Syntheses of arylcinnamic acids, using Alum-Cs2CO3 as precursors of new 2-heterostyrylbenzimidazoles and their antimicrobial evaluation

• Published in: Medicinal chemistry research 2015-03, Vol.24 (3), p.1351-1364
• Main Authors: Ashok Kumar, T., Kishore Babu, P. N., Rama Devi, B.
• Format: Article
• Language: English
• Subjects: Biochemistry; Biomedical and Life Sciences; Biomedicine; Cell Biology; Original Research; Pharmacology/Toxicology
• ISSN: 1054-2523; 1554-8120
• DOI: 10.1007/s00044-014-1208-5

A simple and green methodology has been developed for the syntheses of some new 2-styrylbenzimidazoles. In this method, 2-styrylbenzimidazoles 6(a – x) were synthesized by the condensation of o -phenylenediamines 4(a – c) with cinnamic acids 3(a – h) using glycerol containing boric acid (10 mol%) as the reaction medium at 180 °C about 3–5 h. The cinnamic acids 3(a–h) were obtained by the condensation between aromatic aldehydes 1(a – h) , and malonic acid using a new heterogeneous catalytic system such as alum-Cs 2 CO 3 in water is described. Compounds 6(a–x) were also obtained alternatively by the condensation of 2-methylbenzimidazoles 5(a-c) with 1(a-h) using the same glycerol containing boric acid (10 mol%) as reaction medium at 180 °C for 5–6 h. The catalytic systems mentioned here were found to be highly active, stable, and recyclable under reaction conditions. All the newly synthesized compounds were characterized by IR, Mass, and NMR spectral analyses. All synthesized compounds were screened for their antimicrobial activity against the clinical strains which include gram-positive bacteria ( Micrococcus luteus MTCC 2470, Staphylococcus aureus MTCC 96, Staphylococcus aureus MLS-16 MTCC 2940, Bacillus subtilis MTCC 121) and gram-negative bacteria ( Escherichia coli MTCC 739, Pseudomonas aeruginosa MTCC 2453, Klebsiella planticola MTCC 530, and Candida albicans MTCC 3017). The results revealed that compounds ( 6b , 6g , 6h , 6j , 6k , 6n , 6o , 6t ) exhibited significant antibacterial activity almost equal to the standard drug, i.e., Ciprofloxacin.