Specific photocyclization of 1,4-diarylcyclohepta-1,3-dienes having naphthyl group on 1-or 4-position

The direct photocyclization of four 1,4-diarylcyclohepta-1,3-dienes (1a-d) with different aryl groups (phenyl, 1-naphthyl, and 2-naphthyl groups) by a XeCl excimer laser (308 nm.) in hexane gave 1,5-diarylbicyclo[3.2.0]hept-6 -enes 2a-c). The efficiency of the photochemical cyclization and fluorescen ce quantum yield strongly depended upon the aromatic substituents and this is interpreted by the conformation of the molecules.