IMidazo[1,2-a]pyridine-3-carboxylic acid, 6-broMo-, ethyl ester

1072-97-5

1004550-24-6

372198-69-1

General procedure for the synthesis of ethyl 6-bromoimidazo[1,2-A]pyridine-3-carboxylate from 2-amino-5-bromopyridine and 2-chloro-3-oxopropanoic acid ethyl ester potassium salt: In a sealed tube, 2-amino-5-bromopyridine (5.92 g, 34.2 mmol) and 2-chloro-3-oxopropanoic acid ethyl salt potassium salt (20.0 g, 106.0 mmol) were added to a solution of ethanol (140 mL) containing concentrated sulfuric acid (2.7 mL) in a solution of ethanol (140 mL). The reaction vessel was sealed by purging with nitrogen and the reaction was heated at 90 °C for 18 hours. Upon completion of the reaction, the resulting slurry was cooled to room temperature, filtered and concentrated under reduced pressure. The residue was diluted with ethyl acetate and washed sequentially with 1N sodium hydroxide solution and brine. The combined aqueous layers were back-extracted with a 95:5 solvent mixture of ethyl acetate/methanol. The combined organic extracts were dried with anhydrous sodium sulfate and filtered through a diatomaceous earth pad after decolorization with the addition of activated carbon. The filtrate was concentrated under reduced pressure and the residue was recrystallized with a 1:1 ethyl acetate/hexane solvent mixture (100 mL) to give 5.09 g (55% yield) of the target product, ethyl 6-bromoimidazo[1,2-A]pyridine-3-carboxylate, as an off-white solid. Mass spectrum (electrospray ionization) showed m/e 271.2 [M+H]+.