3-Bromo-5-methoxypyridine (100 mg, 0.53 mmol) was placed in an oven-dried round-bottomed flask equipped with a magnetic stir bar and dissolved in anhydrous tetrahydrofuran (1 mL). Subsequently, isopropylmagnesium chloride (0.3 mL) was added at 0 °C and the resulting mixture was stirred at room temperature for 2 h (the solution turned light brown). Then, anhydrous tetrahydrofuran (0.1 mL) solution of N,N-dimethylformamide (0.1 mL) was slowly added. The initially formed solid gradually dissolved and the color of the solution changed from light brown to light yellow. after 1 h, the reaction mixture was cooled to 0 °C and the reaction was quenched with deionized water (2 mL). The organic layer was separated and the aqueous layer was further extracted with dichloromethane (3 x 3 mL). The organic layers were combined and dried over anhydrous sodium sulfate and subsequently concentrated in vacuum on a rotary evaporator. The crude product was purified by gradient silica gel column chromatography with the eluent being a solvent mixture of hexane and ethyl acetate (ratio from 20:1 to 1:1) to afford the target product 5-methoxy-pyridine-3-carbaldehyde as a colorless slurry (45 mg, 63% yield).1H NMR (500 MHz, CDCl3): δ 10.09 (s, 1H), 8.65 (d, J = 0.9 Hz, 1H), 8.54 (d, J = 3.1 Hz, 1H), 7.60 (dd, J = 5.1, 1.5 Hz, 1H).13C NMR (125 MHz, CDCl3): δ 190.6, 156.2, 145.1, 144.8, 132.0, 116.3, 55.7.
