Synthesis of Cyclic Sulfilimines and Sulfoximines via Copper-Mediated C(sp2)–H Sulfanylation of Benzylamines with a Catalytic Transient Directing Group

C─H functionalization presents opportunities to streamline the synthesis of valuable molecular structures. This study details the development of a copper-mediated, transient C(sp²)–H sulfanylation of benzylamines with a transient directing group (TDG). Subsequent oxidative cyclization forms novel cyclic sulfilimines and sulfoximines, emerging heterocyclic scaffolds with attractive properties for drug discovery. Crucially, sulfenamides are identified as effective sulfanylating reagents for the C─H sulfanylation with catalytic 2-hydroxynicotinaldehyde as the TDG. Unconventionally, sulfenamides provided a slow release of the essential sulfanyl radicals through a thermally induced homolytic cleavage of the N─S bond, supported by mechanistic studies including electron paramagnetic resonance spectroscopy and radical quenching experiments. The sulfide products are then readily diversified at sulfur and nitrogen, including through cyclization.