Synthesis of some Pyrido [2',3': 3,4] Pyrazolo [1,5-a] Pyrimidine, [1,5-a] -1,3,5-Triazine and [5,1-c] -1,2,4-Triazine derivatives

ABSTRACT

The synthesis of pyrido [2',3'3,4]-pyrazolo [1,5-a] pyrimidine, pyrido [2',3'3,4] pyrazolo [1,5-a]-1,3,5-triazine and pyrido [2',3' 3,4] pyrazolo [5,1-c]-1,2,4-triazine derivatives from aminopyrazole- [3,4-b] pyridine derivative was reported. 3-Amino-4-[4-chlorophenyl]- 6-methyl-1H-pyrazolo[3,4-b] pyridine-5-carboxanilide [II] was prepared by heating 4-[4-chlorophenyl]-6-methyl-2-methylthio-5-phenylcarbamoyl- pyridine-3-carbonitrile [1][11] with hydrazine hydrate in n-butanol. Compound II gave compatible elemental analyses and spectral data [experimental]. Compound II behaved typically as 3-aminopyrazoles. Thus, it added to benzoyl isothiocyanate in boiling pyridine to give sym-disubstituted thiourea derivative III rather than the substituted aminopyrazole derivative IV. The assignment of structure III to the reaction product was inferred from its 1H-NMR spectrum [[2H6]DMSO] study, which showed signals at delta 2.67 ppm [s.3H.CH3], 6.96-7.87 [m,14H, aromatic protons], 10.52 [s,1H,NH,D2O exchangeable], 11.51 [s, 1H,NH.D2O exchangeable], 11.89 [s,1H,NH,D2O exchangeable] and 13.78 [s,1H,NH,D2O exchangeable]. The 1H-NNM data favors structure III over IV due to the appearance of four types of exchangeable