Synthesis
To an aqueous solution of 48 % strength hydrobromic acid (82 rnL) at 0 0C was added 4-chloro-2-pyridinamine (8.9 g, 69.2 mmol) followed by addition of bromine (33.4 g, 209 mmol) over 10 min. The resulting mixture was cooled to -10 0C, and a solution of NaNO2 (10.65 g, 154 mmol) in H2O (20 rnL) was poured over 30 min. The mixture was warmed at room temperature and stirred overnight. The mixture was cooled to 0 0C, and NaOH (35 %) was added until the pH >10. The mixture was then extracted with ethyl acetate. The organic layer was then dried, filtered, and concentrated in vacuo. The product was purified via column chromatography (0-20 per cent ethyl acetate/hexane) to afford 2-bromo-4-chloropyridine (12.1 g, 92 %).
