Photoinduced ene-reaction of 9-methylene-9,10-dihydrophenanthrene with alkenes

Irradiation of 9-methylene-9,10-dihydrophenanthrene () in the presence of 1,1-diphenylethene or styrene in benzene afforded ene-reaction adduct in good yield. In the absence of arylalkenes, the dimerized product of , 9-[2-(9-phenanthryl)ethyl]-9,10-dihydrophenanthrene, and 9-methylphenanthrene were obtained as major products.