Two Step Synthesis, Characterization and anti-bacterial activity of series of 3-((5-chloro-1H-benzo[d]imidazol-1-yl)methyl)- 1,2,4-oxadiazoles

A mixture of 5-chloro-1H-benzo[d]imidazole 1, K2CO3 and 2-bromoacetonitrile in DMF was stirred at 60oC temperature for 8 hr. to afford compound 2. A mixture of 2-(5-chloro-1H-benzo[d]imidazol-1-yl) acetonitrile, NH2OH.HCl and triethylamine in dry DCM was stirred at room temperature for 8 hr. After the aromatic carboxylic acids and vilsmeier reagent were added, the resulting mixture stirred for further 7 hr at the same temperature to give the crude 1,2,4-oxadiazoles 4a-4l and also screened for anti-bacterial evaluation. Among them 4f, 4g, and 4h established more efficient bacterial inhibitory action against B. subtilis, with MICs of 3.12, 3.12, and 1.56 mg/mL, respectively, whereas typical streptomycin MICs were 6.25 mg/mL. Compound 4h has shown more potent activity against S. aureus, with an MIC value of 3.12 mg/mL, whereas compound 4f has shown equipotent activity against S. aureus, with an MIC value of 6.25 mg/mL. Compound 4K has shown equipotent activity against B. subtilis and good activity against S. aureus with MIC values of 3.12 mg/mL and 6.25 mg/mL.