Dual photoredox/copper-catalyzed 1,4-sulfonylalkylation of alkenes

Abstract

The 1,4-difunctionalization of alkenes remains less explored in organic synthesis, primarily due to the challenges of suppressing competitive monofunctionalization and 1,2-difunctionalization. Herein, we report a dual photoredox/copper-catalyzed 1,4-sulfonylalkylation of alkenes using two identical alkene molecules to achieve the simultaneous installation of C–S and C(sp³)–C(sp³) bonds within long-chain carbon skeletons. This method utilizes sodium sulfinates as a sulfonyl source, which undergo single-electron transfer (SET) oxidation to generate a sulfonyl radical. The radical adds to one alkene and the resulting intermediate engages in a kinetically and thermodynamically driven relay addition to a second identical alkene. Ultimately, the distal radical undergoes cross-coupling with an alkyl radical generated from α-carbonyl alkyl bromides, furnishing the 1,4-sulfonylalkylation product. Notably, the dual photoredox/copper catalytic system ensures precise regulation of the radical addition and coupling sequence, effectively suppressing competing side reactions. Mechanistic studies, including light on/off experiments, cyclic voltammetry (CV) experiments, Stern–Volmer experiments, radical scavenging experiments, radical clock experiments and copper complex detection experiments, provide insights into the mechanism of this dual catalytic system.