Vk. Ahluwalia et A. Dahiya, SYNTHESIS OF PYRAZOLO[3',4' 5,6]PYRIDO[2,3-D]PYRIMIDINES/, Indian journal of chemistry. Sect. B: organic chemistry, including medical chemistry, 35(11), 1996, pp. 1208-1210
Cyclocondensation of 3-alkyl(or aryl)5-amino-4-formyl-1-phenyl-1H-pyra
zoles 2a-c with cyanoacetamide in the presence of sodium methoxide in
absolute methanol gives 3-alkyl(or amido-6-amino-1-phenyl-1H-pyrazolo[
3,4-b]pyridines 3a-c, Acetyla tion of 3a-c with acetic anhydride and a
cetic acid at reflux followed by cyclization affords 3-alkyl(or aryl)-
7-methyl-5-axo-1-phenyl-(1H, 6H)-pyrazolo[3',4' : 5,6]pyrido[2,3-d]pyr
imidines 5a-c.