Reactions of 4-halogeno- and 4-methylthio-imidazolium salts with sulphide and methanethiolate ions

Abstract

1,3-Dimethyl-substituted 4-halogeno- or 4-methylthio-substituted imidazolium salts undergo reaction with sulphur nucleophiles accompanied by (i) ring cleavage to give N-methylthioamides (chloro derivatives with sulphide ions), (ii) replacement of halogen (chloro derivatives with methanethiolate), or (iii) reduction (bromo or methylthio derivatives with sulphide or methanethiolate ions). Subsequent thiation at C-2 leads to 2-thiones, the 4-bromo derivative yielding 1,3-dimethylimidazoline-2-thione, the 4-methylthio derivative 1,3-dimethyl-4-methylthioimidazoline-2-thione. The 4-methylthio-substituted imidazolium salt undergoes selective N-demethylation on heating in pyridine.