Diisopropylamine (27.6 g, 273.0 mmol) was dissolved in tetrahydrofuran (300 mL) under nitrogen protection and cooled to -78 °C. A tetrahydrofuran solution of n-butyllithium (91 mL, 228.0 mmol, 2.5 M) was slowly added dropwise and stirred at -78 °C for 1 hour. Subsequently, 3-bromopyridine (30.0 g, 190.0 mmol) was added dropwise and stirring was continued at -78 °C for 20 min. Next, N,N-dimethylformamide (55.0 g, 760.0 mmol) was added dropwise and stirred at -78 °C for 1 hour. After completion of the reaction, the mixture was slowly warmed to room temperature and the reaction was quenched with saturated aqueous ammonium chloride solution (150 mL). The aqueous layer was extracted with ethyl acetate (200 mL x 3), and the organic layers were combined and concentrated in vacuum. The residue was purified by silica gel column chromatography to afford 3-bromopyridine-4-aldehyde (12.0 g, 34.0% yield). The product was confirmed by 1H NMR (400 MHz, CD3OD): δ 10.37 (s, 1H), 8.91 (s, 1H), 8.80-8.61 (m, 1H), 7.78-7.63 (m, 1H).LCMS (m/z): 187.0 (M + 1).
