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1,4-Benzoquinone, BQ

1,4-Benzoquinone is a dehydrogenation reagent. The derivatives tetrachloro-1,4-benzoquinone and 2,3-dichloro-5,6-dicyanobenzoquinone are stronger oxidants, while duroquinone is a weaker oxidant. Whereas the resulting phenolate as reaction product of 1,4-benzoquinone (hydroquinone) is nucleophilic, a similar oxidant - 3,3',5'5-tetra-tert-butyldiphenoquinone - can be used in the presence of sensitive electrophilic groups.

Recent Literature

In the presence of PdCl2(MeCN)2, 1,4-benzoquinone, and t-BuOH, aryl-substituted olefins can selectively be oxidized to aldehydes. In this efficient and aldehyde-selective Wacker oxidation, very good yield of aldehyde can be obtained, and up to 99% selectivity can be achieved with styrene-related substrates.
P. Teo, Z. K. Wickens, G. Dong, R. H. Grubbs, Org. Lett., 2012, 14, 3237-3239.

A mild oxidation of alkyl enol ethers to enals employs low loadings of a palladium catalyst and tolerates a diverse array of functional groups, while allowing the formation of di-, tri-, and tetrasubtituted olefins. The application of this methodology to intramolecular reactions of alkyl enol ethers containing pendant alcohols provides furan and 2,5-dihydrofuran products.
M. G. Lauer, W. H. Henderson, A. Awad, J. P. Sambuli, Org. Lett., 2012, 14, 6000-6003.

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.

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.

The presence of a base strongly improves the efficiency and the selectivity of the Pd-catalyzed oxidation of terminal alkenes in carboxylic acids. The methodology is particularly well adapted for the oxidation of homoallylic alcohols, for which the resulting acyloxylated products are obtained selectively as E-isomers in good yields.
E. Thiery, C. Aouf, J. Belloy, D. Harakat, J. Le Bras, J. Muzart, J. Org. Chem., 2010, 75, 1771-1774.

The combination of a bidentate-sulfoxide-ligated palladium complex combined and Ag2CO3 catalyzes an allylic C-H acyloxylation of terminal alkenes with 4-nitrobenzoic acid in the presence of 1,4-benzoquinone under mild reaction conditions. Ag2CO3 as an additive and 4-nitrobenzoic acid as a carboxylate source were essential to exhibiting high catalytic activity and regioselectivity.
A. Skhiri, H. Nagae, H. Tsurugi, M. Seki, K. Mashima, Org. Lett., 2021, 23, 7044-7048.

Pd(OAc)2, sulfoxide-oxazoline (sox) as a ligand and benzoquinone as an oxidant enable a ligand-controlled branch-selective allylic C-H carboxylation. The developed catalytic system couples terminal alkenes and carboxylic acids to furnish the corresponding branched allylic esters with high regioselectivity.
H. Kondo, F. Yu, J. Yamaguchi, G. Liu, K. Itami, Org. Lett., 2014, 16, 4212-4215.

In a Pd(II)-catalyzed enantioselective Markovnikov hydrooxygenation of unactivated terminal alkenes using a substituted pyridinyl oxazoline (Pyox) ligand, a (EtO)2MeSiH/BQ redox system is vital for the highly selective and efficient hydrooxygenation. This method provides efficient access to a broad range of optically pure alcohol esters from easily available alkenes with excellent enantioselectivities.
X. Yang, X. Li, P. Chen, G. Liu, J. Am. Chem. Soc., 2022, 144, 7972-7977.

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.

Palladium-catalyzed reductive cross-coupling reaction of various protected allylic amine derivatives with alkylzinc reagents yields anti-Markovnikov products. Preliminary mechanistic studies suggest that a reversible β-hydride elimination/hydride insertion process furnishes the primary Pd-alkyl intermediate, which then undergoes transmetalation followed by reductive elimination.
R. J. DeLuca, M. S. Sigman, J. Am. Chem. Soc., 2011, 133, 11454-11457.

A Pd(PPh3)4-catalyzed reaction between α-diazocarbonyl compounds and arylboronic acids leads to cross-coupled products in good yields.
C. Peng, Y. Wang, J. Wang, J. Am. Chem. Soc., 2008, 130, 1566-1567.

A palladium-catalyzed oxidative borylation reaction of readily available N-tosylhydrazones provides di-, tri-, and tetrasubstituted alkenylboronates. This highly efficient and practical reaction offers mild conditions, broad substrate scope, and good functional group tolerance. One-pot Suzuki coupling and other transformations highlight the synthetic utility of the approach.
Y. Ping, R. Wang, Q. Wang, T. Chang, J. Huo, M. Lei, J. Wang, J. Am. Chem. Soc., 2021, 143, 9769-9780.

A palladium-catalyzed allylic C-H oxidative allylation of sulfoxonium ylides provides conjugated dienones in good yields. This conversion offers mild reaction conditions, wide substrate scope, and excellent regioselectivity.
C. Li, M. Li, W. Zhong, Y. Jin, Y. Jin, J. Li, W. Wu, H. Jiang, Org. Lett., 2019, 21, 872-875.

A palladium-catalyzed oxidative cross-coupling of vinyl boronic acids and cyclic α-diazocarbonyl compounds enables an efficient synthesis of 1,3-diene compounds. Mechanistically, the reaction involves migratory insertion of palladium carbene as the key step.
Y. Xia, Y. Xia, Z. Liu, Y. Zhang, J. Wang, J. Org. Chem., 2014, 79, 7711-7717.

1,4-Benzoquinones have been found to prevent olefin isomerization of a number of allylic ethers and long-chain aliphatic alkenes during ruthenium-catalyzed olefin metathesis reactions. This mild, inexpensive, and effective method increases the overall product yield and purity.
S. H. Hong, D. P. Sander, C. W. Lee, R. H. Grubbs, J. Am. Chem. Soc., 2005, 127, 17160-17161.

A Pd-catalyzed α,β-desaturation of N-protected lactams provides conjugated unsaturated counterparts under mildly acidic conditions at room temperature. The reaction tolerates a wide range of functional groups and shows reactivity complementary to that of prior desaturation methods. Lactams with various ring sizes and substituents at different positions all reacted smoothly.
M. Chen. G. Dong, J. Am. Chem. Soc., 2017, 139, 7757-7760.

A mild oxidation of alkyl enol ethers to enals employs low loadings of a palladium catalyst and tolerates a diverse array of functional groups, while allowing the formation of di-, tri-, and tetrasubtituted olefins. The application of this methodology to intramolecular reactions of alkyl enol ethers containing pendant alcohols provides furan and 2,5-dihydrofuran products.
M. G. Lauer, W. H. Henderson, A. Awad, J. P. Sambuli, Org. Lett., 2012, 14, 6000-6003.

An iridium-catalyzed hydrogen transfer in the presence of p-benzoquinone allows the synthesis of various substituted benzofurans, benzothiophenes, and indoles from substituted benzylic alcohols.
B. Anxionnat, D. G. Pardo, G. Ricci, K. Rossen, J. Cossy, Org. Lett., 2013, 15, 3876-3879.

A regioselective 5-exo-trig intramolecular oxidative cyclization of ortho-cinnamyl phenols using [PdCl2(CH3CN)2] as catalyst and benzoquinone as an oxidant provides functionalized 2-benzyl benzo[b]furans. Further, a one-pot, sequential synthesis of ortho-cinnamyl phenols, starting from readily available alcohols and phenols, followed by Pd-catalyzed oxidative annulation, has also been developed.
M. Rehan, R. Nallagonda, B. G. Das, T. Meena, P. Ghorai, J. Org. Chem., 2017, 82, 3411-3424.

A combination of Pd(II)/bis-sulfoxide C-H activation and Lewis acid co-catalysis enables the synthesis of chroman, isochroman, and pyran motifs from a wide range of alcohols. Mechanistic studies suggest that the reaction proceeds via initial C-H activation followed by a novel inner-sphere functionalization pathway.
S. E. Ammann, G. T. Rice, M. C. White, J. Am. Chem. Soc., 2014, 136, 10834-10837.

A novel chelate-controlled intermolecular oxidative Heck reaction proceeds with a wide range of nonresonance stabilized α-olefin substrates and organoboron reagents to afford internal olefin products in good yields and outstanding regio- and E:Z stereoselectivities. Pd-H isomerization, common in many Heck reactions, is not observed under these mild, oxidative conditions.
J. H. Delcamp, A. P. Brucks, M. C. White, J. Am. Chem. Soc., 2008, 130, 11270-11271.

A Pd-catalyzed intermolecular 1,2-carboamination route to indolines from N-aryl ureas and 1,3-dienes proceeds under mild conditions in relatively nonacidic media via a C-H insertion/carbopalladation/nucleophilic displacement process. The in situ generation, or preformation of a palladium tosylate emerges as a key parameter in gaining the requisite reactivity.
C. E. Houlden, C. D. Bailey, J. G. Ford, M. R. Gagné, G. C. Lloyd-Jones, K. I. Booker-Milburn, J. Am. Chem. Soc., 2008, 130, 10066-10067.

An oxidative Heck reaction enables a selective formation of complex dienes and polyenes from nonactivated terminal olefins and slight excesses of vinyl boronic esters that feature diverse functionality. The reaction proceeds via oxidative Pd(II)/sulfoxide catalysis that retards palladium-hydride isomerizations which previously limited the Heck manifold’s capacity for furnishing stereodefined conjugated dienes.
J.-J. Dai, C. Fang, B. Xiao, J. Yi, J. Xu, Z.-J. Liu, X. Lu, L. Liu, Y. Fu, J. Am. Chem. Soc., 2013, 135, 8436-8439.

A regioselective rhodium(III)-catalyzed oxidative C-H activation/annulation of salicylaldehydes with propargylic acetates provides 3-vinyl chromones in good yields with broad functional group tolerance. 3-Vinyl chromones were converted into biologically active benzo[c]xanthones by I2-mediated oxidative electrocyclization.
B. Li, J. Zhu, X. Zheng, W. Ti, Y. Huang, H. Yao, J. Org. Chem., 2023, 88, 548-558.

Eosin Y catalyzes a visible-light-promoted C2 selective arylation of quinoline and pyridine N-oxides with diaryliodonium tetrafluoroborate as an arylation reagent under mild conditions. This methodology offers high regioselectivity, simple operation and good functional group tolerance.
D. Li, C. Liang, Z. Jiang, J. Zhang, W.-T. Zhuo, F.-Y. Zou, W.-P. Wang, G.-L. Gao, J. Song, J. Org. Chem., 2020, 85, 2733-2742.