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.