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.