Highly selective conversion of N-aroyl-α-dehydronaphthylalaninamides into 3,4-dihydrobenzoquinolinone derivatives via photoinduced intermolecular electron transfer

The irradiation of substituted (Z)-N-aroyl-α-dehydronaphthylalaninamides [] in methanol containing triethylamine (TEA) with Pyrex-filtered light was found to give 3,4-dihydrobenzoquinolinone derivatives () in high yields along with minor amounts of 4,5-dihydrooxazole derivatives (). Analysis of the substituent effects on product composition revealed that both the photoreactivity of and the selectivity of are decreased with increasing electron-withdrawing ability of the substituent introduced at the para-position on the N-benzoyl benzene ring. From the analysis of the dependence of the quantum yield for the formation of on the TEA concentration, it was found that back electron transfer occurs efficiently within an anion radical–TEA cation radical pair intermediate.