2-(1-ethoxyvinyl)-3-nitropyridine (4.58 g, 23.6 mmol) was used as raw material, which was dissolved in acetic acid (46 mL), a solution of 3N hydrochloric acid (34 mL) was added, and the reaction was stirred for 9 hours at 20-25°C. Upon completion of the reaction, the reaction solution was neutralized with aqueous sodium hydroxide solution and subsequently adjusted to a weak base (pH 8-9) with aqueous sodium bicarbonate solution and extracted with ethyl acetate. The organic layer was separated, washed with saturated aqueous sodium chloride solution and dried with anhydrous sodium sulfate. The solvent was removed by distillation under reduced pressure, and the resulting residue was purified by silica gel column chromatography (eluent: hexane/ethyl acetate=2/1) to afford 1-(3-nitropyridin-2-yl)ethanone (3.08 g, yield 79%). The product was confirmed by 1H-NMR (CDCl3): δ 2.73 (3H, s), 7.60 (1H, dd, J=8.3,4.8 Hz), 8.23 (1H, dd, J=8.3,1.5 Hz), 8.83 (1H, dd, J=4.8,1.5 Hz).
