102-52-3

6825-71-4

1260169-02-5

Ethyl 3,5-diamino-1H-pyrazole-4-carboxylate (5.00 g, 29.38 mmol) and 1,1,3,3-tetramethoxypropane (14.50 mL, 88.15 mmol) were reacted in DMF (80 mL). AcOH (0.34 mL, 5.88 mmol) was added as a catalyst. The reaction mixture was stirred at 100 °C for 14 hours. After completion of the reaction, the solvent was removed by vacuum concentration. The residue was partitioned between DCM (50 mL) and water (50 mL) to separate the organic phase. The aqueous phase was extracted with DCM (100 mL x 3). The organic phases were combined, washed with brine (100 mL), dried over anhydrous Na2SO4, filtered and concentrated in vacuum. The residue was purified by silica gel column chromatography (eluent: NH3 solution in MeOH (7 M)/DCM (v/v) = 1/100) to afford ethyl 2-aminopyrazolo[1,5-a]pyrimidine-3-carboxylate as a light yellow solid (3.52 g, 58.1% yield).MS (ESI, cation) m/z: 207.1 [M+H]+; 1H NMR (400 MHz, CDCl3): δ (ppm) 8.60 (dd, J=4.40 Hz, 1.76 Hz, 1H), 8.46 (dd, J=6.76 Hz, 1.76 Hz, 1H), 6.86 (dd, J=6.72 Hz, 4.40 Hz, 1H), 4.50 (q, J=7.08 Hz, 2H), and 1.47 (t, J=7.08Hz, 3H).