Pyrazolo[1,5-a]pyrimidine-5,7(4H,6H)-dione

1820-80-0

105-53-3

57489-70-0

Step A - Synthesis of pyrazolo[1,5-a]pyrimidine-5,7-diol (Int-9a): to 1H-pyrazol-3-amine (12.3 g, 148.0 mmol) in 50 mL of deionized water was added diethyl malonate (25.0 mL, 164.7 mmol), followed by the addition of an ethanolic solution of 21 wt% NaOEt (110 mL. 294.6 mmol) and additional ethanol (50 mL). The reaction mixture was heated at 80 °C for 16 h under argon protection. After completion of the reaction, it was cooled to room temperature. The reaction mixture was concentrated to near dryness under reduced pressure and 500 mL of water was added. Dissolution of the solid was promoted by vigorous stirring and the pH was subsequently adjusted to ~2 with hydrochloric acid, at which point a precipitate was generated. The precipitate was collected by vacuum filtration and dried to give pyrazolo[1,5-a]pyrimidine-5,7-diol (Int-9a) as a brown solid (17.13 g, 113.4 mmol, 77% yield).