Radical Sulfinamidation of Alkenes Enabled by a PCET-HAT Relay.

Sulfinamides and related sulfur(VI) motifs are widely represented in bioactive molecules; however, their direct installation onto alkenes has traditionally relied on Lewis acid- or transition metal-mediated two-electron pathways, with more recent advances dominated by photoinduced single-electron processes. Here, we report a metal- and light-free radical sulfinamidation of alkenes that proceeds through a radical chain mechanism enabled by a proton-coupled electron transfer-hydrogen atom transfer (PCET-HAT) relay, initiated by trace amounts of oxygen. This transformation operates under operationally simple conditions, enabling rapid access to structurally diverse sulfinamides with broad substrate scope and excellent functional group tolerance. The synthetic utility of this strategy is demonstrated by the late-stage functionalization of complex natural products and drug molecules. Mechanistic investigations combining experimental studies and density functional theory calculations reveal a PCET-initiated radical chain process in which a HAT event relays reactivity to generate sulfinyl radicals, accounting for the high efficiency and selectivity of the reaction. This work establishes a mechanistically distinct platform for alkene sulfinamidation and highlights the potential of radical chain processes enabled by PCET-HAT relays in synthetic chemistry.