Microwave accelerated solvent-free synthesis and antifungal evaluations of flavanones

Abstract

Microwave irradiation of 2-hydroxy chalcones under solvent-free conditions resulted in a "green-chemistry" procedure for the preparation of flavanones in good yields, using an unmodified household microwave oven and silica as solid support. By irradiation of 2-hydroxy chalcones with trifluoroacetic acid over silica gel, 11 known flavanones were prepared in high yields. The synthesised compounds were characterised using spectroscopic techniques, namely, 1H NMR, 13C NMR and IR, and screened for their antifungal activity in vitro against Sclerotium rolfsii and Rhizoctonia solani by poisoned food technique. The compounds tested were found to be more active against R. solani, whereas against S. rolfsii, moderate activity was observed, as evident from LC 50 values. The most potent compound 2-(4-fluorophenyl)-2,3-dihydrochromen-4-one (4a) had LC 50 value of 12.0 mg L -1 followed by 11, 11a, 3a, 9a, 8a, 10a and 10 having LC 50 values 18.21, 18.3, 32.9, 50.7, 88.8, 118.8 and 119.7 mg L -1, respectively. © 2011 Copyright Taylor and Francis Group, LLC.