Oxidative cross-coupling of some 2,6- and N,N-disubstituted aniline derivatives with 4-aminophenol mediated by Cerium(IV) ions in aqueous perchloric acid

摘要

The mechanism of the oxidation of mixtures of 2,6-dimethylaniline (1), N,N-dimethylaniline (2), 2,6-diethylaniline (3), N,N-diethylaniline (4), N-methylaniline (5), 2,6-difluoroaniline (6), and 2,3,5,6-tetrafluoroaniline (7) with 4-aminophenol (8) by cerium(IV) ions in aqueous perchloric acid has been investigated. The indoaniline salts [O=C6H4=N-C6H2(R-1)(2)NH(R-2)(2)]+ClO4- (R-1 = H, R-2 = CH3, C2H5 or vice versa) are formed as intermediates in the cross-coupling reaction; they undergo oxidation to imino-4-benzoquinone (9) and its corresponding derivatives by cerium(IV) ions in high yields. The mechanism of this process is discussed.