Organic Chemistry Portal >
Reactions > Organic Synthesis Search

Categories: C=O Bond Formation > Synthesis of carboxylic acids >

Synthesis of carboxylic acids by oxidation of benzylic substrates

Recent Literature

Cost-effective and widely applicable protocols for controlled and predictably selective oxidation of methyl-/alkylarenes to corresponding value-added carbonyls have been developed, using a surfactant-based oxodiperoxo molybdenum catalyst in water and hydrogen peroxide (H2O2) as an environmentally benign green oxidant without any external base, additive, or cocatalyst.
P. Thiruvengetam, D. K. Chand, J. Org. Chem., 2022, 87, 4061-4077.

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.

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.

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.

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 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.


Benzyl chlorides and bromides can be directly oxidized to the corresponding benzoic acids in an eco-safer way using 30% hydrogen peroxide with Na2WO4 * 2H2O as a catalyst and [CH3(n-C8H17)3N]+HSO4 as a phase-transfer agent (PTC) without any organic solvents.
M. Shi, Y.-S. Feng, J. Org. Chem., 2001, 66, 3235-3237.

An I2-promoted direct conversion of arylacetic acids into aryl carboxylic acids under metal-free conditions involves decarboxylation followed by an oxidation reaction enabled just by using DMSO as the solvent as well as an oxidant. Notably, aryl carboxylic acids are isolated by simple filtration technique and obtained in good to excellent yields, which makes this protocol applicable for large-scale synthesis.
H. P. Kalmode, K. S. Vadagaonkar, S. L. Shinde, A. C. Chaskar, J. Org. Chem., 2017, 82, 3781-3786.