Visible-Light-Mediated Pyridine- N -oxide-Assisted Alkoxycarbonyl Chlorination of Alkenes via Iron-Catalyzed Radical Ligand Transfer

Abstract The scalable, catalytic alkoxycarbonylchlorination of alkenes from alkyloxalyl chlorides, generated in situ from oxalyl chlorides and alcohols, by a combination of 4-cyanopyridine-N-oxide and Fe(II)-bipyridine has been developed. A broad range of functional groups is tolerated with high regio- and chemoselectivity. The breadth of this protocol is demonstrated by the successful engagement of activated and unactivated alkenes, including late-stage functionalization of alkenes containing pharmacophores. Control experiments and mechanistic investigations, such as NMR, EPR, and radical trapping analyses, indicate that the in situ-formed alkyloxalyl chloride-pyridine-N-oxide adduct undergoes decarboxylative photoinduced N−O bond fragmentation to generate acyl radicals, whereas the Fe(II) catalyst acts as a redox-neutral electron shuttle and assists chloride transfer via a radical ligand transfer (RLT) pathway.