Under argon protection, 6-bromopyridin-2-amine (5 g, 28.90 mmol) was dissolved in DMF (75 mL) and stirred at 0 °C. To this solution, N-bromosuccinimide (35 mg, 1.04 mmol) was slowly added. The reaction mixture was gradually warmed up to room temperature and stirred continuously for 16 hours. The progress of the reaction was monitored by TLC and after confirming complete consumption of the feedstock, the reaction was quenched with ice-cold water (50 mL). Subsequently, the reaction mixture was extracted with EtOAc (2 x 50 mL). The organic phases were combined, dried with anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The crude product was purified by column chromatography (eluent: 30% EtOAc/hexane) to afford 5,6-dibromopyridin-2-amine (6.1 g, 85% yield) as an off-white solid. The structure of the product was confirmed by 1H-NMR (CDCl3, 400 MHz) and LCMS: 1H-NMR δ 7.51 (d, 1H), 6.32 (d, 1H), 4.60 (br s, 2H); LCMS m/z 252.6 (M + 1); Chromatographic conditions: X-Select CSH C-18 column (50×3.0 mm, 3.5 μm ), mobile phase 0.05% trifluoroacetic acid aqueous solution/acetonitrile, flow rate 0.80 mL/min, retention time 3.04 min.
