[Br:1][C:2]1[N:7]=[C:6]([O:8]C)[C:5]([NH2:10])=[CH:4][CH:3]=1>C(O)(=O)C.Br>[NH2:10][C:5]1[C:6](=[O:8])[NH:7][C:2]([Br:1])=[CH:3][CH:4]=1A solution of 6-bromo-2-methoxy-pyridin-3-ylamine (1A) (5.2 g, 25.6 mmol) in acetic acid (50 mL) and HBr (50 mL) is heated to reflux with an oil bath at 120° C. for 1 hour. The reaction solution is cooled to room temperature and concentrated to dryness. The crude product is purified by chromatography (CH2Cl2 95%, MeOH 5%) to give 3-amino-6-bromo-1H-pyridin-2-one (1B) (3.5 g, yield 72%) as brown solid that turns to deep purple. MS (ESI) m/e 189, 191 (M+H+).
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