Photoinduced Electron Transfer Reaction of Mono- and Dicyanonaphthalenes with Allyltrimethylsilane: Synthesis of Benzotricyclo3,8>nonenes by Reductive Photoallylation and Intramolecular (2? + 2?) Photocycloaddition

Article abstract of DOI:10.1016/0040-4020(95)00326-4

Irradiation of an acetonitrile-methanol (4:1) solution containing 1-cyanonaphthalene and allyltrimethylsilane (1) through Pyrex filter (>280 nm) regioselectively gave 3-cyano-4,5-benzotricyclo<4.2.1.0^3,8>-4-nonene.The photoreaction of 2-cyanonaphthalene, 1-cyano-2-methylnaphthalene, 1-cyano-4-methylnaphthalene, 1,5- and 2,3-dicyanonaphthalenes with 1 gave the corresponding benzotricyclic compounds also in a regioselective manner.However, the photorection of 2,3-disubstituted 1,4-dicyanonaphthalenes with 1 gave no benzotricyclic compounds, but only the allyl substitution and reductive allylation products.These photoreactions were initiated by photoinduced electron transfer from 1 to the excited singlet states of mono- and dicyanonaphthalenes.The reductive allylation products from the former cyanonaphthalenes afforded the benzotricyclic compounds by an intramolecular (2? + 2?) photocycloaddition in good yields.The regioselectivity in the allylation reaction is discussed on the basis of the results of MO calculations of the radical anions of mono- and dicyanonaphthalenes.