Organocatalytic Enantioselective Protonation for Photoreduction of Activated Ketones and Ketimines Induced by Visible Light

摘要

The first catalytic asymmetric photoreduction of 1,2-diketones and alpha-keto ketimines under visible light irradiation is reported. A transition-metal-free synergistic catalysis platform harnessing dicyanopyrazine-derived chromophore (DPZ) as the photoredox catalyst and a non-covalent chiral organocatalyst is effective for these transformations. With the flexible use of a chiral Bronsted acid or base in H+ transfer interchange to control the elusive enantioselective protonation, a variety of chiral alpha-hydroxy ketones and alpha-amino ketones were obtained with high yields and enantioselectivities.