Photochemistry of ω-( o-vinylphenyl)-ω′-(phenyl/2-furyl) butadienes: New approach to 4-substituted benzobicyclo[3.2.1]octadienes

Abstract

Novel 1-( o-vinylphenyl)-4-(phenyl/2-furyl) butadienes ( 4a, b), synthesized in one step, undergo intramolecular photocycloaddition reaction to benzobicyclo[3.2.1]octadiene derivatives ( 6a, b) in very good yield (70–90%). In the case of phenyl derivative ( 4a) only endo-phenyl-benzobicyclo[3.2.1]octadiene isomer ( endo- 6a) was isolated whereas the furan ( 4b) derivative resulted in a mixture of endo- and exo-bicyclic isomer ( 6b). Phenyl benzobicyclo[3.2.1]octadiene derivative ( endo- 6a) underwent further di-π-methane rearrangement leading to tricyclic structure ( endo- 7a). The isolated compound 6a and the product of the rearrangement endo- 7a were characterised by X-ray structure analysis.