Light-induced and related reactions of quinones. Part VII. Cleavage and isomerisation of some (1-hydroxyalkyl)-1,4-benzoquinones

Abstract

The synthesis is described of 1,4-benzoquinones carrying, severally, the following side-chains: CH(OH)·CH₂Ph,CD(OH)·CH₂Ph, CMe(OH)·CH₂Ph, CH(OH)·CHPh₂, CH(OH)·CH₂·CH:CH₂, and CMe(OH)·CH₂·CH:CH₂. When irradiated with visible light all the secondary alcohols yield 2,5-dihydroxybenzaldehyde, and all the tertiary alcohols give 2,5-dihydroxyacetophenone, probably via fragmentation of the derived alkoxyl radicals. The tertiary alcohols also yield isomers in which reorganisation of the side-chain has occurred. Mechanisms are suggested.