Abstract:
A variety of 3-(5-(substituted-phenyl)-4,5-dihydro-1H-pyrazol-3-yl)-2H-chromen-2-one derivatives
3a–j were synthesized through microwave assisted thermal annulation of corresponding
a,b-unsaturated ketones (chalcones) 2a–j via hydrazinolysis. Chalcones 2a–j were
prepared from 3-acetyl-coumarin 1 which was previously accessed by Pechmann condensation
reaction of salicylaldehyde. The series of pyrazoline-based coumarin motifs 3a–j synthesized,
were structurally confirmed by analytical and spectral data. They were then evaluated
for their antimicrobial activities using agar diffusion method. The result showed that microwave
assisted method (MAM) for the reaction was remarkably successful and gave the targeted
products 3a–j in higher yields at shorter reaction times compared to conventional
synthetic method (CSM). The results showed that these skeletal frameworks exhibited
marked potency as antibacterial agents. The most active antibacterial agent was 3-(5-(4-
(diethylamino) phenyl)-4,5-dihydro-1H-pyrazol-3-yl)-2H-chromen-2-one 3j with MIC and MBC
values of 3.92 ± 0.22 mg/mL and 7.82 ± 0.43 mg/mL respectively.
