Regioselective differentiation of vicinal methylene C-H bonds enabled by silver-catalysed nitrene transfer

Silver-catalyzed nitrene insertion enables the formation of benzosultams in good yield and with regioselectivity complementary to other transition metal nitrene-transfer catalysts. Preferential formation of six-membered benzosultam rings predominates for alkyl-substituted benzenesulphonamide precursors. Ligand-controlled tunability is also achieved for benzenesulphonamides with gamma-branched alkyl substituents. Mechanistic probes suggest that the reaction pathway differs depending on whether a alpha (benzylic) or beta (homobenzylic) C-H bond undergoes amidation, as well as the catalyst identity.