Eco-friendly synthesis and antimicrobial activities of some 1-phenyl-3(5-bromothiophen-2-yl)-5-(substituted phenyl)-2-pyrazolines

BACKGROUND: Green catalyst fly ash: H(2)SO(4) was prepared by mixing fly ash and sulphuric acid. Microwave irradiations are applied for solid phase cyclization of 5-bromo-2-thienyl chalcones and phenyl hydrazine hydrate in the presence of fly ash: H(2)SO(4) yields, 1-phenyl-3(5-bromothiophen-2-yl)-5-(substituted phenyl)-2-pyrazolines. These pyrazolines were characterized by their physical constants and spectral data. The antimicrobial activities of all synthesized pyrazolines have been studied. RESULTS: Scanning electron microscopy (SEM) analysis shows the morphology changes between fly ash and the catalyst fly ash: H(2)SO(4). The SEM photographs with the scale of 1 and 50 μm show the fly-ash particle is corroded by H(2)SO(4) (indicated by arrow mark), and this may be due to dissolution of fly ash by H(2)SO(4). The yields of 1-phenyl-3(5-bromothiophen-2-yl)-5-(substituted phenyl)-2-pyrazolines is more than 75% using this catalyst under microwave heating. All pyrazolines showed moderate activities against antimicrobial strains. CONCLUSION: We have developed an efficient catalytic method for synthesis of 1-phenyl-3(5-bromothiophen-2-yl)-5-(substituted phenyl)-2-pyrazolines by solid phase cyclization using a solvent-free environmentally greener catalyst fly ash: H(2)SO(4) under microwave irradiation between aryl chalcones and hydrazine hydrate. This reaction protocol offers a simple, economical, environment friendly, non-hazardous, easier work-up procedure, and good yields. All synthesized pyrazoline derivatives showed moderate antimicrobial activities against bacterial and fungal strains.