Ring-chain isomerism of imines of N-monosubstituted 2-benzoylbenzenesulfonamides

Imines of N-monosubstituted 2-benzoylbenzenesulfonamides or their ring isomers, viz., 3-amino-3-phenylbenzoisothiazoline 1,1-dioxides, were synthesized by condensation of the dilithium derivatives of N-monosubstituted benzenesulfonamides with benzonitrile. Interconversions of the isomers were realized for the N-phenyl derivative. The introduction of bulky isopropyl or tert-butyl substituents at the sulfonamide nitrogen atoms stabilizes the open structure. The ring isomers of the N-acylimines, viz., 3-acylamino-3-phenylbenzoisothiazoline 1,1-dioxides, are formed exclusively in the acylation of both the open and ring isomers.