Chloroacylation of 3-amino-2-phenylpyrazole-4-carboxamide (2) using chloroacetyl-(propionyl) chloride
affording 6-chloromethyl(ethyl)-1-phenylpyrazolo[3,4-d]pyrimidin-4[5H]-one (3) or (6). Chlorine atom in compound
(3) or (6) underwent nucleophilic substitution reaction with primary or secondary amines to give
6-alkyl(aryl)aminomethyl(ethyl)-1-phenylpyrazolo[3,4-d]pyrimidin-4[5H]-one (4a-g,7a-f). When arylaminomethyl(
ethyl)pyrazolopyrimidine was treated with formaline (30%) solution in ethanol, underwent Mannich
reaction to afford imidazopyrazolopyrimidines (5a-e) and pyrazolopyrimidopyrimidines (8a-e). Chloromethylpyrimidine
derivative 3 was converted into the corresponding mercaptomethylpyrazolopyrimidene 9, Which
cyclized using bromomalononitrile or phenacyl bromide into pyrazolopyrimidothiazine 11,12