Step 1: 2-Amino-3-fluoro-5-chloropyridine (5.0 g, 34 mmol) was slowly added to 48% hydrobromic acid (HBr) solution (20 mL) at 0°C with stirring. Bromine (Br2, 5.24 mL, 102.3 mmol) was then added dropwise to the resulting mixture over 20 min at 0 °C. The reaction mixture was cooled to -10°C. A solution of sodium nitrite (NaNO2, 5.88 g, 85.3 mmol) in water (20 mL) was slowly added to the mixture over a period of 1.5 h and the mixture continued to be stirred for 30 min. Subsequently, a solution of sodium hydroxide (NaOH, 12 g, 306 mmol) in water (20 mL) was added over 30 minutes and the mixture was gradually warmed to room temperature. After completion of the reaction, the mixture was extracted with ether (3 x 100 mL). The combined organic phases were washed with saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated to give the title compound 2-bromo-5-chloro-3-fluoropyridine as a pale yellow solid (6.43 g, 90% yield). The product was characterized by 1H NMR (400 MHz, CDCl3): δ 8.23 (d, J = 2.1 Hz, 1H), 7.48 (dd, J = 7.1,2.1 Hz, 1H).
