16205-46-2

5910-12-3

The general procedure for the synthesis of 3-bromopyrazolo[1,5-a]pyridine-3-carboxylic acid from pyrazolo[1,5-a]pyridine was as follows: N-bromosuccinimide (3.06 g, 17.22 mmol) and sodium bicarbonate (4.34 g, 51.66 mmol) were sequentially added to a N,N-dimethylformamide (40 mL) solution of pyrazolo[1,5-a]pyridine-3-carboxylic acid (2.81 g, 17.22 mmol) in a solution of N,N-dimethylformamide (40 mL). The reaction mixture was stirred at room temperature for 4 h and then poured into water (100 mL). The resulting suspension was extracted twice with ethyl acetate and the organic layers were combined and dried over anhydrous magnesium sulfate. After filtration, the solvent was removed by concentration under reduced pressure. The crude product was purified by fast column chromatography (eluent: hexane/ethyl acetate = 8:2) to afford the target product 3-bromopyrazolo[1,5-a]pyridine (2.58 g, 76% yield). Mass spectrum (LRMS) showed m/z: 197 ([M+1]+). 1H-NMR (250 MHz, CDCl3) δ: 6.8 (t, 1H), 7.2 (t, 1H), 7.5 (d, 1H), 7.9 (s, 1H), 8.4 (d, 1H).