26911-66-0Relevant articles and documents
Synthesis of N- and C-azolyl-substituted pyrazolo[1,5-a]pyrimidines by recyclization of pyrimidinium salts
Danagulyan, Gevorg G.,Tumanyan, Araksya K.,Attaryan, Oganes S.,Tamazyan, Rafael A.,Danagulyan, Anna G.,Ayvazyan, Armen G.
, p. 483 - 490 (2015/10/19)
We studied the reaction of 2-(ethoxycarbonyl)methyl-1,4,6-trimethylpyrimidinium iodide with hydrazides of N-azolyl- and C-pyrazolyl-substituted carboxylic acids, which were synthesized by reacting the respective esters with hydrazine hydrate. This reaction was shown to result in recyclization and formation of ethyl 2-(pyrazolylalkyl)- and 2-(azolylalkyl)-5,7-dimethylpyrazolo[1,5-a]pyrimidine- 3-carboxylates. Besides pyrazolopyrimidines, the separation of reaction mixture provided in some cases also another recyclization product, 2-hydroxy-5,7-dimethylpyrazolo[1,5-a]pyrimidine.
STUDIES IN THE FIELD OF NITROGEN HETEROCYCLIC COMPOUNDS. PART XIV. SYNTHESIS OF PYRAZOLOPYRIDINE AND PYRAZOLOPYRIMIDINE DERIVATIVES
Balicki, Roman
, p. 1251 - 1261 (2007/10/02)
The reactions of various β-dicarbonyl compounds, β-diketones (1a-1g), β-ketoaldehydes (1h-1j) and β-ketoesters (1k-1w) with 3-amino-5-pyrazolone (2) in acetic acid solution were examined.On the basis of the experimental data obtained, a general scheme of this reaction was proposed.In the first, reversible step of the reaction, the intermediates (A, B, C) can be formed as a result of a competitive attack of three possible nucleophilic centers of 2 (C-4, N-1, -NH2) on a more positive carbonyl carbon atom of compound 1.Subsequent intermolecular cyclization of intermediates affords the corresponding pyrazolopyridines (3) and/or pyrazolopyrimidines (4, 6).It was found that the direction of cyclocondensation was noticeably affected by the nature of the dicarbonyl precursor, as well as the charge distribution and relative nucleophility of active centers of pyrazole ring within individual intermediates.
