An efficient transformation of substituted N-acyl-#alpha#-dehydro(1-naphthyl) alanines into 1,2-dihydrobenzo[f] quinolinone derivatives via photoinduced intramolecular electron transfer

摘要

The irradiation of substituted (Z)-N-acyl-#alpha#-dehydro (1-naphthyl) alanines (1) having the dialkylamino donor on the carboxamide side chain in methanol was found to give 1,2-dihydrobenzo[f] quinolinone derivatives (2) in good yields, which were formed via the electron-transfer reaction in the excited-state (E)-isomers, while intramolecular photocyclization reactions in the (Z)- and (E)-isomers afforded minor amounts of benzo[f] isoquinolines (3) and 1-azetines (4), respectively. The replacement of the N-acetyl group by the benzoyl (having stronger electron-withdrawing ability and larger steric bulkiness than the former) increased the selectivity for 2 and 4, and this increased selectivity was mainly reflected in a great lowering of that for 3.