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

Abstract The first catalytic asymmetric photoreduction of 1,2‐diketones and α‐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 Brønsted acid or base in H + transfer interchange to control the elusive enantioselective protonation, a variety of chiral α‐hydroxy ketones and α‐amino ketones were obtained with high yields and enantioselectivities.