SYNTHESIS AND ANTIMICROBIAL ACTIVITY OF SOME NOVEL COUMARIN ANALOGUES

The desired target Compounds (4a-e), (5a-e) and (6a-e) were prepared in two steps. Reaction of 3-acetyl-6-bromo-2H-chromen-2-one (1) with 3-(Aryl)-1-phenyl-1H-pyrazole-4-carbaldehydes (2a-e) in presence of aqueous KOH solution and the reaction mixture stirred  for 2 hours and then filtered, furnished the desired 6-bromo-3-((E)-3-(3-(Aryl)-1-phenyl- 1H-pyrazole-4-yl) acryloyl)- 2H-chromen-2- ones (3a-e) crystalline solids in 60-70% yield (Scheme-1). Further, compounds (3a-e) reaction with thiourea, urea and hydrazine hydrate in the presence of a base in EtOH yielded the compounds (4a-e), (5a-e) and (6a-e) in 50-85% yield. All the synthesized compounds have been characterized by spectral data’s, and they are screened for anti-microbial activity. Among synthesized compounds 3b, 3c, 3d, 5a, and 5d exhibited good activity against bacterial strains S. aureus, P. aeruginosa, and E. coli, respectively. Whereas other compounds showed poor to moderate activity against all bacterial strains and compounds 3a, 3b, 3d, 4c, 5d, and 5c exhibited good antifungal activity against A. niger, and A. flavus and remaining compounds exhibited moderate antifungal activity. Results were tabulated in Table 2.