5-Bromo-pyrazolo[1,5-a]pyridine-3-carboxylic acid ethyl ester

Synthesis

1533440-88-8

623-47-2

885276-93-7

General procedure for the synthesis of ethyl 5-bromopyrazolo[1,5-a]pyridine-3-carboxylate from 1-amino-4-bromopyridinium iodide and ethyl propargylate: To a 250 mL three-necked round-bottomed flask was added 1-amino-4-bromopyridinium iodide (Compound 64.2, 15 g, ca. 50% purity, 24.9 mmol) in N,N-dimethylformamide (80 mL) Solution. Potassium carbonate (10.6 g, 76.7 mmol) was added batchwise, followed by ethyl propargylate (11.7 mL, 115 mmol) dropwise over 10 min. The reaction mixture was stirred overnight at room temperature and then diluted with ethyl acetate (300 mL) and water (100 mL). Insoluble solids were removed by filtration, and the organic layer was washed with saturated saline (3 x 50 mL), dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by silica gel column chromatography using ethyl acetate/petroleum ether (1:10) as eluent to afford ethyl 5-bromopyrazolo[1,5-a]pyridine-3-carboxylate as a brown solid (300 mg, 6% yield).

References