[reaction: see text] The 9,10-dicyanoanthracene-sensitized photoreaction of 1-methyl- and 1,1'-dimethyl-2,2',3,3'-tetraphenylbicyclopropenyl gives the corresponding benzene and Dewarbenzene derivatives, indicating that their photoinduced electron-transfer bicyclopropenyl-benzene rearrangements proceed via Dewarbenzenes.