Investigation of O-Sulfonylation-promoted Heterolytic NO 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.