Substrate-initiated radical relay: redox-neutral iodo/bromo sulfoximination of alkynes

Abstract

A substrate-initiated radical relay is developed for the redox-neutral iodo/bromo sulfoximination of alkynes under mild, metal-free conditions. This strategy exploits the intrinsic oxidative potential of sulfoximidoyl chlorides to promote single-electron transfer with halide anions, generating sulfoximinyl and halogen radicals in situ without external oxidants or catalysts. The transformation delivers (E)-β-haloalkenyl sulfoximines in up to 96% yield with broad functional-group tolerance and excellent stereoselectivity. Mechanistic investigations supported by cyclic voltammetry and density functional theory calculations reveal that a substrate-driven single-electron transfer process governs radical formation and stereochemical control. The resulting β-haloalkenyl sulfoximines represent heteroatom-rich alkene scaffolds that may serve as useful intermediates for further molecular diversification in synthetic and medicinal chemistry. This redox-economical approach establishes a new mechanistic strategy for substrate-controlled radical difunctionalization in sulfoximine chemistry.