Benzimidazole Annulated New Heterocyclic Compounds: Synthesis of New Polycyclic Pyrazole Derivatives

Several (3) new benzimidazole based polycyclic compounds of potential pharmaceutical interest have been prepared starting from 2-benzimidazolelyl (1,3-dioxo-2-indenylidene) acetonitrile. Unhypothesized, the C=N function of the plausible intermediates was released as HCN rather than a classical nucleophilic addition when treated with bidentate reagents such as hydrazines, 5-amino-1H-1,2,4-triazole, 5-amino-4-cyano-1H-pyrazole and 2-aminobenzimidazole. When compound 3 reacted with active acetonitrile derivatives it afforded new polyfunctional pyridines via elimination of HCN in addition to, new pyrimidine, pyrazine and azepine derivatives.