Synthesis of pyrimidines, thienopyrimidines, and pyrazolopyrimidines

Article abstract of DOI:10.1080/10426500214894

5-Ethoxycarbonyl-4-methyl-2-phenylpyrimidin-6(1H)-thione (3), which was prepared from the reaction of ethyl β-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.