Here is the report of an environment friendly, rapid, and convenient one-pot ultrasound-promoted synthesis of 5-amino-2-(4-chlorophenyl)-7- substituted phenyl-8,8a-dihydro-7H-[1,3,4]thiadiazolo[3,2-a]pyrimidine-6-carbonitrile derivatives. Multi-component reactions are useful for the creation of chemical libraries of drug-like compounds with levels of molecular complexity and diversity. 1,3,4-Thiadiazolo[3,2-a]pyrimidine skeleton belongs to a well-known and important class of fused heterocycles prevalent in a number of natural products of biological activities including antitumor, fungicidal, antibacterial, and herbicidal, hence, prompted us to synthesis 1,3,4-Thiadiazolo[3,2-a]pyrimidines. The final ten derivatives were obtained in excellent yield through a one-pot, three component condensation reaction of aldehyde, 4-chlorophenyl-2-aminothiadiazole, and malononitrile in 10-12 ml of ethanol as solvent and sodium hydroxide as a catalyst. (VCX 500-220, Ultrasound Solid probe, irradiation at 80⁰C and 20% amplitude).

We have carried out the same reaction by conventional method, which requires 9-10 hrs of refluxing and yield is lesser. Because of the advantage of faster reaction rates and better yields, use of Ultrasound solid probe, was found to be more suitable for this reaction. Structure of the synthesized derivatives was confirmed by IR, NMR and Mass spectral study.