ALLYLATION OF QUINONES BY ALLYLIC INDIUM REAGENTS

Allylation of a variety of quinones by allylic indium sesquihalides was studied. Reactions of unsubstituted p-benzoquinone with allylindium, prenylindium, and geranylindium reagents gave, after oxidation with silver oxide, the corresponding allylated quinones in good yields. These reactions appear to proceed via 1,2-addition of the allylic indium reagents at the gamma-carbon followed by [3,3] sigmatropic rearrangement. Substituted quinones reacted with allylindium reagent giving excellent yields of allylquinols, whereas with prenylindium and geranylindium reagents, trisubstituted quinones gave diprenylcyclohexene-1,4-diones and 2,3-disubstituted quinones gave mixtures of prenylhydroquinones and diprenylcyclohexene-1,4-diones. In the prenylation of haloquinones, 1,2-addition, [3,3] sigmatropic rearrangement, and elimination of indium(III) halide occurred in sequence yielding prenylquinones. 2-Hydroxy- and 2-methoxy-1,4-naphthoquinones gave alpha-addition products with prenylindium and cinnamylindium reagents.