Visible Light-Promoted Enantioselective Catalytic Alkylation of α-Ketoamides with Hydrocarbons

Abstract

Visible light-mediated enantioselective alkylation of carbonyls with hydrocarbons provides beneficial access to the synthesis of chiral alcohols in terms of atom economy. Herein, we disclosed a direct asymmetric alkylation of α-keto pyrazoleamides with hydrocarbons as C(sp³)–H donors for the preparation of tertiary α-hydroxy amides. Our method operates by synergistic catalysis involving Ir-based photoredox catalyst and chiral N,N′-dioxide-NiBr₂ complex enabled the addition reaction in good-to-excellent yield and enantioselectivity (up to 87% yield and 97% ee), competing successfully with the homocouplings. Based on the control experiments and spectrographic experiments, a possible radical addition mechanism triggered by Ir photoredox catalysis and bromine radical-participated hydrogen atom transfer of hydrocarbon was proposed.