Asymmetric Radical-Radical Cross-Coupling through Visible-Light-Activated Iridium Catalysis

Abstract

Combining single electron transfer between a donor substrate and a catalyst-activated acceptor substrate with a stereocontrolled radical-radical recombination enables the visible-light-driven catalytic enantio- and diastereoselective synthesis of 1,2-amino alcohols from trifluoromethyl ketones and tertiary amines. With a chiral iridium complex acting as both a Lewis acid and a photoredox catalyst, enantioselectivities of up to 99% ee were achieved. A quantum yield of <1 supports the proposed catalytic cycle in which at least one photon is needed for each asymmetric C-C bond formation mediated by single electron transfer.

Keywords: asymmetric catalysis; electron transfer; photoredox catalysis; radicals.