Oxidation of alkoxyphenols. Part XII. The oxidation products of some polymethoxyphenols, and the mechanism of demethylation in neutral solution

Abstract

Oxidation of 2,4-dimethoxyphenol by silver oxide gives methoxy-1,4-benzoquinone and 2-(2,4-dimethoxyphenoxy)-6-methoxy-1,4-benzoquinone. This demethylation apparently involves the decomposition of intermediate aryloxydienones. Isolation of the unstable 4-methoxy-4-(4-methoxy-2,5-di-t-butylphenoxy) 2,5-di-t-butylcyclohexa-2,5-dien-1-one in the oxidation of 4-methoxy-2,5-di-t-butylphenol provides evidence for this mechanism. 2,4,5- and 2,4,6-Trimethoxyphenol are also demethylated under these conditions. Oxidation of 3,4-dimethoxyphenol by ferricyanide provides another example of a dipheno-2,2′-quinone, namely 4,4′,5,5′-tetramethoxydipheno-2,2′-quinone. Depending upon the solvent, oxidation of 2,5-dimethoxyphenol gives either 4,4′-dihydroxy-2,2′,5,5′-tetramethoxybiphenyl or a red polymer, for which a tentative structure is suggested.