Synthesis, characterization and biological evaluation of novel C-2 substituted benzimidazole heterocycles

A series of new 1-(1H-benzo[d] imidazol-2-yl)-3-methyl-4-(substituted phenylhydrazono)-1H-pyrazol-5(4H)-ones (4a-i) were synthesized by the condensation of 2-hydrazinyl-1H-benzo[d]imidazole (2) with ethyl-2-arylhydrazono-3-oxobutyrates (3a-i) in glacial acetic acid. Also, 3-(1H-benzo[d]imidazol-2-ylamino)-2-(7-hydroxy-substituted-2-oxo-2H-chromen/quinolin -3-yl)thiazolidin-4-one)s (7a-d) were prepared via the cyclisation of Schiff bases 3-((2-(1H-benzo[d]imidazol-2-yl)hydrazono)substituted)-7-hydroxy-4-methyl-2H-chromen/quinolin-2-one (6a-d) with thioglycolic acid in refluxing benzene. Structural assignments of these synthesized compounds were based on IR, 1HNMR, and Mass spectral data. The newly synthesized compounds (4a-i), (6a-d) and (7a-d) which possess a variety of heterocycles with benzimidazole as core nucleus were evaluated for their antimicrobial and anti-inflammatory activities by cup-plate method and formalin induced rat hind paw oedema method respectively.