Step 1: Synthesis of 2-bromo-3,5-dichloropyridine
To a solution of 3,5-dichloropyridin-2-amine (1.0 g, 6.2 mmol) dissolved in 40% aqueous hydrobromic acid (8 mL), bromine (2.8 g, 17 mmol) was slowly added dropwise at -20 °C. The resulting orange-colored suspension was stirred continuously for 2 hours at -20 °C. Subsequently, aqueous sodium nitrite (1.1 g, 17 mmol) was added at the same temperature. The reaction mixture was warmed up to ambient temperature and stirring was continued for 2 hours. Upon completion of the reaction, the mixture was cooled to 0 °C and the pH was adjusted with 30% aqueous sodium hydroxide solution to about 12. The reaction mixture was extracted with ether to give a light yellow organic phase. The organic phases were combined, washed with saturated sodium chloride solution, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give the title compound 2-bromo-3,5-dichloropyridine as a yellow solid (730 mg, 52% yield).
1H NMR (400MHz, CDCl3) δ 8.27 (d, J=2.3Hz, 1H).
