Visible-light-driven three-component reductive 1,2-diarylation of alkenes

The intermolecular alkene 1,2-diarylation provides straightforward access to polyarylalkanes but suffers from substrate limitation, requiring directing auxiliaries or prefunctionalized aryl components. Herein, we report the development of a photocatalytic strategy that enables a three-component 1,2-diarylation of alkenes under mild reductive conditions using simple tertiary alkylamine as the terminal reductant. Readily accessible aryl iodides and cyanides serve as the C(sp2) electrophiles to simultaneously install two different aryl moieties across the olefins with high regioselectivity. This protocol exhibits a broad substrate scope for all of aryl, heteroatom-substituted, and even unactivated alkenes and can be easily scaled up to the gram-scale. Mechanistic studies reveal a halogen-atom transfer (XAT) of aryl iodides to transient aryl radicals while a single-electron transfer (SET) of aryl cyanides to persistent aryl radical anions, both allowing for a regiocontrollable radical relay sequence.