Photochemical reactions of 1,4-dicyanonaphthalene with allylic silanes: control of reaction modes by use of solvent and additive effects

Abstract

Solvent and additive effects on the photoreaction of 1,4-dicyanonaphthalene, (1,4-DCN) with allylic silanes ( 1a–c) have been investigated. Irradiation of acetonitrile solutions containing 1,4-DCN and 1a–c in the presence of NaOMe selectively afforded the substitution products 1-(2′-alkenyl)-4-cyanonaphthalenes ( 2a–c) in high yields. The photoreaction of1,4-DCN with 1a–c in the presence of pyrene in CH 3CN-MeOH (4:1) selectively afforded the addition products 1-(2′-alkenyl)-1,4-dicyano-1,2-dihydronaphthalenes ( 3a–c, 3c′) in high yields. The photoreaction of 1,4-DCN with 1a-c in the presence of phenanthrene in CH 3CN-MeOH (4:1) afforded the tricyclic compounds 3,6-dicyano-4,5-benzotricyclo-[4.2.1.0 3,8]-4-nonenes ( 4a–c, 4c′) and 5b (the regioisomer of 4b), which were produced via an intra-molecular (3π+2π) photocycloaddition of 3a–c and 2c′. The mechanistic features of these photoreaction are discussed.