New Polycyclic Compounds from Photochemical Rearrangements of Some Substituted 2-Azatricyclo[5.2.2.01,5]undeca-4,8,10-trien-3-ones

The products formed on UV irradiation of several tricyclic compounds (i.e. 3 , 6 , 8 , 15 , and 17 , Schemes 2-4) were studied in detail. A marked dependence of the reaction course on the type and site of substitution was found. Among the several light-induced transformations, a novel rearrangement, i.e. 11 to 9 (Scheme 3) was identified. The formation of the polycyclic compound 13 on irradiation of 8a (Scheme 3) resulted from an unexpected skeletal rearrangement with dearomatization of one benzene ring. The structures of compounds 10 , 11 , and 13 were established by X-ray crystallography (Figs. 1-3). An attempt was made to give a general mechanistic picture of all observed photochemical results (Schemes 4-6).