Potassium carbonate (K2CO3, 7.6 g, 55.238 mmol) was added to a stirred solution of 3-chloro-4-hydroxybenzaldehyde (2.9 g, 18.412 mmol) in N,N-dimethylformamide (DMF, 30 mL). Iodomethane (CH3I, 7.80 g, 55.238 mmol) was added slowly and dropwise at room temperature under inert atmosphere. After the dropwise addition, the reaction mixture was heated to 80 °C and stirred continuously for 1 hour. Upon completion of the reaction, the reaction was quenched with deionized water (20 mL) and subsequently extracted with ethyl acetate (EtOAc, 2 x 50 mL). The organic phases were combined, washed sequentially with deionized water and saturated saline, dried over anhydrous sodium sulfate (Na2SO4), filtered and concentrated under reduced pressure to give the crude product. The crude product was purified by silica gel column chromatography to afford 3-chloro-4-methoxybenzaldehyde (2.78 g, 93% yield) as a yellow solid.
