55405-64-6

7440-66-6

232600-78-1

b) Preparation of pyrazolo[1,5-a]pyrimidin-3-ylamine hydrochloride In a 250 mL three-necked round-bottomed flask equipped with a magnetic stirrer, condenser and thermometer, 100 mL of ethanol, 12 mL of water, 3.3 g of ammonium chloride and 10 g of 3-nitropyrazolo[1,5-a]pyrimidine were added. The mixture was heated to reflux. After the heating was stopped, 16 g of zinc powder was added in batches to maintain the reflux state. After the zinc powder was added, the heating was continued to reflux for 3 hours. Upon completion of the reaction, the mixture was filtered while hot to remove the zinc salt. The filtrate was cooled until crystals precipitated. The crystalline product was collected by filtration and dissolved in 100 mL of anhydrous ethanol. Gaseous hydrochloric acid was passed into the ethanol solution, followed by the addition of 1 L of diisopropyl ether to precipitate the hydrochloride salt. The precipitate was collected and dried over phosphoric anhydride under vacuum to give 6 g of pyrazolo[1,5-a]pyrimidin-3-amine hydrochloride (red solid) in 57.5% yield. 1H NMR (D2O; 200 MHz): δ 7.18 (dxd; J1 = 4.2 Hz, J2 = 7.1 Hz; 1H); 8.33 (s; 1H); 8.65 (dxd; J1 = 4.2 Hz, J3 = 1.6 Hz; 1H); 8.90 (dxd; J2 = 7.1 Hz, J3 = 1.6 Hz; 1H).