Photoinduced electron-transfer reactions: Rearrangements of bicyclopropenyl radical cation.

The reaction of 3,3'-dimethylbicyclopropenyl (1) with photoexcited electron acceptors (chloranil, fluoranil) results in conversion to a 4:1 mixture of o- and m-xylene. Nuclear spin polarization effects observed during irradiation provide direct evidence for the intermediacy of 3,4-dimethylbenzvalene (2).