To a solution of 5-bromo-3-chloro-N-methoxy-N-methylpyridinamide (9.0 g, 32.3 mmol, 1.0 equiv) in tetrahydrofuran (THF, 100 mL) was slowly added lithium aluminum hydride (LAH, 1 M in THF, 16.12 mL, 16.1 mmol, 0.5 equiv) at -70 °C. The reaction was continued at this temperature for 2 hours. Upon completion of the reaction (monitored by thin layer chromatography TLC), the reaction mixture was quenched with saturated sodium bicarbonate (NaHCO3) solution. Subsequently, it was extracted with ethyl acetate (EtOAc, 3 x 250 mL), the organic layers were combined and washed sequentially with distilled water (500 mL) and saturated saline (500 mL). The organic layer was dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by rapid column chromatography (CC) to afford 5-bromo-3-chloropyridin-2-aldehyde (5.0 g, 71% yield) as a brown gel.
