Synthesis and biological evaluation of some substituted benzimidazole derivatives

In the current research work, the title compounds 5-ethoxy- benzimidazole, were synthesized by nitration of phenacetin with concentrated nitric acid it gives N-(2-nitro-5-ethoxyphenyl) acetamide (I), which on reduction with alcohol gives 5-ethoxy-2-nitroaniline (II). Reaction of hydrazine hydrate with 5-ethoxy-2-nitroaniline produced 5-ethoxy ortho phenylene diamine (III). The substituted acids reacted with 5-ethoxy ortho phenylene diamine then yielded the corresponding 5-ethoxy-benzimidazole (IV). The identification and characterization of the synthesized compounds were carried out by Elemental analysis, melting point, Thin Layer Chromatography, FT-IR, NMR and Mass data. The synthesized compounds were evaluated for anti-tubercular activity. The test compounds were subjected to in vitro screening by the tube dilution technique employing the human virulent H₃₇R_V strain of M. tuberculosis. The test compounds IVa, IVc and IVd showed significant anti-tubercular activity against H37RV strain of Mycobacterium tuberculosis. The minimum inhibitory concentration (MIC) values were found in the range of 0.8 to 12.5 μg/ml compared with the standard drugs Isoniazid.