Ammonium Chloride → Ethyl 5-chloro-1H-pyrrolo[3,2-b]pyridine-2-carboxylate

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Reaction Steps

To a solution of 3-(2-chloro-5-nitropyridin-6-yl)-2-oxopropionic acid ethyl ester (Preparation 3, 1.53 g, 5.6 mmol) in THF (65 mL) and ethanol (30 mL) was added saturated aqueous ammonium chloride solution (30 mL) and the suspension was vigorously stirred at rt. Iron powder (1.95 g, 34.8 mmol) was added portionwise and the mixture was heated under reflux for 2 h then allowed to cool prior to filtration through a celite plug, and washed with warm THF. The mixture was concentrated under reduced pressure to give an aqueous suspension, which was filtered through a sinter, washing with water. The wet solid was washed with methanol and dried. The residue was adsorbed onto silica gel and purified via flash chromatography eluting with ethyl acetate/hexane (1:19) to give the title compound. δH (CD3OD): 1.42 (3H, t), 4.42 (2H, q), 7.15 (1H, s), 7.30 (1H, d), 7.89 (1H, d); m/z (ES+)=225.03 [M+H]+, RT=3.32 min.

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