Microwave-Induced Synthesis of Substituted Isoxazoles as Potential Antimicrobial Agents

Background: A convenient synthesis of series of functionalized 5-(substituted phenyl)-3phenylisoxazole (4a-f) has been carried out by using established procedures. First of all, alpha,beta-unsaturated carbonyl compounds, Chalcones (3) were synthesized by reacting different substituted benzaldehydes (1) with acetophenone (2) based on the mechanism involved in Claisen-Schimidt condensation. Methods: Various Isoxazole derivatives (4a-f) were prepared by the reaction of Chalcones (3) with hydroxylamine hydrochloride in the presence of sodium acetate with the help of both microwave and conventional heating methods to compare their product yields and reaction time. The newly synthesized compounds were characterized by IR, H-1 NMR spectral data and thin layer chromatography. Results: It is noteworthy that the synthetic reaction which requires 6-8 h in conventional method (yield 58-69%) was completed within 6-10 minutes by microwave irradiation synthesis with improved yield (67-82%). So, the use of microwave accelerated synthesis results in improvement of reaction rate, high yield in shorter reaction time and selectivity by reducing formation of waste products. Conclusion: The antimicrobial activities of titled compounds were evaluated in vitro against various strains of microorganisms. Some of these compounds exhibited pronounced antimicrobial activity in comparison with standard drugs.