Сyclization of 1-amino-2-hydrazinobenzimidazole treated with carbon disulfide. Synthesis of 9-amino-2,9-dihydro-3 Н-[1,2,4]triazolo[4,3- а]benzimidazole-3-thione and its derivatives.

1-Amino-2-hydrazinobenzimidazole when treated with carbon disulfide underwent a regioselective cyclization involving the hydrazino group to form 9-amino-2,9-dihydro-3 Н-[1,2,4]triazolo[4,3- а]benzimidazole-3-thione. Being an N-amine this compound gives Schiff bases with aromatic aldehydes, and as thione in DMF at a temperature not exceeding 60°С it is successfully alkylated, particularly by functionalized alkylating agents, affording the corresponding sulfanylmethyl derivatives. In boiling DMF, as it is demonstrated by an example of benzyl chlorides, NNH group also undergoes alkylation that unexpectedly results in 4-benzylidenamino-3-benzylsulfanyltriazolobenzimidazoles. [ABSTRACT FROM AUTHOR]