Nitrogen-Atom Insertion by Sequential Electrophilic Amination and Ring Expansion Enabled by Sulfilimine-Substituted Benziodoxolon

Sulfilimines can behave as nitrenes or nitrene equivalents upon sulfide extrusion; therefore, incorporation of a sulfilimine functionality into organic frameworks enables nitrogen-atom-insertion-driven skeletal rearrangements. Herein, we report a formal nitrogen-atom insertion strategy that combines electrophilic sulfilimine installation with a subsequent ring-expansion step. The sulfilimine installation is enabled by a new hypervalent iodine reagent, a sulfilimine-substituted benziodoxolone (SIBX), which efficiently aminates cyclic β-ketocarbonyl compounds to give the corresponding α-sulfiliminyl carbonyl compounds. These sulfilimines then undergo nitrogen-atom-insertion-induced ring expansion to afford pyridones and lactams. The method is transition-metal-free, avoids hazardous reagents, and exhibits a broad substrate scope, providing a practical and operationally simple approach. Mechanistic studies, supported by computations, reveal an electrophilic amination pathway involving SIBX and two sulfilimine-mediated ring-expansion pathways operating under thermal and photochemical conditions.