4-(4-Chlorophenyl)-3,4-dihydro-6-methyl-5-(4-tolyl)carbamoyl-2(1H)-pyrimidinethione (1) wasreacted with benzylidenemalononitrile or ethyl cyanocinnamate to afford the pyrimidothiazine derivatives 2 and 4. Treatment of 1 withN,N-dimethylformamide-dimethylacetal (DMF-DMA) afforded 5. Acetylpyrimidine derivative 7 was produced upon treatment of 1 with mixture of acetic anhydride and acetic acid. Compound 1 was treated with chloroacetic acidto give the 5-(4-Chlorophenyl)-7-methyl-3-oxo-6-(4-tolyl)-carbamoyl-2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine (8), thione 1 was cyclized to 2-benzylidenethiazolopyrimidine derivatives 9a,b upon reaction with chloroacetic acid and aldehydes, also compound 1 was treated with 1,2-dichloroethane to give 5-(4-chlorophenyl)-7-methyl-6-(4-tolyl)carbamoyl-2,3-dihydro-5-H-[1,3]thiazolo[3,2-a]pyrimidine(10). The hydrazine derivative 11 was prepared by boiling 1 with hydrazine. Reaction of 11 with ethyl acetoacetate, DMF-DMA, acetic anhydride and 4-chlorobenzaldehyde gave 2-pyrazolylpyrimidine 12, 4-(4-Chlorophenyl)-2-(N,N-dimethylaminomethylene)hydrazino-6-methyl-5-(4-tolyl)carbamoylpyr- imidine (13), acetylhydrazinyl derivative 15 and 4-(4-Chlorophenyl)-2-(4-chlorophenylmethylenehydrazone)-6-methyl-5-(4-tolyl)carbamoylpyrimidine (16), respectively.