Microwave assisted, one-pot synthesis of 5-nitro- 2-aryl substituted-1H-benzimidazole libraries: Screening in vitro for antimicrobial activity

Abstract

The efficient and rapid synthesis of 5-nitro-2-aryl substituted-1H-benzimidazole libraries (1a-1j) has been established. Thus, both microwave and conventional cyclo-condensation of 4-nitro ortho-phenylenediamine with various phenoxyacetic acids were carried out in the presence of HCl catalyst. The microwave synthesis route afforded advantages, such as good to excellent yields, shorter reaction time (2.5–3.5 min), readily available starting material, and simple purification procedure, which distinguish the present protocol from other existing methods used for the synthesis of benzimidazole libraries. Bioassay indicated that all the compounds showed in vitro antimicrobial activity against Vancomycin resistant enteroccoccus, Staphylococcus aureus, Micrococcus, Bacillus subtilis (gram-positive bacteria) and Shigella dysentery, Escherichia coli (gram-negative bacteria) and Candida albicans, Aspergillus niger, Penicillium (fungi). The minimum inhibitory concentration (MIC) was determined for test compounds as well as for reference standards.

Keywords::

• Benzimidazole libraries
• one-pot synthesis
• microwave irradiation
• antimicrobial activity

Acknowledgements

This research work is financially supported by the Department of Science & Technology (DST), New Delhi - 110 016. (Ref. No SR/S1/OC-08/2005 dated 05-09-2005).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.