Oxygen

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Recent Literature

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.

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.

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.

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.

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.

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.

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.

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 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 are 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.

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.

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 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 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.

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.

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.

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.

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.

Y. Imada, H. Iida, S. Ono, S.-I. Murahashi, J. Am. Chem. Soc., 2003, 125, 2868-2869.

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 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.

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.

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 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.

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

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.

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.

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.