The chemistry of hydroxyquinones. Part I. The reaction of 2-hydroxybenzoquinones with alkaline hydrogen peroxide

Abstract

The reaction of 2-hydroxybenzoquinones with alkaline hydrogen peroxide involves initial formation of the 5,6-diol. Quinones having no 6-substituent give a product which is subject to rapid oxidation by molecular oxygen to yield an α,β,γ-triketone which suffers a benzylic acid rearrangement at the 6,1-diketo-group and subsequent decarboxylation to form a 4,5-dihydroxycyclopentane-1,3-dione. Under acid conditions the latter is rapidly dehydrated to a cyclopentane-1,2,4-trione containing one less carbon atom than the original quinone.

Quinones containing a 6-methyl group undergo an α-ketol rearrangement at the 6,1-α-ketol group to give a 4-acetyl-4,5-dihydroxycyclopenta-1,3-dione which is stable under alkaline conditions. In acid these products suffer deacetylation and dehydration to give cyclopentane-1,2,4-triones containing two carbon atoms less than the original quinone.