Photoinduced boryl-oximation of alkenes via NHC-boryl radical generation

Abstract

Boryl-functionalization of C–C multiple bonds offers a powerful route to organoboron compounds. Traditional transition-metal-catalyzed methods face challenges such as toxic residues and poor functional group tolerance. Furthermore, the recently reported photoredox-catalyzed boryl-functionalizations remain dependent on tailored photocatalysts, including Ir^III(bpy)₃, Ir^III(bpy)₂(dtbbpy)PF₆ and 4-CzIPN. N-Heterocyclic carbene (NHC) boranes, as versatile precursors, enable C–B bond formation via photochemical boryl radical generation. Herein, we describe a metal-free radical chain transfer strategy for NHC-boryl radical generation through thiol-catalyzed hydrogen atom transfer, achieving boryl-oximation of alkenes with a broad substrate scope and high selectivity. The resulting α-boryloximes serve as versatile synthetic intermediates, enabling late-stage functionalization of pharmaceutical molecules and further product transformations. Mechanistic studies highlight the critical role of light irradiation in sustaining the radical process.