Photochemical syntheses. III. The synthesis and photo-isomerization of 1,2-Diphenyl-2a,8b-dihydrocyclobuta[a]naphthalene and some derivatives

Abstract

Fourteen derivatives of the naphthalene-diphenylacetylene photo-adduct (1a) have been thermally isomerized to give high yields of derivatives of 1,2-diphenyl-2a,8b-dihydrocyclobuta[a]naphthalene (1b). Of these only the 4-methoxy derivative (13b) could be rearranged to the isomeric benzocyclooctatetraene (13c). Five alkyl and one methoxy derivative of (1b) were quantitatively isomerized to derivatives of (1a) but the isomerization of the esters (10b) and (11b) gave mixtures. Photo-iso- merization of the methoxybenzocyclooctatetraene (13c) gave exclusively (13b) and (13a).     Mechanistic aspects of these reactions are discussed.