Enantioselective intramolecular [2+2] photocycloaddition using phosphoric acid as a chiral template

The enantioselective intramolecular [2 + 2] photocycloaddition of 4-bishomoally-2-quinolone (quinolinone) using phosphoric acid as a chiral template has been developed. Mechanistic studies using several NMR measurement techniques and density functional theory (DFT) calculations indicate that pi-pi interactions between the phenyl ring on phosphoric acid and quinolinone play important roles in the enantioselectivity.