Anodic oxidation of carboxamides. Part I. Anodic oxidation and pyridination of 4- and 4′-substituted benzanilides

Abstract

Anodic oxidations of several 4- and 4′-substituted benzanilides were investigated by cyclic voltammetry and controlled potential electrolysis at a glassy-carbon electrode in aqueous buffer solution and also in dry acetonitrile in the absence and presence of pyridines. 4′-Methoxybenzanilide (MBA) showed two anodic peaks between pH 9·5 and 11·5, and a single anodic peak at higher and lower pH values. On electrolysis of MBA in weakly acidic or neutral solution, N-benzoyl-p-benzoquinone imine was formed, and on electrolysis in alkaline and strongly acidic solution, p-benzoquinone and benzamide were the main products. Anodic oxidation of MBA in acetonitrile containing excess of pyridine gave the pyridinated MBA, 1-(2-benzamido-5-methoxyphenyl)pyridinium perchlorate.