Investigation of O‐Sulfonylation‐promoted Heterolytic NO Bond Cleavage of Amidoximes and Ketoximes

Two different reaction pathways were observed in the sulfonylation of N‐phenylbenzamidoximes. The reaction with o‐NsCl at a heating temperature gave N,N′‐diphenylureas via Tiemann rearrangement, while the reaction with Ts2O at a lower temperature formed 2‐phenylbenzimidazoles via intramolecular electrophilic aromatic substitution. When the amide nitrogen was replaced with carbon substituents, oxime derivatives of benzoins and benzils underwent Beckmann fragmentation reactions upon sulfonylation, whereas sulfonylation of 2‐phenylacetophenone oxime afforded exclusively the Beckmann rearrangement adduct.