Thermal solvent-free synthesis of novel pyrazolyl chalcones and pyrazolines as potential antimicrobial agents

A novel approach was adopted for the synthesis of series of new pyrazolyl chalcones (3a–c) by the reaction of 5-chloro-3-methyl-1-phenylpyrazole-4-carboxaldehyde (1) with different 5-acetylbarbituric acid derivatives (2a–c) under thermal solvent-free condition. The chalcones were then converted to the corresponding pyrazolines (4a–c) under the same condition in excellent yields. All the synthesized compounds were characterized using elemental analysis and spectral data (IR, 1H NMR, and mass spectrometry). The synthesized compounds were tested for their antimicrobial activity by disk diffusion assay with slight modifications against Gram-positive, Gram-negative strains of bacteria as well as fungal strains. The investigation of antimicrobial screening revealed that compounds (3a–4c) showed good antibacterial and antifungal activities, respectively. Among the screened compounds, 3b showed more potent inhibitory activity (MIC = 12.5 μg/ml) nearly to that of standard antibiotics ciprofloxacin, griseofulvin and fluconazole.

Graphical abstractA novel series of pyrazolyl chalcones (3a–c) and pyrazolines (4a–c) were synthesized under thermal solvent-free condition and were screened for their in vitro antibacterial and antifungal activities.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Green synthesis of a novel series of pyrazolyl chalcones and pyrazolines employing easily available starting materials. ► Pyrazolyl chalcones and pyrazolines are obtained in excellent yields, shorter time period and involving simple operational procedure. ► In vitro antibacterial and antifungal evaluation of various pyrazole derivatives have proved as potential antimicrobial agents.