Synthesis of carboxylic acids by oxidative cleavages and rearrangements
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 mixture of Oxone and trifluoroacetic acid enables a simple and mild metal-free oxidation of various ketones or arylalkynes to the corresponding carboxylic acids in excellent yields.
K. A. A. Kumar, V. Venkateswarlu, R. A. Vishwakarma, S. D. Sawant, Synthesis, 2015, 47, 3161-3168.
A metal-free and one-pot two-step synthesis of aryl carboxylic acids from aryl alkyl ketones has been performed with iodine as the catalyst, DMSO and TBHP as the oxidants. Various aryl alkyl ketones could be converted into their corresponding aryl carboxylic acids in very good yields.
L. Xu, S. Wang, B. Chen, M. Li, X. Hu, B. Hu, L. Jin, N. Sun, Z. Shen, Synlett, 2018, 29, 1505-1509.
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.
A catalytic, asymmetric conjugate addition of carbamates to enoyl systems provides a highly enantioselective two-step access to N-protected β-amino acids.
C. Palomo, M. Oiarbide, R. Halder, M. Kelso, E. Gómez-Bengoa, J. García, J. Am. Chem. Soc., 2004, 126, 9188-9189.
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. Itoh, Synlett, 2011, 2896-2900.
A mild, fast protocol for the conversion of β-ketoesters and β-diketones to carboxylic acids with use of CAN in CH3CN is described. The method is compatible with a number of functional groups, and can generate carboxylic acids under neutral conditions. The mechanism is discussed.
Y. Zhang, J. Jiao, R. A. Flowers, II, J. Org. Chem., 2006, 71, 4516-4520.
A smooth, organocatalytic one-pot oxidative cleavage of terminal 1,2-diols to one-carbon-unit-shorter carboxylic acids is catalyzed by 1-Me-AZADO in the presence of a catalytica amount of NaOCl and NaClO2 under mild conditions. A broad range of substrates including carbohydrates and N-protected amino diols were converted without epimerization.
M. Shibuya, R. Doi, T. Shibuta, S.-i. Uesugi, Y. Iwabuchi, Org. Lett., 2012, 14, 5006-5009.
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.