Electro-organic reactions. Part I. The cathodic cleavage in methanol solution of benzylic carbon–oxygen and carbon–fluorine bonds

Abstract

Controlled potential electroreduction of methanol solutions of p-methoxycarbonylbenzyl acetate and p-methoxycarbonylbenzyl methyl ether results in cleavage to methyl p-toluate in high yield and with good current efficiency. Substituted benzotrifluorides may similarly be cleaved to the substituted toluene. For efficient reduction an electron-accepting substituent (CO₂Me or CN) is required which must be para to the group undergoing cleavage. The effect of substituents and of added acetic acid on the product distribution, together with voltammetric data, indicate an e.c.e. mechanism. Attempts to effect partial defluorination of the CF₃ group, including the use of a rapidly rotating lead disc electrode, failed.