Quinone-Initiated Photocatalytic Enantioselective Giese Radical Addition with Ethers, Thioethers, Amines, and Alkanes

Abstract

Photocatalytic enantioselective Giese radical addition with inert C(sp³)–H bonds represents a highly efficient and economically favorable approach to synthesizing diverse value-added chiral molecules from abundant feedstock. Herein, we disclose a quinone-initiated photocatalytic asymmetric Giese radical addition of α-substituted acrylamides with inert C(sp³)–H bonds by applying simple quinones as HAT photocatalysts in combination with a chiral N,N′-dioxide/praseodymium(III) catalyst. A wide array of ethers, thioethers, selenide, amines, and alkanes can smoothly transform into the corresponding chiral α-aryl amide derivatives with satisfactory enantioselectivities (68 examples, up to 95% ee) under mild conditions. Based on spectroscopy studies and control experiments, a quinone-initiated HAT catalytic cycle was proposed, and DFT calculations revealed that the interaction between quinone and chiral Lewis acid was essential for enantio-induction in the asymmetric back hydrogen atom transfer process.