5-oxo-4,5-dihydro-pyrazolo[1,5-a]pyrimidine-2-carboxylic acid methyl ester synthesis

Yield:1228351-47-0 29%

Reaction Conditions:

in 1,4-dioxane at 90; for 16 h;Inert atmosphere;

Steps:

3 Step-3: methyl 5-oxo-4,5-dihydropyrazolo[l,5-a]pyrimidine-2-carboxylate(A61)

To a stirred solution of methyl 3-amino-lH-pyrazole-5-carboxylate(A60, 22.0 g, 124.92 mmol) in l,4-dioxane(440 mL) was added methyl propiolate(13.30 mL, 149.90 mmol) under N₂ atmosphere and the reaction mixture was stirred at 90 °C for 16 h. After completion of reaction mixture, the solvent was concentrated to dryness. The residue was purified by column chromatography using silica gel(100-200 mesh) 0-50% EtOAc/n-Hexnes as the eluent to afford methyl 5-oxo-4,5-dihydropyrazolo[l,5-a]pyrimidine-2-carboxylate A61 as a yellow solid. Yield: 7.0 g(29%) LC-MS(ES) m/z : 194.13[M+H]⁺.

References:

WO2019/102494,2019,A1 Location in patent:Paragraph 000215