Phosphorylation of Benzimidazole-2-thiones by Chloroethynylphosphonate

The reaction of chloroethynylphosphonates with N-substituted benzimidazole-2-thiones proceeded chemo- and regioselectively with the formation of cyclic zwitterions, namely alkyl (9 H -benzo[4,5]imidazo[2,1- b ]-thiazol-3-yl-4-ium)phosphonates. Chemo- and regioselective reaction of N -unsubstituted benzimidazole-2-thione with chloroethynylphosphonates led to the production of linear Z -1,2-bis(1 H -benzimidazol-2-ylsulfanyl)-ethenylphosphonates.