2-Chloro-4-bromopyridine (5 g, 26.19 mmol, 1.0 eq.) was dissolved in 30 ml of anhydrous tetrahydrofuran and a freshly prepared lithium diisopropylammonium solution (50 ml, 28.8 mmol, 1.1 eq.) was added slowly and dropwise at -70 °C. After 1 hour of reaction, keeping the temperature at -70 °C, iodomethane (4.087 g, 28.8 mmol, 1.1 eq.) was added. After 50 min at low temperature, the reaction was quenched with saturated sodium bicarbonate solution, extracted with ethyl acetate, the organic phase was dried with anhydrous sodium sulfate and concentrated to give the solid compound 4-bromo-2-chloro-3-methylpyridine (5.22 g, yield: 97.2%).
