4214-76-0

2032-35-1

25045-82-3

In a 250 mL single-neck flask, bromoacetaldehyde diethyl acetal (42.5 g, 215.7 mmol) was dissolved in a mixture of 1 mol/L hydrochloric acid (120 mL) and ethanol (20 mL) and stirred at room temperature for 30 minutes. It was then heated to reflux and stirred continuously until the solution became clear. Upon completion of the reaction, the solution was cooled to room temperature and the pH was adjusted to near neutral with sodium bicarbonate solution. 2-Amino-5-nitropyridine (15.0 g, 107.8 mmol) was added and the reaction was stirred overnight at room temperature. At the end of the reaction, extraction was carried out with ethyl acetate (100 mL×3), the organic phases were combined, and the solvent was removed by concentration under reduced pressure. The crude product was purified by silica gel column chromatography (eluent ratio: petroleum ether:ethyl acetate = 2:1) to afford 13.7 g of yellow-brown crystalline 6-nitroimidazo[1,2-a]pyridine in 77.6% yield.