Synthesis of Pyrazolo[3,4- b ]Pyridine and Pyrido[2′,3′:3,4]Pyrazolo [1,5- a ]Pyrimidine Derivatives

The synthesis of two series of 1-phenyl and 1H-pyrazolo[3,4-b]pyridine is described. Thus, reacting 5-amino-1-phenylpyrazole with chalcone analogues gave 4,6-diarylpyrazolo[3,4-b]pyridine derivatives. While, reacting the same starting material with benzylidene derivatives of ethyl cyanoacetate and malononitrile resulted in 4-oxo and 4-aminopyrazolo[3,4-b]pyridine derivatives, respectively. The synthesis of 3-amino-4,6-diarylpyrazolo[3,4-b]pyridines starting from pyridine was also described. Thus, chlorination of 4,6-diarylpyridone derivatives and their subsequent cyclisation with hydrazine hydrate afforded 3-amino-4,6-diarylpyrazolo[3,4-b]pyridines. Reaction of the latter compounds with acetylacetone, ethyl ethoxymethylenecyanoacetate and chalcone analogue gave the tricyclic pyrido[2′,3′: 3,4]pyrazolo[1,5-a]pyrimidines. The structures of the products were confirmed by spectral data.