Photoredox-controlled chemo-divergent, regio-, and stereoselective difunctionalization of olefins via switchable SO2 reintegration

Abstract

While radical difunctionalization offers substantial potential for molecular diversification, existing methodologies predominantly focus on styrenes and activated alkenes, leaving fundamental light olefins (e.g., ethylene and propylene) largely unexplored. Moreover, achieving stereoselective transformations of light olefins remains a formidable challenge. Here, we present a visible-light-mediated photoredox-catalyzed chemo-divergent and regioselective radical difluoromethylation/polyfluoroarylsulfonylation and difluoromethylation/polyfluoroarylation of structurally diverse alkenes through switchable sulfur dioxide reintegration. The method demonstrates broad applicability across styrenes, unactivated alkenes, and gaseous ethylene/propylene substrates. The photocatalyst functions as a switch, and Sodium difluoromethanesulfinate (CF2HSO2Na) acts as a bifunctional reagent, enabling controllable divergence radical conversion via radical-polar crossover pathways. Notably, chiral alcohol-derived polyfluoroarenes efficiently induce stereoselectivity control in the coupling of alkyl radicals with sulfur dioxide via dynamic kinetic resolution. Density functional theory calculations indicate noncovalent interaction between alkyl/aryl groups and polyfluorocarbons plays critical roles for the ultralong-distance (>9 atoms) stereochemical induction. The key to achieving chemo-divergent and stereocontrolled transformations lies in the precise sorting of a dynamic intermediate pool containing alkyl radicals, sulfonyl radicals, and anions.