Synthesis of 6‐(2‐hydroxybenzoyl)pyrazolo[1,5‐a]pyrimidines by reaction of 5‐amino‐1h‐pyrazoles and 3‐formylchromone

Abstract

Reaction of 3-formylchromone (1) with 5-amino-1H-pyrazoles (2) in ethanol, afforded 6-(2-hydroxybenzoyl)pyrazolo[1,5-a]pyrimidines (3a-g) in good yields. The structures and the regiospecificity of the reaction were established by nmr measurements and X-ray analysis, in which soft intermolecular hydrogenbonded networks were found.

Chemistry and application of 4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde

“…5-Aminopyrazole 166 (R = alkyl, aryl), however, behaves differently from the aforesaid two aminobenzopyrans; it undergoes through its exocyclic and endocyclic nucleophilic nitrogens a [3+3]cyclization with 1 with concomitant opening of the pyran ring to afford the pyrazolo[1,5-a]pyrimidine 167 [147]. The initially formed Michael adduct of the chromone based dienamine 163 with 1 reorganizes to the xanthone 90 (R = CHO) [148].…”

Transformation of 4‐oxo‐4H‐[1]‐benzopyran‐3‐carboxaldehydes into pyrazolo[3,4‐B]pyridines

“…Unlike 5-amino-3-methyl-1-phenylpyrazole, 5-amino-3-methyl-1H-pyrazole reacts with 3-formylchromones in ethanol affording 6-(2-hydroxybenzoyl)pyrazolo[1,5-a]-pyrimidines. No pyrazolo [3,4-b]pyridines were isolated in that case [17]. Introduction of a substituent on the N-1 atom of pyrazole ring prevents formation of tautomers and changes its reactivity towards 3-formylchromone.…”

Synthesis, Antiviral, and Antimicrobial Evaluation of Benzyl Protected Diversified C-nucleosides

“…Pyrazoles constitute an important class of compounds in organic synthesis due to two nitrogen groups being part of the molecule. In addition, pyrazolo-pyrimidines are considered as one of the most useful synthetic intermediate to synthesize variety of molecules and possible drug candidates (Hocková et al, 1999; Quiroga et al, 2009). Since many years, hydrazide derivatives have been the focus of interest for many synthetic chemists and biologists because of the synthetic importance and the biological activity associated with them.…”