Catalytic Reductive Cross Coupling and Enantioselective Protonation of Olefins to Construct Remote Stereocenters for Azaarenes

Abstract

A novel enantioselective protonation protocol that is triggered by reductive cross coupling of olefins is reported. When under cooperative photoredox and chiral hydrogen-bonding catalytic conditions and using a terminal reductant, various alpha-branched vinylketones with diverse vinylazaarenes could provide important enantioenriched azaarene derivatives containing tertiary stereocenters at their remote delta-position with high yields and enantioselectivities. This reaction system is also suitable for alpha-branched vinylazaarenes, thus successfully assembling elusive 1,4-stereocenters. The convenient late-stage modifications of products, especially the formation of remote epsilon-tertiary and epsilon-heteroquaternary carbon stereocenters, further highlight the important synthetic value of this method. Control experiments and density functional theory (DFT) calculations were conducted to elucidate the plausible reaction mechanism and origins of regioselectivity and stereoselectivity.