Synthesis of Imidazolium and Benzimidazolium Triiodides

1,3-(Di)acetonylimidazolium and -benzimidazolium triiodides were synthesized in a one-pot fashion by reactions of imidazole, 3-(1H-imidazol-4-yl)prop-2-enoic acid, benzimidazole, benzimidazol-2-amine, and 2-ethylbenzimidazole with 1-iodopropan-2-one and molecular iodine under solvent-free conditions in the absence of a base and catalyst at room temperature. The reaction of 1H-benzimidazole-2-thiol with 1-iodopropan-2-one and iodine afforded 2-(2-oxopropylsulfanyl)imidazolium triiodide. The reaction direction and yield did not change when 2-iodo-1-(thiophen-2-yl)ethanone was used instead of 1-iodopropan-2-one.