1 H -Pyrazolo[3,4- b ]pyridines: Synthesis and Biomedical Applications.

Pyrazolo[3,4- b ]pyridines are a group of heterocyclic compounds presenting two possible tautomeric forms: the 1 H - and 2 H -isomers. More than 300,000 1 H -pyrazolo[3,4- b ]pyridines have been described which are included in more than 5500 references (2400 patents) up to date. This review will cover the analysis of the diversity of the substituents present at positions N1, C3, C4, C5, and C6, the synthetic methods used for their synthesis, starting from both a preformed pyrazole or pyridine, and the biomedical applications of such compounds.