DESIGN& SYNTHESIS OF ISOXAZOLE DERIVATIVES FROM CHALCONES FOR ANTI-MICROBIAL ACTIVITY

Abstract

Isoxazole derivatives are important heterocyclic compounds known for their diverse pharmacological activities, including antimicrobial, anti-inflammatory, anticancer, and analgesic properties. The incorporation of an isoxazole ring into organic molecules often enhances their biological potential. In the present study, a series of chalcone intermediates were synthesized through condensation reactions and subsequently converted into corresponding isoxazole derivatives using hydroxylamine reagents.
METHODOLOGY: Five chalcone derivatives (AB-1 to AB-5) were synthesized by condensation reactions between benzaldehyde and various active methylene compounds or ketones in the presence of sodium hydroxide under controlled conditions. The reactions were carried out in ethanol medium with continuous stirring and temperature control. The formation of chalcones was monitored by TLC using ethyl acetate-based mobile phases. The obtained chalcone intermediates were further reacted with hydroxylamine or hydroxylamine hydrochloride in ethanolic medium under alkaline conditions. Cyclization reactions were performed under reflux at temperatures ranging from 70–80°C for 2–4 hours to obtain the corresponding isoxazole derivatives. The products were isolated by precipitation, filtration, washing with water, drying, and recrystallization. TLC analysis was employed throughout the synthesis to confirm completion of reactions and assess purity.
RESULTS: All five chalcone intermediates were successfully synthesized and converted into their respective isoxazole derivatives. TLC analysis revealed distinct spots with improved purity after recrystallization, confirming successful product formation. The cyclization of chalcones with hydroxylamine proceeded efficiently under alkaline reflux conditions, resulting in satisfactory yields of isoxazole derivatives. Among the synthesized compounds, AB-4 (3,5-diphenyl-4,5-dihydroisoxazole) showed the most efficient conversion and highest product purity, while AB-2 and AB-3 also exhibited good reaction completion and product formation. The synthesized derivatives displayed characteristic physical properties such as crystalline appearance, stability, and reproducible TLC profiles, indicating successful synthesis of the target heterocyclic compounds.
CONCLUSION: The present study successfully established an efficient synthetic route for the preparation of isoxazole derivatives via chalcone intermediates. The use of hydroxylamine-mediated cyclization provided a simple, economical, and reproducible method for isoxazole synthesis. TLC studies confirmed the successful formation and purity of the products. These synthesized isoxazole derivatives may serve as promising scaffolds for further pharmacological and biological investigations.