Syntheses and properties of 3‐acylimino‐1‐alkylimidazolium and benzimidazolium betaines

Abstract

Abstract3‐Amino‐1‐alkylimidazolium and benzimidazolium mesitylenesulfonates were readily prepared in good to high yeilds by treating the parent heterocycles with O‐mesitylenesulfonylhydroxylamine. Treatment of the 3‐amine salts with acylating agents gave crystalline 3‐acylimines, which showed the characteristic ir, uv, nmr, and mass spectral properties. Deuterium exchange of the 3‐acylimines occurs at the 2‐position. Thermolysis of neat 3‐benzoylimino‐1‐rnethylbenzimidazolium betaine afforded 2‐benzamido‐1‐methylbenzimidazole and products derived from NN bond cleavage. Irradiation of 3‐benzoylimino‐1‐alkylbenzimidazoliurn betaines resulted in NN bond cleavage to give 1‐alkylbenzimidazoles and benzamide, while the corresponding 3‐ethoxycarbonylimines underwent rearrangement to afford ethyl 1‐alkyl‐2‐benzimidazolecarbamates.