[Br:1][C:2]1[N:7]=[C:6]([CH2:8][OH:9])[CH:5]=[CH:4][C:3]=1[O:10][CH3:11]>ClCCl.O=[Mn]=O>[Br:1][C:2]1[N:7]=[C:6]([CH:8]=[O:9])[CH:5]=[CH:4][C:3]=1[O:10][CH3:11]To a solution of (6-bromo-5-methoxypyridin-2-yl)methanol (2.30 g, 10 mmol) in dichloromethane (50 mL) was added MnO2 (8.0 g) at rt. The reaction mixture was stirred at rt for 24 h. After that time the reaction was cooled to rt, filtered to remove solids and concentrated under reduced pressure to give 6-bromo-5-methoxypicolinaldehyde (1.35 g, 63%) as an off-white solid: 1H NMR (400 MHz, CDCl3): δ 9.94 (s, 1H), 7.96 (d, J=8.4 Hz, 1H), 7.27 (d, J=8.0 Hz, 1H), 4.03 (s, 3H).
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