Umpolung-Driven Oxidative β -β Dimerization of Conjugated N-Sulfonylimines Enabled by Fluorinated NHCs

We herein disclose a unique oxidative β-β dimerization of conjugated N-sulfonylimines via umpolung reactivity mediated by fluorinated N-heterocyclic carbenes. The elusive key aza-Breslow intermediate was successfully isolated and characterized by single-crystal X-ray diffraction studies. This underwent net 1e– oxidation of aza-homoenolate upon treating with a hypervalent iodine reagent, and the successive tail-to-tail radical-coupling afforded the imidzolium-bound dicationic bis-enamide product. The comprehensive studies including single-crystal X-ray analysis elucidated the molecular structure and stereochemistry, revealing the formation of a sole diastereomer.