PYRAZOLO[1,5-A]PYRIMIDINE-3-CARBOXYLIC ACID

115932-00-8

25940-35-6

The general procedure for the synthesis of pyrazolo[1,5-a]pyrimidine-3-carboxylic acid from ethyl pyrazolo[1,5-a]pyrimidine-3-carboxylate was as follows: to a mixture of ethyl pyrazolo[1,5-a]pyrimidine-3-carboxylate (3.15 g, 16.4 mmol) in ethanol (50 mL) and water (40 mL) was added an aqueous solution of 2 M potassium hydroxide (40 mL). The reaction mixture was stirred at 50 °C for 2 h, subsequently cooled to room temperature and concentrated under vacuum. The resulting mixture was adjusted to pH=2 with 1 M aqueous hydrochloric acid, at which time a white solid precipitated. The white solid product was collected by filtration to give 2.6 g (97% yield). The product was detected by LC-MS (ESI, negative ion mode), m/z: 162.1 [M-H]-. 1H NMR (600 MHz, DMSO-d6) δ (ppm): 9.26 (dd, J=7.0,1.7 Hz, 1H), 8.80 (dd, J=4.1,1.7 Hz, 1H), 8.58 (s, 1H), 7.26 ( dd, J=7.0,4.1 Hz, 1H).