2-Amino-3,5-dibromo-4-methylpyridine

Synthesis

695-34-1

3430-29-3

a) Preparation of 2-amino-3,5-dibromo-4-methylpyridine: 2-amino-4-methylpyridine (30.0 g, 0.277 mol) was dissolved in 72% sulfuric acid (130 mL) and cooled to 0°C in an ice bath. Bromine (21.5 mL, 0.416 mol) was added slowly dropwise with stirring, and the rate of dropwise acceleration was controlled to keep the reaction temperature at 0 °C. After the dropwise addition, the reaction mixture was gradually warmed to 25 °C and the reaction was stirred at this temperature for 18 hours. Upon completion of the reaction, the reaction solution was slowly poured into ice water and the pH was adjusted with 50% sodium hydroxide solution to 10. At this point, the target product 2-amino-3,5-dibromo-4-methylpyridine precipitated as a solid, which was collected by filtration. The filtrate was extracted with dichloromethane, the organic layers were combined and dried over anhydrous magnesium sulfate. The dried organic phase was concentrated and the resulting solid was combined with the solid obtained by previous filtration and further purified by fast column chromatography (eluent: 2% methanol/dichloromethane) to give the final white solid product 2-amino-3,5-dibromo-4-methylpyridine (42.7 g, 58% yield). The structure of the product was confirmed by 1H NMR (CDCl3): δ 8.08 (s, 1H), 4.95 (bs, 2H), 2.51 (s, 3H).

References