A novel donor of SET reactions, 1,1-bis(trimethylsilylmethyl)-2-phenylcyclopropane (BTCP), was designed to function as a homoallylic 1-phenyl-3-(trimethylsilylmethyl)-3-butenyl radical (5). Thus, non-irradiated reaction of BTCP with DDQ or chloranil gave a six-membered cyclic compound, which corresponds to a Diels-Alder adduct of 3-trimethylsilylmethyl-1,3-butadiene derived from BTCP. The photoinduced electron transfer reaction of BTCP with ketones afforded the C-C coupling products of 5 in high yields.