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Ecofriendly Synthesis of Chalcones and their 2-Pyrazoline and Isoxazolines Derivatives as Potential Microbial Agents

Bhupendra Kumar Sharma, Suresh C. Ameta and Vijay Kumar Dwivedi

Microwave assisted synthesis of chalcones unde r solvent-free conditions resulted in a “green- chemistry” procedure for the prepar ation of 2-pyrazolines and isoxazoline derivatives in very good yields. Acetone was reacted with appropriately substituted benzal dehydes in the presence of basic alumina to furnish substituted chalcones (1 , 2 and 3) . These chalcones undergo facile and clean cyclization with phenyl hydrazine, 2,4-dinitrophenylhydrazine, semicarba zide and thiosemicarbazide to afford substituted 3,5-arylated-2-pyraz oline derivatives (1a-1d , 2a-2d and 3a-3d) . Reaction of these chalcones with hydroxylamine hydrochloride yielded 3, 5-arylated isoxazoline derivatives ( 1e , 2e and 3e) . The structures of synthesized compounds have been confirmed by suitable spect roscopic techniques such as IR and 1 H NMR and analytical data. All the compounds were screened for their antib acterial activity against Staphylococcus aureus , Escherichia coli and Pseudomonas aeruginosa and for antifungal activity against Candida albicans and Aspergillus fumigatus. The compounds exhibited moderate to excellent antibacterial and antifungal activities. The results obtained indicate that unlike classical heating, microwave irradiation results in higher yields in shorter reaction times and cleaner reactions in eco-friendly manner.