Microwave Synthetic Laboratory, Department of Chemistry, College of Science, M. L. Sukhadia University, Udaipur-313 001, Rajasthan, India E-mail : rituvyas_23@yahoo.co.in PI Industries Ltd., Udaisagar Road, Udaipur-313 001, Rajasthan, India Manuscript received 2 September 2008, accepted 1 October 2008 Rapid and efficient methods for the preparation of a set of isoxazole, pyrazole and pyrimidine derivatives of imidazolinone and quinazolinone by the reaction of 5-substituted arylidene-{2-(imidazolyl/quinazolyl)imino }thiazolidinone (chalcones) with hydroxylamine, urea and hydrazine hydrate under MWI are reported. Excellent yields and higher purity are obtained in MW enhanced synthesis as compared to the conventional procedure which required exceedingly long reaction times, high temperatures and tedious workups. The potent antimicrobial effects of the synthesized compounds were investigated.