Photoreaction of homobenzoquinones with amine donors

Abstract

The photoreactions of diphenylhomobenzoquinones la-d bearing 2-bromo and 2-methyl substituents have been investigated in the presence of amine donors. The products of these reactions are much dependent on the substituents and the nature of added amines. Irradiation of 1-bromo substituted diphenylhomobenzoquinone 1a with triethylamine (TEA) resulted in ring-opening of the fused-cyclopropane moiety to give 2-diphenylmethyl-l,4-benzoquinone 3a. However, the photoreaction of la with N,N-dimethylaniline (DMA) yielded the 1:1 aminated bicyclic dione 4a and bis(p-dimethylamino-phenyl)methane 7 along with 3a. In contrast, irradiation of 1-methyl substituted diphenylhomobenzo-quinones lb-d with TEA brought about hydrogenation of the CC double bond to give the bicyclic diones 8b-d. Similar photoreaction of lb,c with DMA provided only the 1:1 aminated bicyclic diones 4b,c, although the trimethyl substituted 1d remained essentially intact.