Novel synthesis of 2-substituted aminobenzimidazoles from thiourea derivatives.

The use of different alkyl halides as effective cyclodesulfurizing agents was thoroughly studied. N-phenyl-,N'-[o-aminophenyl]-thiourea when treated with different alkyl halides gave rise to 2-phenyl-aminobenzimidazole. The optimum conditions for such cyclodesulfurization reaction were established by using eight equivalents of the alkyl halide, ethyl alcohol as solvent, and 8 h reflux. The reaction was also successfully applied to N-o-tolyl (benzyl or n-butyl)-N'-[o-aminophenyli1-thioureas to give rise to the corresponding 2-substituted aminobenzimidazoles.