A solution of lithium diisopropylammonium (LDA, 2M, 8.5 mL) was added slowly and dropwise to a solution of 4-bromo-2-fluoropyridine (2 g, 11.3 mmol) in tetrahydrofuran (THF, 40 mL) at -78 °C. The reaction mixture was stirred continuously at -78 °C for 1 h, followed by dropwise addition of iodomethane (4.8 g, 34 mmol). After continued stirring at -78 °C for 1 h, the reaction mixture was allowed to slowly warm up to room temperature over a period of 1 h. The reaction was completed with the addition of iodomethane (4.8 g, 34 mmol). Upon completion of the reaction, the reaction was quenched with saturated sodium bicarbonate (NaHCO3) solution, followed by the addition of an aqueous solution of ammonium chloride (NH4Cl, 50 mL) at 0 °C and extraction with ethyl acetate (EA, 60 mL x 3). The organic layers were combined, washed with brine (60 mL), dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure. The residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate, PE/EtOAc) to afford 2-fluoro-3-methyl-4-bromopyridine (1 g, 47% yield) as a yellow solid.1H-NMR (400 MHz, CDCl3) δppm: 2.35 (s, 3H), 7.36 (d, 1H), 7.86 (d, 1H).
