Microwave assisted synthesis of some novel 2-pyrazoline derivatives as possible antimicrobial agents

Some new [3-(4-phenyl)-5-phenyl-4,5-dihydropyrazol-1-yl](pyridine-4-yl)methanones and 3-substituted phenyl-5-substituted phenyl-4,5-dihydro-pyrazole-1-carbothioamides have been synthesized employing microwave techniques and evaluated for antimicrobial activity. Substituted acetophenones (1) were reacted with appropriately substituted benzaldehydes (2) in the presence of ethanol to furnish substituted chalcones (3a-f). These chalcones were further treated with isonicotinic acid hydrazide (INH) to afford substituted [3-(4-phenyl)-5-phenyl-4,5-dihydropyrazol-1-yl](pyridine-4-yl)methanones (4a-f). Reaction of these chalcones with thiosemicarbazide yielded substituted 3,5-diphenyl-4,5-dihydro-1H-pyrazole-1-carbothioamides (5a-f). The structures of newly synthesized compounds (4a-f) and (5a-f) have been confirmed by suitable spectroscopic techniques such as IR and 1H NMR. All the compounds were screened for their antibacterial activity against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa and for antifungal activity against Candida albicans and Aspergillus niger The compounds exhibited moderate antibacterial and good antifungal activities. Compound 4b and 4d showed significant antifungal activity against A. niger and C. albicans, respectively.