A Convergent Approach for the Synthesis of New Pyrazolyl Bipyridinyl Substituted Coumarin Derivatives as Antimicrobials

Some new 3-[3-(1-phenyl-3-aryl-1H-pyrazol-4-yl) acryloyl] coumarins 3a-f were synthesized (coumarin chalcones) by the condensation of various 3-acetyl coumarins 1 and appropriate 1-phenyl-3-aryl-1H-pyrazole-4-carbaldehyde 2. These coumarin chalcones 3a-f were then employed for the synthesis of pyrazolyl bipyridinyl substituted coumarins 7a-f, 8a-f, and 9a-f under Krohnke’s reaction condition. The characterization of all the synthesized compounds was carried out by elemental analysis, IR, ¹H-NMR, ¹³C-NMR, DEPT-135 and mass spectral analysis. In addition to that, in vitro antimicrobial competency of the title compounds was assessed against selected pathogens. Compounds 3b, 3e, 7b, 8b, 8c and 9b exhibited excellent antimicrobial activity and said to be the most proficient members of the series.