Photoreactions of (2-substituted-phenyl)pentamethyldisilanes

Photolysis of (2-allyloxyphenyl)pentamethyldisilane 2a in benzene provides a novel intramolecular photoproduct 5 via silatriene intermediate 3 in addition to 6 and 7 but the photoreaction of [2-(3,3-dimethyl-2-propenyloxy)phenyl]pentamethyldisilane 2b in benzene affords 6 and 12 instead of a expected intramolecular photoproduct.