Eighteen novel 5-phenyl-3-(substitutedthioxoquinazolinonyl) isoxazoles (5a-r) were synthesized by cycloaddition of various chalcones with hydroxylaminehydrochloride (NH2OH.HCl). All the newly synthesized compounds were confirmed by their spectral and analytical data. They were evaluated for antimicrobial, antihelminthic, analgesic and anti-inflammatory activities with an objective to evaluate the effect of thioxoquinazolinone substituted isoxazoles. Compounds 5a, 5f, 5g, 5k and 51 showed significant antimicrobial, anthelmintic, analgesic and anti-inflammatory activities. Further, isoxazoles having bromo substituted thioxoquinazolinones exhibited excellent activities than iodo substituted thioxoquinazolinones.
