Pyrazolo[3,4-b]pyridines: Syntheses, reactions, and nuclear magnetic resonance spectra

Abstract

Efficient syntheses of approximately 70 simple substituted representatives of pyrazolo[3,4-Olpyridine 1 are reported from the following: ( a ) suitably substituted pyridines onto which a pyrazole ring is annelated, and (6) appropriately substituted pyrazoles onto which a pyridine ring is annelated. Selected examples of electrophilic, nucleophilic, and homolytic substitution reactions and group transformations are described, providing regiosynthetic paths to useful intermediate species. Some (26)). Our interest in synthesis and reactivity of the parent compound and its substitution products arises from promise shown as inhibitors of xanthine oxidases (27). A minor portion of our work has been reported in another study of purine analogues (28), and we have also described the synthesis of the parent system by rearrangement accompanying decarboxylation of pyrazolo[l,5-alpyrimidine carboxylic acids (29).This paper reports efficient syntheses of pyrazolo[3,4-blpyridines from (a) suitably substituted pyridines onto which a pyrazole ring is annelated, and (b) appropriately substituted pyrazoles onto which a pyridine ring is annelated. We present examples of electrophilic, nucleophilic, and homolytic substitution reactions and group transformations providing regiosynthetic paths to useful intermediate species. Aspects of substituent chemical shift influences in the 'H and 13C nr111. spectra are illustrated.

Synthesis and characterization of new 1H-pyrazolo[3,4-b]pyridine phosphoramidate derivatives

“…High resolution mass spectra (EI-70eV) were performed on a Varian MAT CH7 8500 direct inlet instrument. The Clsubstituted pyrazolo [3,4-b]pyridine (4a-c) [21][22][23][24] and aminoalkylphosphoramidates (7a-d) 25,26 compounds were prepared as previously reported.…”

Quantitative Gas‐Solid Diazotization of 3‐Aminopyrazolo[3,4‐b]pyridine Derivatives and Azo Dye Syntheses by Means of Solid‐Solid Reactions

“…[13] However, 3-diazopyrazolo[3,4-b]pyridines 2 [14] should be formulated as equilibrium mixtures with the proton at the pyrazole-N (2) and at the pyridine-N (2Ј). Semiempirical PM3 calculations predict the structure 2a to be 5 kcal·mol Ϫ1 less stable than 2aЈ.…”

Facile Three‐Component Synthesis of Macrocyclane‐Fused Pyrazolo[3,4‐b]pyridine Derivatives

“…[4,5] Nitrogen-containing heterocycles are abundant in nature and exhibit diverse and important biological properties. The pyrazolo[3,4-b]pyridine system as a key heterocycle represents the core skeleton of a pharmaceutically important class of heterocyclic compounds that possess a broad range of biological activities, [6] such as anxiolytic activity, [7] and can be used in the inhibition of xanthine oxidases [8] and cholesterol formation [9] and in the treatment of Alzheimer's disease, gastrointestinal diseases, anorexia nervosa, drug and alcohol withdrawal symptoms, drug addiction and in- [ consuming and costly syntheses, tedious work-ups and purifications of precursors as well as protection/deprotection of functional groups. This method is very efficient due to short reaction times and easy work-up and provides an efficient and promising synthetic strategy for the construction of the macrocyclane-fused pyrazolo[3,4-b]pyridine skeleton.…”