The photochemistry of 2, 3-diphenyl-1, 4, 5-trimethyl-5-vinylcyclopentadiene and 1, 2- diphenyl-3, 4, 5-trimethyl-5-vinylcyclopentadiene was studied. The triplet of the 2, 3-diphenyl isomer was found to undergo a 1, 5-vinyl migration; in contrast, the 1, 2-diphenyl diene was unreactive. On direct irradiation, in addition to vinyl migration, four photoproducts were formed from the cyclopentadienes. These were shown to be 5, 6-diphenyl-1, 2, 7- ...
