Photocatalytic Radical Addition to N1‐Allenyl Benzimidazoles: A Metal‐Free Route to Sulfonylated Benzimidazoles

A metal‐free, visible‐light‐driven radical sulfonylation of N1‐allenyl benzimidazoles with sodium sulfinates has been developed. Under mild photoredox conditions, a diverse array of aryl, heteroaryl, and aliphatic sulfinates efficiently couple with allenamide substrates to afford structurally diverse sulfonylated benzimidazoles in good to excellent yields. Mechanistic studies support a radical‐mediated pathway initiated by the single‐electron oxidation of the sulfinate anion. The transformation demonstrates excellent scalability to gram quantities without compromising efficiency. This operationally simple, transition‐metal‐free protocol offers a sustainable and versatile strategy for accessing biologically relevant sulfonylated heterocycles.