pyridazines in good yields.
Z. Fan, Z. Pan, L. Huang, J. Cheng, J. Org. Chem., 2019, 84, 4236-4245.

A Pd-catalyzed Wacker-type oxidative cyclization under air allows the construction of 2-methylquinolines in good yields under mild conditions.
Z. Zhang, J. Tang, Z. Wang, Org. Lett., 2008, 10, 173-175.

A direct convergent two-component synthesis of quinolines from α,β-unsaturated ketones and o-aminophenylboronic acid derivatives is regiocomplementary to the traditional Skraup-Doebner-Von Miller synthesis and proceeds under basic rather than strongly acidic conditions.
J. Horn, S. P. Marsden, A. Nelson, D. House, G. G. Weingarten, Org. Lett., 2008, 10, 4117-4120.

An annulation between 2-aminobenzyl alcohols, benzaldehydes, and DMSO provides quinolines. Interestingly, introducing substituent groups to the α-position of sulfoxides resulted in the interchange of the positions between benzaldehydes and sulfoxides in the product quinolines.
T. Yang, Z.-w. Nie, M.-d. Su, H. Li, W.-p. Luo, Q. Liu, C.-C. Guo, J. Org. Chem., 2021, 86, 15232-15241.

An efficient copper-catalyzed cascade reaction of (2-aminophenyl)methanols with aldehydes using the combination of cerium nitrate hexahydrate and ammonium chloride leads to a wide range of 2-substituted quinazolines in good yields. The method tolerates a various functional groups and represents a convenient and practical strategy for synthesis of 2-substituted quinazoline derivatives.
Z. Chen, J. Chen, M. Liu, J. Ding, W. Gao, X. Huang, H. Wu, J. Org. Chem., 2013, 78, 11342-11348.

An efficient method enables a synthesis of 4-amino-2-aryl(alkyl)quinazolines from readily available N-arylamidines and isonitriles via palladium-catalyzed intramolecular aryl C-H amidination by isonitrile insertion.
Y. Wang, H. Wang, J. Peng, Q. Zhu, Org. Lett., 2011, 13, 4596-4599.

Palladium-catalyzed oxidative cyclocarbonylation of 2-vinylphenols enables a direct synthesis of various coumarins in good yields in the presence of low pressures of CO, and air or 1,4- benzoquinone as the oxidant. The reaction conditions are attractive in terms of environmental considerations and operational simplicity.
J. Ferguson, F. Zeng, H. Alper, Org. Lett., 2012, 14, 5602-5605.

Cross-dehydrogenative C-N annulations and dealkylative C-N annulations of 2′-N-aryl/alkylaminoacetophenones and 2′-N,N-dialkylaminoacetophenones respectively in the presence of Cu(OAc)₂·H₂O, NaOAc and air gave isatins in good yields. However, on reaction with CuBr, 2′-N-benzylaminoacetophenones underwent selective oxidation at the benzylic position to provide the corresponding benzamides exclusively.
A. Ilanovan, G. Satish, Org. Lett., 2013, 15, 5726-5729.

An easily prepared recyclable TEMPO derived sulfonic salt catalyst, and mineral acids (NaNO₂ and HCl) enable a selective aerobic oxidation of structurally diverse benzylic sp³ C-H bonds of ethers and alkylarenes to provide synthetically and biologically valued isochromanones and xanthones in good yields.
Z. Zhang, Y. Gao, Y. Liu, J. Li, H. Xie, H. Li, W. Wang, Org. Lett., 2015, 17, 5492-5495.

Ruthenium supported on alumina acts as an efficient heterogeneous catalyst for the oxidation of non-activated as well as activated amines to the corresponding nitriles or imines with 1 atm of dioxygen or air.
K. Yamaguchi, N. Mizuno, Angew. Chem. Int. Ed., 2003, 42, 1480-1483.

In the presence of an easily prepared supported ruthenium hydroxide catalyst, Ru(OH)_x/Al₂O₃, various primary azides including benzylic, allylic, and aliphatic ones could be converted into the corresponding nitriles in good yields. The Ru(OH)_x/Al₂O₃ catalyst could be further employed for synthesis of amides in water from benzylic or aliphatic primary azides.
J. He, K. Yamaguchi, N. Mizuno, J. Org. Chem., 2011, 76, 4552-4553.

RuCl₃-catalyzed oxidative cyanation of tertiary amines with sodium cyanide under molecular oxygen at 60°C gives the corresponding α-aminonitriles in excellent yields. This reaction is clean and should be an environmentally benign and useful process.
S.-I. Murahashi, N. Komiya, H. Terai, T. Nakae, J. Am. Chem. Soc., 2003, 125, 15312-15313.

A green dehydrogenation of hydrazo compounds using basic alumina or KF/alumina under solvent-free conditions afforded azo compounds in good to excellent yields.
M. Mihara, T. Nakai, T. Iwai, T. Ito, T. Mizuno, Synlett, 2007, 2124-2126.

Oxidations of organic substrates such as sulfides, secondary amines, N-hydroxylamines, and tertiary amines with molecular oxygen in the presence of 5-ethyl-3-methyllumiflavinium perchlorate catalyst and hydrazine monohydrate in 2,2,2-trifluoroethanol occur highly efficiently to give the corresponding oxidized compounds in excellent yields.
Y. Imada, H. Iida, S. Ono, S.-I. Murahashi, J. Am. Chem. Soc., 2003, 125, 2868-2869.

A regioselective one-pot synthesis of substituted pyrazoles from N-monosubstituted hydrazones and nitroolefins gives products in good yields. A key nitropyrazolidine intermediate is characterized and a plausible mechanism is proposed.
X. Deng, N. S. Mani, Org. Lett., 2006, 8, 3505-3508.

Two general protocols for the reaction of electron-deficient N-arylhydrazones with nitroolefins allow a regioselective synthesis of 1,3,5-tri- and 1,3,4,5-tetrasubstituted pyrazoles. Studies on the stereochemistry of the key pyrazolidine intermediate suggest a stepwise cycloaddition mechanism.
X. Deng, N. S. Mani, J. Org. Chem., 2008, 73, 2412-2415.

A second-generation, water-soluble cobalt catalyst for the formation of trans-THF products via the Mukaiyama aerobic oxidative cyclization gives superior yields and enables greatly simplified purification compared to the previous catalysts. Quarternization of the amino group of the ligand with MeI allows a simple, neutral water extraction.
C. Palmer, N. A. Morra, A. C. Stevens, B. Bajtos, B. P. Machin, B. L. Pagenkopf, Org. Lett., 2009, 11, 5614-5617.

An asymmetric 1,2-addition of alkyl groups to conjugated cyclic enones gave allylic alcohols with chiral quaternary centers. The resultant allylic alcohols are converted into epoxy alcohols with excellent diastereoselectivities. A semipinacol rearrangement provided α,α-dialkyl-β-hydroxy ketones with all-carbon chiral quaternary centers.
S.-J. Jeon, P. J. Walsh, J. Am. Chem. Soc., 2003, 125, 9544-9545.

Highly enantio- and diastereoselective one-pot procedures for the synthesis of epoxy alcohols involve either asymmetric addition of an alkylzinc reagent to an enal or asymmetric vinylation of an aldehyde with divinylzinc reagents. Exposure of the reaction mixtures to dioxygen and addition of catalytic titanium tetraisopropoxide yields epoxy alcohols with good to excellent yields.
A. E. Lurain, A. Maestri, A. R. Kelli, P. J. Carroll, P. J. Walsh, J. Am. Chem. Soc., 2004, 126, 13608-13609.

A. E. Lurain, A. Maestri, A. R. Kelli, P. J. Carroll, P. J. Walsh, J. Am. Chem. Soc., 2004, 126, 13608-13609.

The oxidation of substituted toluenes by molecular oxygen to the corresponding substituted benzoic acids using Co(C₁₈H₃₅O₂)₂/NH₄Br or Co(OAc)₂/NaBr/AcOH as catalysts in the presence of a radical initiator in non-acidic solvents was investigated.
F. Yang, J. Sun, R. Zheng, W. Qiu, J. Tang, M. He, Tetrahedron, 2004, 60, 1225-1228.

A methyl group at an aromatic nucleus is oxidized directly to the corresponding carboxylic acid in the presence of molecular oxygen and catalytic hydrobromic acid under photoirradiation.
S.-I. Hirashima, A. Itoh, Synthesis, 2006, 1757-1759.

β-Ketoesters can directly be transformed to the corresponding α-hydroxymalonic esters, tartronic esters, with molecular oxygen catalyzed by calcium iodide under visible light irradiation from a fluorescent lamp. This convenient tandem oxidation/rearrangement reduces consumption of energy, time, and solvents.
N. Kanai, H. Nakayama, N. Tada, A. Itoh, Org. Lett., 2010, 12, 1948-1951.

An oxidative coupling method for alkyne difunctionalization under metal-catalyst-free conditions affords various β-ketodithianes in very good yields with high regioselectivities. The reaction provides valuable dithianes with controlled formation of a new C-C bond and a C-O bond via a radical coupling pathway.
J. Lai, L. Tian, X. Huo, Y. Zhang, X. Xie, S. Tang, J. Org. Chem., 2015, 80, 5894-5899.

Pd(OAc)₂ in the presence of a BIAN ligand is an efficient catalyst system for the base-free oxidative Heck reaction that outperforms the currently available catalysts for the more challenging substrates studied. The catalyst system is highly selective, and works at room temperature with dioxygen as the oxidant.

Arylations of electron-rich heteroatom-substituted olefins were performed with electron-rich arylboronic acids via palladium(II) catalysis. This mild protocol, which offers access to functionalized enamides, exploits oxygen gas for reoxidation and a stable 1,10-phenanthroline bidentate ligand to promote the palladium(II) regeneration and to control the regioselectivity.
M. M. S. Andappan, P. Nilsson, H. v. Schenck, M. Larhed, J. Org. Chem., 2004, 69, 5212-5218.

Palladium-catalyzed oxidative Heck coupling reaction of coumarins and arylboronic acids allows a direct synthesis of 4-arylcoumarins in good yields. The reaction also showed tolerance toward functional groups such as hydro, methoxy, diethylamino, nitro, and chloro groups.
Y. Li, Z. Qi, H. Wang, X. Fu, C. Duan, J. Org. Chem., 2012, 77, 2053-2057.

An efficient copper-catalyzed oxidative trifluoromethylation of terminal alkynes and aryl boronic acids in the presence of air is successfully achieved by adding both the substrate and a portion of CF₃TMS slowly using a syringe pump to the reaction mixture.
X. Jiang, L. Chu, F.-L. Qing, J. Org. Chem., 2012, 77, 1251-1257.

The chemoselective ring opening of N-tosyl aziridines with aldehydes catalyzed by an N-heterocyclic carbene gave carboxylates of 1,2-amino alcohols. A plausible mechanism for this reaction is discussed.
Y.-K. Liu, R. Li, L. Yue, B.-J. Li, Y.-C. Chen, Y. Wu, L.-S. Ding, Org. Lett., 2006, 8, 1521-1524.

5-Ethyl-3-methyl-2′,4′:3′,5′-di-O-methylenedioxy-riboflavinium perchlorate, which is readily derived from commercially available vitamin B₂, exhibits high catalytic activity for the oxidation of organic sulfides under an oxygen atmosphere with the assistance of hydrazine hydrate as a reductant. This is an inexpensive, convenient, and environmentally benign method for the selective oxidative transformation of sulfides into sulfoxides.
Y. Imada, I. Tonomura, N. Komiya, T. Naota, Synlett, 2013, 24, 1679-1682.

An efficient CuSO₄-catalyzed S-arylation of thiols with aryl and heteroaryl boronic acids at room temperature is established. A wide variety of thiols and arylboronic acids can be converted in the presence of CuSO₄ as the catalyst, inexpensive 1,10-phen·H₂O as the ligand, oxygen as oxidant, and EtOH as environment-friendly solvent.
H.-J. Xu, Y.-Q. Zhao, T. Feng, Y.-S. Feng, J. Org. Chem., 2012, 77, 2649-2658.

In an environmentally friendly, atom-economical, and step-economical oxidation, thiols are used as a synthon for the preparation of thioamides without the use of exogenous sulfur reagents.
X. Wang, M. Ji, S. Lim, H.-Y. Jang, J. Org. Chem., 2014, 79, 7258-7260.

Unsymmetrical diorgano-monosulfides, selenides, and tellurides can be synthesized by the coupling of dichalcogenides with aryl- or alkylboronic acids using a copper catalyst in air. The present reaction takes advantage of both organochalcogenide groups on the dichalcogenide.
N. Taniguchi, J. Org. Chem., 2007, 72, 1241-1245.

A cross-coupling reaction of arylboronic acids with KSCN salt to yield aryl thiocyanates is catalyzed by copper acetate in the presence of 4-methylpyridine serving both as ligand and base under 0.2 MPa of molecular oxygen. Various arylboronic acids were suitable under the reaction conditions.
N. Sun, H. Zhang, W. Mo, B. Hu, Z. Shen, X. Hu, Synlett, 2013, 24, 1443-1447.

A regio and anti-selective copper-catalyzed 1,2-hydroxysulfenylation of alkenes can be carried out by the use of disulfides and acetic acid. Reoxidation of intermediate sulfides by oxygen enables the use of both organosulfide groups of the disulfides.
N. Taniguchi, J. Org. Chem., 2006, 71, 7874-7876.

Alkenyl sulfones can be stereoselectively synthesized from alkenes or alkynes using sodium sulfinates in the presence of CuI-bpy as catalyst and oxygen. The reaction of alkenes gives (E)-alkenyl sulfones via anti addition of the sulfonyl cation followed by an elimination process. Furthermore, the employment of alkynes produces (E)-β-haloalkenyl sulfones in the presence of potassium halides.
N. Taniguchi, Synlett, 2011, 1308-1312.

Copper-catalyzed hydrosulfonylations of both terminal and internal alkynes can be carried out using sodium sulfinates in air. The procedure affords syn-selectively (E)-alkenyl sulfones in good yields.
N. Taniguchi, Synlett, 2012, 23, 1245-1249.

A convenient and efficient synthesis of thiosulfonates in very good yields from thiols and sodium sulfinates involves iron(III)-catalyzed formation of sulfenyl and sulfonyl radicals in situ under aerobic conditions and their subsequent cross-coupling. The utilization of readily available, nontoxic, and inexpensive iron(III) as a catalyst and atmospheric oxygen as an oxidant makes this process green and sustainable.
T. Keshari, R. Kapoorr, L. D. S. Yadav, Synlett, 2016, 27, 1878-1882.

A copper-catalyzed sulfonylation of disulfides using sodium sulfinates in air formed various sulfur-sulfone bonds efficiently and afforded thiosulfonates in good yields. Selenosulfonates could also be prepared.
N. Taniguchi, J. Org. Chem., 2015, 80, 1764-1765.

Visible light mediates a reaction of N-tosyl-protected sulfoximidoyl chlorides with aryl alkynes in the presence of air and a ruthenium photocatalyst to provide β-keto sulfoximines in good yields. The reaction offers high functional group tolerance.
P. Shi, Y. Tu, C. Wang, D. Ma, C. Bolm, J. Org. Chem., 2022, 87, 3817-3824.

A copper-catalyzed aerobic oxidative/decarboxylative phosphorylation of aryl acrylic acids with P(III)-nucleophiles via the Michaelis-Arbuzov rearrangement provides β-ketophosphine oxides, β-ketophosphinates, and β-ketophosphonates in very good yields. The present reaction could be conducted effectively without the use of a ligand and a base.
B. Xiong, L. Si, L. Zhu, Y. Liu, W. Xu, K.-W. Tang, S.-F. Yin, P.-C. Qian, W.-Y. Wong, J. Org. Chem., 2023, 88, 12502-12518.

An oxidation of imidazolinium, imidazolium and benzimidazolium derivatives in the presence of copper and air provides imidazolidinones, imidazolones, and benzimidazolones in good yields under mild conditions. Low yields were obtained with sterically hindered substrates.
D. Li, T. Ollevier, Org. Lett., 2019, 21, 3572-3575.

A silver oxide catalyzed [3 + 2] annulation of nitrones with isocyanides provides a variety of 2,3,4-trisubstituted 1,2,4-oxadiazolidin-5-one derivatives as single diastereomers in very good yields in the presence of oxygen as the terminal oxidant.
X. Shen, A. Shatskiy, Y. Chen, M. D. Kärkäs, X.-S. Wang, J.-Q. Liu, J. Org. Chem., 2020, 85, 3560-3567.

A Cu/ABNO-catalyzed aerobic oxidative coupling of diols and a broad range of primary amines provides N-substituted pyrroles. The reaction proceeds at room temperature with an O₂ balloon as the oxidant using commercially available materials as the substrates and catalysts. The catalyst system offers a good tolerance to sensitive functional groups.
W. Fu, L. Zhu, S. Tan, Z. Zhao, X. Yu, L. Wang, J. Org. Chem., 2022, 87, 13389-13395.

Choice of the reaction medium, either neutral or acidic, enables a photocatalytic chemodivergent synthesis of 2-amino-1,3,4-thiadiazoles and 1,2,4-triazole-3-thiones from isothiocyanates and hydrazones under mild and metal-free conditions.
Q.-H. Teng, F.-L. Lu, K. Wang, L.-Y. Zhou, D.-P. Li, J. Org. Chem., 2023, 88, 7104-7116.

A mild and convenient Cu-catalyzed aerobic oxidative cyclization of β,γ-unsaturated hydrazones provides a broad range of pyrazole derivatives. The reaction is initiated by the formation of a hydrazonyl radical, followed by cyclization and a concomitant C=C bond cleavage.
Z. Fan, J. Feng, Y. Hou, M. Rao, J. Cheng, Org. Lett., 2020, 22, 7981-7985.

A simple skeletal editing protocol "inserts" a nitrogen atom into arylcycloalkenes to form the corresponding N-heterocycles. The use of an inexpensive cobalt catalyst under aqueous and open-air conditions makes this protocol very practical. Examples include late-stage modification of compounds of pharmaceutical interest and complex fused ring compounds.
J. Wang, H. Lu, Y. He, C. Jing, H. Wei, J. Am. Chem. Soc., 2022, 144, 22433-22439.

An efficent cyclization of readily available α,β,γ,δ-unsaturated ketones with ammonium formate under air atmosphere provides asymmetrical 2,6-diarylpyridines. The reaction is metal-free and operationally convenient.
Y. Gao, R. Chen, Y. Ma, Synthesis, 2019, 51, 3875-3882.

Oxidative one-pot sequential reactions of inactivated saturated ketones with electron-deficient enamines enable an efficient synthesis of 3-acylpyridines and pyridine-3-carboxylates. The reaction involve oxidative dehydrogenation of the saturated ketone substrate, followed by [3+3] annulation with β-enaminone or β-enaminoester via a cascade process, including Michael addition, aldol type condensation, and oxidative aromatization.
G. Chen, Z. Wang, X. Zhang, X. Fan, J. Org. Chem., 2017, 82, 11230-11237.

A mild, efficient, and general aromatization of Hantzsch 1,4-dihydropyridines with oxygen was realized at room temperature with 5 mol % of 9-phenyl-10-methylacridinium perchlorate as photocatalyst, which could be easily recovered and reused.
X. Fang, Y.-C. Liu, C. Li, J. Org. Chem., 2007, 72, 8608-8610.

In the presence of activated carbon, Hantzsch 1,4-dihydropyridines and 1,3,5-trisubstituted pyrazolines were aromatized with molecular oxygen to the corresponding pyridines and pyrazoles in excellent yields.
N. Nakamichi, Y. Kawashita, M. Hayashi, Synthesis, 2004, 1015-1020.

An efficient, facile, and eco-friendly synthesis of pyrimidine derivatives involves an oxidative [3 + 2 + 1] three-component annulation of amidines, ketones, and N,N-dimethylaminoethanol as the one carbon source. The reaction tolerates many important functional groups.
Z. Qin, Y. Ma, F. Li, J. Org. Chem., 2021, 86, 13734-13743.

An easy to prepare, tridentate arylazo pincer iron complex catalyzes an eco-friendly construction of trisubstituted pyrimidines under mild aerobic conditions via dehydrogenative functionalization of alcohols with alkynes and amidines.
R. Mondal, G. Chakraborty, A. K. Guin, S. Sarkar, N. D. Paul, J. Org. Chem., 2021, 86, 13186-13197.

A bidentate 2-hydrazinylpyridine directing systems enables a high catalytic reactivity without the need for a high-cost privileged ligand in a cobalt-catalyzed synthesis of isoquinolines via C-H coupling/cyclization with alkynes.
S. Zhou, M. Wang, L. Wang, K. Chen, J. Wang, C. Song, J. Zhu, Org. Lett., 2016, 18, 5632-5635.

CuI-catalyzed coupling of 2-halobenzylamines with β-keto esters or 1,3-diketones in i-PrOH in the presence of of K₂CO₃ produced 1,2-dihydroisoquinolines as the cyclization products, which underwent smooth dehydrogenation under air atmosphere to afford substituted isoquinolines.
B. Wang, B. Lu, Y. Jiang, Y. Zhang, D. Ma, Org. Lett., 2008, 10, 2761-2763.

An intramolecular palladium(II)-catalyzed oxidative carbon-carbon bond formation under air in the presence of pivalic acid as the reaction solvent, instead of acetic acid, results in greater reproducibility, higher yields, and broader substrate scope. The reaction allows the conversion of both electron-rich and electron-deficient diarylamines.
B. Liégault, D. Lee, M. P. Huestis, D. R. Stuart, K. Fagnou, J. Org. Chem., 2008, 73, 5022-5028.

A mild and efficient domino reaction allows a regiospecific synthesis of polysubstituted furans in moderate yields via a copper(I)-catalyzed rearrangement/dehydrogenation oxidation/carbene oxidation sequence of 1,5-enynes in situ formed from alkynols and diethyl but-2-ynedioate.
H. Cao, H. Jiang, W. Yao, X. Liu, Org. Lett., 2009, 11, 1931-1933.

A mild, Pd(OAc)₂-catalyzed regioselective cross-coupling between indoles and potassium aryltrifluoroarylborates gives 2-aryl indoles in moderate yields in the presence of Cu(OAc)₂ in acetic acid at room temperature.
J. Zhao, Y. Zhang, K. Cheng, J. Org. Chem., 2008, 73, 7428-7431.

A metal-free photo-mediated activation of aliphatic alcohols provides differently functionalized benzimidazoles under mild conditions. The interplay of a photocatalyst and a HAT reagent facilitated the activation of aliphatic alcohols. A wide array of diamines with different functional groups were well tolerated.
S. Kumari, A. Joshi, I. Borthakur, S. Kundu, J. Org. Chem., 2023, 88, 11523-11533.

Eosin Y catalyzes a visible-light-mediated C-3 formylation of indole in the presence of tetramethylethylenediamine as a carbon source and air as an oxidant under mild conditions. This protocol tolerates a broad range of functional groups and provides 3-formylated indoles with good yields.
Y. Zhao, H. Li, S. Yin, Y. Wu, G. Ni, Synlett, 2022, 33, 659-663.

Supramolecular nanoassemblies of an AIEE-ICT-active pyrazine derivative (TETPY) with strong absorption in the visible region catalyze the synthesis of a variety of a broad range of benzimidazoles, benzothiazoles and quinazolines in excellent yields under "metal-free" conditions in a mixed aqueous media.
S. Dadwal, M. Kumar, V. Bhalla, J. Org. Chem., 2020, 85, 13906-13919.

In a visible light mediated synthesis of benzothiazoles from 2-aminothiophenol and aldehydes, an in situ-generated disulfide photosensitizes molecular oxygen to generate the key oxidants, singlet oxygen and superoxide anion, for the dehydrogenation step.
H. S. Hwang, S. Lee, S. S. Han, Y. K. Moon, Y. You, E. J. Cho, J. Org. Chem., 2020, 85, 11835-11843.

A copper(II)-catalyzed conversion of bisaryloxime ethers to 2-arylbenzoxazoles involves a cascade C-H functionalization and C-N/C-O bond formation under oxygen atmosphere.
M. M. Guru, M. A. Ali, T. Punniyamurthy, Org. Lett., 2011, 13, 1194-1197.

C-H activation of aryl triazene compounds followed by intramolecular amination in the presence of a catalytic amount of Pd(OAc)₂ provides 1-aryl-1H-benzotriazoles at moderate temperature.
R. K. Kumar, M. A. Ali, T. Punniyamurthy, Org. Lett., 2011, 13, 2102-2105.

A simple and practical benzannulation of maleimides with triethylamine as a 1,3-diene synthon provides phthalimides in good yields under mild conditions. The transformation can be performed in the absence of a metal catalyst with high levels of functional group tolerance.
L. Long, W. Wang, Y. Zhu, W. Luo, Y. Zhang, J. Chen, Y. Wei, Z. Chen, Org. Lett., 2023, 25, 7775-7779.

An efficient oxo-sulfonylation protocol enables the synthesis of N-sulfonylated indazolones from 2H-indazoles employing sulfinic acid as a sulfonylating agent in the presence of tert-butyl hydroperoxide (TBHP) under ambient air. A series of structurally diverse 1-sulfonylindazol-3(2H)-one derivatives were obtained in good yields.
P. Ghosh, S. Mondal, A. Hajra, Org. Lett., 2020, 22, 1086-1090.

A copper-catalyzed one-pot procedure enables the synthesis of imidazo[1,2-a]pyridines with aminopyridines and nitroolefins using air as oxidant. This general reaction appears to be very suitable for the construction of various imidazo[1,2-a]pyridines.
R.-L. Yan, H. Yan, C. Ma, Z.-Y. Ren, X.-A. Gao, G.-S. Huang, Y.-M. Liang, J. Org. Chem., 2012, 77, 2024-2028.

A visible-light-mediated aerobic dehydrogenation reaction enables a simple and environmentally friendly method for synthesizing N-containing heterocycles using a nontoxic, stable, and inexpensive titanium dioxide catalyst and oxygen as green oxidant. The reaction provides a variety of substituted quinolines, indoles, quinoxalines, and 3,4-dihydroisoquinolines.
J. Noh, J.-Y. Cho, M. Park, B. Y. Park, J. Org. Chem., 2023, 88, 10682-10692.

Copper(I) bromide catalyzes a domino reaction of alkyl halides and anthranilamides under air to afford 2-substituted quinazolin-4(3H)-ones in good to excellent yields and with wide functional group tolerance. A mechanism via a four-step domino reaction is proposed.
H. Wei, T. Li, Y. Zhou, L. Zhou, Q. Zeng, Synthesis, 2013, 45, 3349-3354.

The use of arylhydrazines as aryl radical source and air as oxidant enables a transition-metal-free C-3-arylation of quinolin-4-ones in the presence of a base. The reaction proceeds smoothly at room temperature without either prefunctionalization or N-protection of quinoline-4-ones.
M. Ravi, P. Chauhan, R. Kant, S. K. Shukla, P. P. Yadav, J. Org. Chem., 2015, 80, 5369-5376.

A copper-catalyzed tandem reaction of 2-aminobenzamides with tertiary amines provides quinazolinone derivatives. A broad range of substrates reacted under the standard conditions to give the corresponding quinazolinone derivatives in good yields.
W. Xu, X.-R. Zhu, P.-C. Qian, X.-G. Zhang, C.-L. Deng, Synlett, 2016, 27, 2851-2857.

A ruthenium-catalyzed [5 + 1] annulation of 2-alkenylanilines with sulfoxonium ylides provides highly functionalized quinolines with good yields and excellent functional group tolerance.
P. Chen, J. Nan, Y. Hu, Q. Ma, Y. Ma, Org. Lett., 2019, 21, 4812-4815.

A highly atom-efficient PIDA-mediated intramolecular iminoenol tautomer trapping reaction, followed by Et₃N-promoted aerobic oxidative ring construction enables the synthesis of multisubstituted 2-hydroxy-benzo[b][1,4]oxazins from N-(2-hydroxylaryl)enaminones at room temperature under air. O₂ serves as the oxygen source of the hydroxyl group.
H. Zhang, J. Shen, G. Cheng, Y. Feng, X. Cui, Org. Lett., 2018, 20, 664-667.

N. Nakamichi, Y. Kawashita, M. Hayashi, Synthesis, 2004, 1015-1020.

A copper-promoted aerobic oxidative [3+2] cycloaddition of N,N-disubstituted hydrazines with alkynoates provides various substituted pyrazoles in good yields in the presence of a base. In this method, inexpensive Cu₂O serves as the promoter and air acts as the green oxidant. This convenient reaction exhibits high atom, step economy, and regioselectivity.
X. Zou, L. Zheng, X. Zhuo, Y. Zhong, Y. Wu, B. Yang, Q. He, W. Guo, J. Org. Chem., 2023, 88, 2190-2206.

A copper-catalyzed reaction under an atmosphere of air provides 1,2,4-triazole derivatives by sequential N-C and N-N bond-forming oxidative coupling reactions. Starting materials and the copper catalyst are readily available and inexpensive. A wide range of functional groups are tolerated.
S. Ueda, H. Nagasawa, J. Am. Chem. Soc., 2009, 131, 15080-15081.

A copper-mediated remarkable domino sequence of cyclization, trifluoromethylation, and detosylation provides 4-(trifluoromethyl)pyrazoles from readily accessible α,β-alkynic tosylhydrazones and commercially available trifluoromethyltrimethylsilane as the CF₃ source. The reaction conditions are mild and convenient with good functional group compatibility, at room temperature in air.
Q. Wang, L. He, K. K. Li, G. C. Tsui, Org. Lett., 2017, 19, 658-661.

A novel and efficient visible-light-induced reaction of easily accessible active methylene ketone derivatives and different thioureas enables a one-pot synthesis of functionalized 2-aminothiazoles at room temperature. The mild reaction conditions, green chemistry, straightforward work-up, and high yields of the products make this procedure useful for the construction of 2-aminothiazole derivatives.
. Zheng, X. Hu, H. Jiang, H. Guo, L. Wang, Synlett, 2023, 34, 2091-2098.

Sodium carbonate promotes a facile synthesis of 5-amino-1,2,4-thiadiazoles and 5-amino-1,2,4-selenadiazoles in good yields with elemental sulfur and selenium in the presence of air as the green oxidant. The reaction offers low cost, low toxicity, and stable sulfur and selenium sources, water as the sole byproduct, simple operation, and a broad substrate scope.
J.-X. Lin, G.-H. Liu, L.-Q. Liu, Y.-C. Wang, Y. He, J. Org. Chem., 2024, 89, 101-110.

Iridium-catalyzed tandem dehydrogenation of N-heterocycles and alcohols enables regio-selective C-H and N-H bond functionalizations of indolines to provide a diverse range of N- and C3-alkylated indolines/indoles. The practical applicability of this methodology was demonstrated by the preparative-scale synthesis and synthesis of a psychoactive drug, N,N-dimethyltryptamine.
M. Maji, I. Borthakur, S. Srivastava, S. Kundu, J. Org. Chem., 2022, 87, 5603-5616.

L-proline catalyzes a reaction between α,β-unsaturated aldehydes and maleimides to provide biologically and pharmaceutically important phthalimides. The reaction involves an efficient benzannulation that proceeds via a formal [4 + 2] cycloaddition of azadiene intermediates generated in situ from enals and N-substituted maleimides.
M. S. Akhthar, Y. R. Lee, J. Org. Chem., 2020, 85, 15129-15138.

A catalyst and additive-free annulation of 2-pyridylacetates and ynals provides 3-acylated indolizines in very good yields under molecular oxygen. This approach tolerates a wide range of functional groups.
Z. Chen, P. Liang, X. Ma, H. Luo, G. Xu, T. Liu, X. Wen, J. Zheng, H. Ye, J. Org. Chem., 2019, 84, 1630-1639.

S. Ueda, H. Nagasawa, J. Am. Chem. Soc., 2009, 131, 15080-15081.

A convenient, copper-catalyzed C-H and C-N bond activation enables an efficient and conceptually new method for oxidative amination of azoles with tertiary amines. This protocol can be performed in the absence of external base and only requires atmospheric oxygen as oxidant.
S. Guo, B. Qian, C. Xia, H. Huang, Org. Lett., 2011, 13, 522-525.

A cascade reaction enables a regiospecific synthesis of substituted 3-hydroxyisoindolinones under transition-metal-free conditions via base-mediated C-C bond coupling and N-α-sp³C-H bond hydroxylation. The procedure offers high regioselectivity, efficiency, and environmental friendliness. Various substituted 3-hydroxyisoindolinones, including some bioactive molecules, were provided in very good yields.
J. Shen, Q. You, Q. Fu, C. Kuai, H. Huang, L. Zhao, Z. Zhuang, Org. Lett., 2017, 19, 5170-5173.

A metal-free photoredox catalyzed amidyl N-centered radical addition to the C-C triple bond of o-alkynylated benzamides provides isoquinoline-1,3,4(2H)-triones, 3-hydroxyisoindolin-1-ones, and phthalimides via a proton-coupled electron transfer (PCET) process under mild reaction conditions.
M. B. Reddy, K. Prasanth, R. Anandhan, Org. Lett., 2022, 24, 3674-3679.

An iron-catalyzed efficient C-H amination for the construction of imidazole-fused-ring systems can be conducted in anisole as green solvent with water as the only byproduct. The reaction provides Imidazo[1,5-a]pyridines, imidazo[5,1-b]oxazoles, imidazo[5,1-b]thiazoles, imidazo[1,5-a]pyrazines, and imidazo[1,5-a]imidazoles.
J. Peng, S. Li, J. Huang, Q. Meng, L. Wang, W. Xin, W. Li, W. Zhou, L. Zhang, J. Org. Chem., 2023, 88, 16581-16588.

Under visible-light irradiation at room temperature, 2-((aryl/alkyl/H)ethynyl))aryltriazenes reacted with arylsulfinic acids to afford 3-functionalized 2H-indazoles without extra photocatalyst via an electron donor-acceptor complex. In the presence of arylsulfinic acid, 2-(ethynyl)aryltriazenes underwent an intramolecular oxidation/cyclization to provide 2H-indazole-3-carbaldehydes at 50 °C in air.
G. Zhang, Y. Zhang, P. Li, C. Zhou, M. Wang, L. Wang, J. Org. Chem., 2023, 88, 12341-12356.

A metal-free photocatalytic selective hydroxylation of benzylic methylenes to secondary alcohols utilizes low-cost eosin Y as photocatalyst, O₂ as green oxidant, and inexpensive triethylamine as inhibitor for overoxidation. The mild reaction conditions enable the production of secondary benzylic alcohols in good yields.
Z. Tan, T. Chen, J. Zhu, W. Luo, D. Yu, W. Guo, J. Org. Chem., 2024, 89, 2656-2664.

A N-heterocyclic carbene (NHC)-catalyzed synthesis of N-substituted isoindolinone acetates proceeds through a tandem imine umpolung-intramolecular aza-Michael addition followed by oxidation with molecular oxygen in air as the sole oxidant. This method offers atom efficiency, operational simplicity, large-scale syntheses, and mild reaction conditions.
J. Ramarao, P. C. Behera, M. S. Reddy, S. Suresh, J. Org. Chem., 2024, 89, 414-424.

A broad range of flavanones were synthesized in very good yields via a palladium-catalyzed dehydrogenation of chromanones followed by arylation with arylboronic acids. This reaction provides a route to interesting natural products such as naringenin trimethyl ether.
H.-S. Yoo, S.-H. Son, Y. Y. Cho, S. J. Lee, H. J. Jang, Y. M. Kim, D. H. Kim, N. Y. Kim, B. Y. Park, Y. S. Lee, N.-J. Kim, J. Org. Chem., 2019, 84, 10012-10023.

A palladium-catalyzed [4+2] annulation of aryl and alkenyl carboxamides with 1,3-dienes provides 3,4-dihydroisoquinolones and 5,6-dihydropyridinones in very good yields in the presence of air as the terminal oxidant. The method demonstrates good functional group tolerance.
M. Sun, J. Li, W. Chen, H. Wu, J. Yang, Z. Wang, Synthesis, 2020, 52, 1253-1265.

A palladium-catalyzed tandem dehydrogenative [4 + 2] annulation of terminal olefins with N-sulfonyl amides provides important heterocyclic compounds bearing a vinyl substituent with high E stereoselectivity in the presence of air as the terminal oxidant.
M. Sun, W. Chen, X. Xia, G. Shen, Y. Ma, J. Yang, H. Ding, Z. Wang, Org. Lett., 2020, 22, 3229-3233.

Visible light mediates a metal-free oxygenation of quinoxalin-2(1H)-one to quinoxaline-2,3-diones in very good yields by employing Mes-Acr-MeClO₄ as a photocatalyst without using any additive or cocatalyst. O₂ serves as the eco-friendly and green oxidant source for this conversion. In addition, this sustainable approach tolerates a broad range of functional groups.
S. Sau, P. Mal, J. Org. Chem., 2022, 87, 14565-14579.

A visible-light-promoted oxidation of quinoxalin-2(1H)-ones provides various quinoxalinediones in very good yields under an ambient air atmosphere using recyclable graphitic carbon nitride (g-C₃N₄) as a heterogeneous photocatalyst. Importantly, the heterogeneous catalyst can be used at least six times without significant loss of activity.
L.-Y. Xie, Q.-X. Xie, Y.-D. Chen, J.-Y. Zhou, S. Peng, Synthesis, 2023, 55, 443-450.

The use of transition-metal catalysts and TEMPO enables an efficient synthesis of 2-phenyl-4H-chromen-4-one, 2-phenylquinolin-4(1H)-one, and 11H-benzofuro[3,2-b]chromen-11-one derivatives in good yields from 2'-hydroxychalcones, 2'-aminochalcones, and 3-hydroxyflavones, respectively. The methods offer high atom-economy, use of benign solvent and auxiliaries, and easy handling.
A. Singh, S. Singh, K. Ghosh, N. Ahmed, Synthesis, 2023, 55, 4191-4203.

The combination of a cobalt catalyst and oxygen as a terminal oxidant mediates an annulation of terminal alkynes and o-phenylenediamines. This method shows wide substrate scope and good functional group tolerance and provides a wide range of quinoxalines in good yields.
H.-R. Yang, Z.-Y. Hu, X.-C. Li, L. Wu, X.-X. Guo, Org. Lett., 2022, 24, 8392-8396.

FeCl₃-catalyzed decyanation of α-aminonitriles followed by [4 + 2] annulation with terminal alkynes provide a broad range of 2,4-diaryl quinolines in good yields via a Povarov-type [4 + 2] annulation from in situ generated iminium species. The synthetic application of this strategy includes gram-scale synthesis and a continuous-flow process for shorter reaction time.
S. Sathyendran, K. Muthu, K. Govindan, N.-Q. Chen, W.-Y. Lin, G. C. Senadi, Org. Lett., 2023, 25, 4086-4091.

A Cu-catalyzed tandem C-N and C-C bond-formation reaction of aryl boronic acid (or pinacolate ester) with nitriles provides 2-substituted-4-(1H)-quinolones. This environmentally friendly one-step method uses a cheap Cu-catalyst and O₂ (air) as a green oxidant.
S. Tummanapalli, K. C. Gulipalli, S. Bodige, A. K. Pommidi, R. Boya, S. Choppadandi, M. R. Bakangari, S. K. Punna, S. Medaboina, D. Y. Mamindla, A. Kanuka, S. Endoori, V. K. Ganapathi, S. Dharmavaram k., D. Kalbhor, M. Valluri, J. Org. Chem., 2024, 89, 1609-1617.

A Cu/Ag-catalyzed annulation of 3-aryl-2H-azirines with anthranils provides (quinazolin-2-yl)methanone derivatives. The copper-catalyzed cleavage of both the N-C² azirine bond and the N-O anthranil bond is followed by a 1,3-hydroxyl migration and a β-N elimination.
Y. Sun, H. Sun, Y. Wang, F. Xie, Org. Lett., 2020, 22, 6756-6759.

An aerobic dehydrogenative aromatization strategy enables an atom and step economic synthesis of 4-aminoquinolines. Unlike the well-known palladium-catalyzed dehydrogenative aromatization of cyclohexanones with amines, synergistic Pd/Cu catalysis is crucial for 2,3-dihydroquinolin-4(1H)-one type of substrates to give the corresponding 4-aminoquinoline products in good yields.
F. Chen, H. Geng, C. Li, J. Wang, B. Guo, L. Tang, Y.-Y. Yang, J. Org. Chem., 2023, 88, 15589-15596.

An efficient Cu(I)/DMAP/air system enables a one-pot synthesis of 4-oxo-4H-cinnolin-2-ium-1-ides from substituted 2-alkynylanilines and nitrosoarenes. The use of an inexpensive copper catalyst and molecular oxygen as the oxygen source and the oxidant make this an attractive green protocol.
X. Fang, J. Cao, W. Ding, H. Jin, X. Yu, S. Wang, Org. Lett., 2021, 23, 1228-1233.

The iridium-catalyzed dehydrogenative cyclization of 2-aminobiphenyls proceeds smoothly in the presence of a copper cocatalyst under air as a terminal oxidant to yield N-H carbazoles. A similar catalytic system can also be used for a dimerization reaction of 2-aminobiphenyl involving 2-fold C-H/N-H couplings.
C. Suzuki, K. Hirano, T. Satoh, M. Miura, Org. Lett., 2015, 17, 1597-1600.

Treatment of chlorobis(methyldiphenylsilyl)methyllithium with various Grignard reagents and CuCN·2LiCl afforded 1,1-disilylalkylcopper species. Subsequent aerobic oxidation provided various acylsilanes in good yields. The preparation of 1-cyano-1-silylalkylcopper species via consecutive double 1,2-migration of alkyl and cyano groups is described.
J. Kondo, A. Inoue, Y. Ito, H. Shinokubo, K. Oshima, Tetrahedron, 2005, 61, 3361-3369.

Copper-catalyzed aerobic oxidative coupling of terminal alkynes with H-phosphonates affords alkynylphosphonates in high yields.
Y. Gao, G. Wang, L. Chen, P. Xu, Y. Zhao, Y. Zhou, L.-B. Han, J. Am. Chem. Soc., 2009, 131, 7956-7957.

A [Cu(OH)•TMEDA]₂Cl₂ catalyzed tandem reaction allows the synthesis of a series of sterically and electronically divergent phenacyl tertiary phosphine-boranes.
G. Kumaraswamy, G. V. Rao, A. N. Murthy, B. Sridhar, Synlett, 2009, 1180-1184.

A series of propargylic amides were transformed to the corresponding alkylideneoxazolines by a gold(I) catalyst. A subsequent autoxidation to hydroperoxides bearing the heteroaromatic oxazoles followed by reduction to the corresponding alcohols with sodium borohydride enables a highly efficient, and atom-economic access to a series of functionalized 2,5-disubstituted oxazoles.
A. S. K. Hashmi, M. C. B. Jaimes, A. M. Schuster, F. Rominger, J. Org. Chem., 2012, 77, 6394-6408.

A facile copper-catalyzed sustainable thiolation of ketones with sulfonohydrazides provides benzylic thioethers in excellent yield under mild reaction conditions. This approach avoids the use of thiols. The commercial availability of the base and reagents, broad substrate scope, and convenient reaction procedure make the method attractive for benzylic thioether synthesis.
A. R. Jadhao, S. S. Gaikwad, J. Org. Chem., 2023, 88, 14078-14087.

An efficient copper-TBAF-catalyzed arylation of sulfoximines with arylsiloxanes in dichloromethane at room temperature affords the desired N-aryl sulfoximines in good to excellent yields under an oxygen atmosphere. This mild C-N bond formation complements the existing approaches due to the advantageous properties of arylsiloxanes such as availability, low toxicity, ease of handling, high stability, and environmental benignity.
J. Kim, J. Ok, S. Kim, W. Choi, P. H. Lee, Org. Lett., 2014, 16, 4602-4603.

A simple and efficient method for the preparation of thiophosphates from benzenethiols involves copper(I) iodide catalyzed coupling of thiols with H-phosphonates in the presence of triethylamine. The reaction proceeds effectively via an aerobic dehydrogenative coupling to afford the corresponding thiophosphates in good yields.
B. Kaboudin, Y. Abedi, J.-Y. Kato, T. Yokomatsu, Synthesis, 2013, 45, 2323-2327.

Tetrabutylammonium iodide (TBAI) catalyzes an aerobic oxidative cross-dehydrogenative coupling (CDC) of sulfonyl hydrazides with secondary phosphine oxides in the presence of atmospheric oxygen. This metal-free, efficient and practical approach provides an array of diverse phosphinothioates in very good yields.
T. Liu, Y. Zhang, R. Yu, J. Liu, F. Cheng, Synthesis, 2020, 52, 253-262.

A visible-light photocatalytic aerobic oxidative lactonization of arene C(sp²)-H bonds provides benzocoumarin derivatives in good yields in the presence of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and tert-butyl nitrite. This atom economic method offers mild reaction conditions, use of a green oxidant and metal-free catalysis.
Y. Wang, S. Wang, B. Chen, M. Li, X. Hu, B. Hu, L. Jin, N. Sun, Z. Shen, Synlett, 2020, 31, 261-266.

An all-inorganic biomimetic system bearing robust nitrogen-neighbored single-cobalt site/pyridinic-N site (Co-N₄/Py-N) pairs can act cooperatively as an oxidase mimic. The catalyst enables scalable synthesis of O-silylated compounds including silanols, borasiloxanes, and silyl ethers via an unprecedented aerobic oxidation of hydrosilane.
Q. Zhang, M. Peng, Z. Gao, W. Guo, Z. Sun, Y. Zhao, W. Zhou, M. Wang, B. Mei, X.-L. Du, Z. Jiang, W. Sun, C. Liu, Y. Zhu, Y.-M. Liu, H.-Y. He, Z. H. Li, D. Ma, Y. Cao, J. Am. Chem. Soc., 2023, 145, 4166-4176.