Asymmetric transformation of chiral auxiliary-substituted N-acyl-α-dehydro(1-naphthyl)alanines into 3,4-dihydrobenzo[f]quinolinone derivatives via photoinduced electron transfer

Electron transfer-initiated photocyclizations of the title compounds [] with an (S)-alanine methyl ester auxiliary in methanol containing a tertiary amine were found to give (S,S)- and (R,S)-3,4-dihydrobenzo[f]quinolinones () as major products. The magnitude of diastereomeric excess (de) for was varied from 0 to 55%, depending on the properties of the amine and solvent employed. The mechanism of asymmetric induction in the photocyclization process eventually affording was discussed based on solvent, tertiary amine and temperature effects on the de value.