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Cobalt‐catalyzed Aerobic Oxidation of Eugenol to Vanillin and Vanillic Acid
Author(s) -
Mao Haifang,
Wang Lizhi,
Zhao Feifei,
Wu Jianxin,
Huo Haohua,
Yu Jun
Publication year - 2016
Publication title -
journal of the chinese chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.329
H-Index - 45
eISSN - 2192-6549
pISSN - 0009-4536
DOI - 10.1002/jccs.201500357
Subject(s) - vanillic acid , chemistry , vanillin , eugenol , catalysis , coniferyl alcohol , organic chemistry , combinatorial chemistry , lignin
A novel, simple, one‐step method of synthesizing vanillin and vanillic acid from eugenol has been developed. The method uses ligand‐ and additive‐free Co(OAc) 2 ⋅ 4H 2 O as catalyst and molecular oxygen as oxidant to achieve catalytic process without isomerizing eugenol. Extensive screening efforts were used to optimize eugenol to obtain vanillin and vanillic acid. Under optimal conditions, the reaction provided vanillin and vanillic acid with 68.5 % and 15.2 % yields, respectively. Apart from the desired products, coniferyl alcohol 9‐methyl ether and 4‐hydroxy‐3‐methoxycinnamaldehyde as two intermediates were also detected in the reaction process. Level changes of all compounds over time were presented in the reaction. The reaction pathway from eugenol to vanillic acid was validated by conducting several control experiments. Furthermore, a possible reaction mechanism dominated by a circular redox reaction from Co(III) and Co(II) species was proposed. This method offers a potentially practical alternative for manufacturing vanillin and vanillic acid efficiently.