2-Acetyl-6-cyano-7-ethyl-3-methylthiazolo[3.2-a]-pyrimidine-S-one (3) prepared by reaction of compound (1) with 3-chloropentan-2.4-dione followed by ring closure, was used as starting material to synthesise other heterocyclic compounds. The acetyl compound (3) was easily condensed with different amines to produce the imines (4-8). or the corresponding chalcone (9) when allowed to react with an aromatic aldehyde in presence of zinc chloride. Coupling of compound (3) with benzene diazonium chloride gave the phenylazo derivative (10). When compound (4) was treated with a-haloketones or a-haloesters, the thiazoline or thiazolidine compounds (11-15) were produced. Compound (15) was condensed with aromatic aldehydes to give the corresponding arylidene-derivatives (16a-c). Finally the chalcone (9) was reacted with hydrazine hydrate, phenyl hydrazine and hydroxyl amine to give pyrazolo and isoxazole compounds (17-19) respectively.