Photochemistry of Cis-Fused Bicyclo-2,4-dienes. Ground State Conformational Control

Article abstract of DOI:10.1021/ja00533a026

The photochemistry of a series of simple cis-fused bicyclo<4.n.0>-2,4-dienes (n = 3,4,5) which possess flexible conformations in the ground state has been studied.The bicyclo<4.3.0>nona-2,4-diene system gave rise to cyclic trienes (ring-opened products) and cyclobutenes (ring-closed products) depending upon the wavelength of the excitation light and upon the temperature of the reaction.The bicyclo<4.4.0>deca-2,4-diene yielded materials which are viewed as secondary photoproducts; the expected initial photoproducts could not be detected.The bicyclo<5.4.0>undeca-8,10-diene yielded both a triene and cyclobutene as primary photoproducts.No wavelength dependency was observed.The results indicate ground state conformational control of the photoreactions.