Synthesis and antimicrobial activity of some novel quinoline-pyrazoline-based coumarinyl thiazole derivatives

A series of novel 3-(2-(5-(2-chloroquinolin-3-yl)-3-substituted phenyl-4,5-dihydro-1H-pyrazol-1-yl)thiazol-4-yl)-6-H/halo-2H-chromen-2-ones (9a-9y) was prepared as antimicrobial agents by the condensation of 3-(2-bromoacetyl)-6-H/halo-2H-chromen-2-ones (4a-4e) and 5-(2-chloroquinolin-3-yl)-3-substituted phenyl-4,5-dihydro-1H-pyrazole-1-carbothiamide (8a-8e) in ethanol. The structures of these compounds were confirmed on the basis of their infrared, H-1-nuclear magnetic resonance, C-13-nuclear magnetic resonance, mass and elemental analysis data. The antimicrobial activity of these compounds was determined by the serial plate dilution method. The compounds with fluoro-substituted coumarin ring along with the fluoro-substituted phenyl ring, 9q, 9r, and 9s, produced better and potent antimicrobial activity than their corresponding H/chloro/iodo/bromo-substituted analogs with statistically significant results (p < 0.05). The compounds 9q and 9r also produced higher antifungal activity than standard drug ketoconazole against Penicillium citrinum. However, these compounds required higher concentration than standard drugs, ofloxacin, and ketoconazole, to produce these effects. The structural modification of these compounds may enhance their potency as antimicrobial agents, but this requires further studies.