General procedure for the synthesis of 5-bromo-2-oxo-1,2-dihydropyridine-3-carbonitrile from 2-oxo-1,2-dihydropyridine-3-carbonitrile: 2-oxo-1,2-dihydropyridine-3-carbonitrile (50 mg, 0.42 mmol) and sodium acetate (69 mg, 0.84 mmol) were dissolved in 5 mL of glacial acetic acid at room temperature, and stirred until complete dissolution. Subsequently, bromine (21.5 μL, 0.42 mmol) was slowly added to the solution and the reaction lasted for 2 hours. Upon completion of the reaction, the mixture was concentrated under vacuum to remove the acetic acid. The crude product was purified by column chromatography (using ethyl acetate as eluent) to afford 5-bromo-2-oxo-1,2-dihydropyridine-3-carbonitrile (69 mg, 75% yield) as a yellow solid. Melting point: 216~217°C. 1H NMR (400MHz, CD3COCD3): δ11.70 (s, 1H), 8.22 (d, J = 2.8Hz, 1H), 8.05 (d, J = 2.8Hz, 1H).
