Enantioselective reduction of azaarene-based ketones via visible light-driven photoredox asymmetric catalysis.

An enantioselective reduction of azaarene-based ketones through photoredox asymmetric catalysis is reported. With a transition metal-free dual catalytic system including a chiral phosphoric acid and a photosensitizer DPZ mediated by visible light, the transformations involved a tandem process involving double single-electron-transfer reductions and enantioselective protonation, providing valuable chiral alcohols in high yields (up to >99%) with good to excellent enantioselectivities (up to 97% ee).