FORMATION OF ISOQUINOLINE DERIVATIVES BY THE IRRADIATION OF N-ACETYL-#alpha#-DEHYDROPHENYLALANINE ETHYL ESTER AND ITS DERIVATIVES

摘要

The irradiation of a nitrogen-purged acetonitrile solution of the title compounds(1)with Pyrex filtered light was found to give isoquinoline derivatives (2)via the excited state (Z)-isomers,whereas in methanol 1-azetine derivative was also detected along with 2 but side reactions occurred appreciably on prolonged irradiation. An examination of substitunent effects on the reactivities of the excited state(Z)-isomers shows that the efficiency for formation of 2-undergoes great steric and electronic effects of the substituent introduced into the benzene ring of 1,though the bulkiness of the alkoxycarbonyl group in 1 afected this efficiency to only a slight extent.On the other hand,in the presence of benzophenone as a triplet sensitizer,the starting(Z)-isomer underwent an exclusive isomerization into the corresponding (E)-isomer without yielding any isoquinoline derivative,being consistent with the occurrence of the photocyclization reaction from the excited singlet state (Z)-isomer.