The decarboxylation of some α-ethoxycarbonyloxybenzyl cyanides. Part 2. 1,2-Dicyano-1,2-bis(3,4-dimethoxyphenyl)ethane, a minor product formed from 3,4-dimethoxy-α-ethoxycarbonyloxybenzyl cyanide by a free-radical process

Abstract

3,4-Dimethoxy-α-ethoxycarbonyloxybenzyl cyanide was heated in boiling toluene with chloroacetic acid or phosphoryl chloride and gave 1,2-dicyano-1,2-bis (3,4-dimethoxyphenyl) ethane in 2–3% yield; two interconvertible stereoisomers have been isolated. Formation of this substance requires electron transfer to two carbocations to yield a pair of free radicals. The same 1,2-dicyano-1,2-diarylethane was formed in 70% yield by reaction of 3,4-dimethoxyphenylacetonitrile with di-t-butyl peroxide in refluxing t-butylbenzene. The (E)- and (Z)-isomers of the corresponding stilbene have been characterised. Decomposition of the nitrilo-ester with concentrated sulphuric acid gave a trace of 9,10-dicyano-2,3,6,7-tetramethoxyanthracene.