Synthesis of pyrimidines, thienopyrimidines, and pyrazolopyrimidines

5-Ethoxycarbonyl-4-methyl-2-phenylpyrimidin-6(1H)-thione (3), which was prepared from the reaction. of ethyl beta-aminocrotonate 1 with benzoyl isothiocyanate (2) in refluxing acetone, was reacted with a series of halopgenated reagents to give S-alkyl derivatives 4a-g. Upon treatment of compounds 4a-c with sodium ethoxide were cyclized into thienopyrimidine 10a-c. Pyrimidinethione 3 was reacted with hydrazine hydrate to give hydroxypyrazolopyrimidine derivative 6. The later compound was obtained by heating compound-4a with hydrazine hydrate under neat conditions, but when the reaction was carried using hydrazine hydrate in ethanol, the corresponding carbohydrazide 5 was produced.