To a 250 mL round-bottomed flask was added 4-bromo-3,5-dimethylbenzaldehyde (4.0 g, 19 mmol), methanol (100 mL) and potassium iodide (623 mg, 3.8 mmol). The reaction mixture was stirred at 50 °C, followed by slow dropwise addition of tert-butyl hydroperoxide (3.9 mL, 70% aqueous solution, 28 mmol) over 30 min. After the dropwise addition, the reaction mixture was heated to reflux for 24 hours. After completion of the reaction, it was cooled to room temperature and the reaction was quenched by the addition of saturated aqueous sodium thiosulfate. The reaction mixture was extracted with ethyl acetate and the organic phase was dried with anhydrous sodium sulfate and subsequently concentrated under reduced pressure. The crude product was purified by silica gel column chromatography using petroleum ether/ethyl acetate (15:1, v/v) as eluent to afford methyl 4-bromo-3,5-dimethylbenzoate as a white solid (3.8 g, 84% yield).1H NMR (400 MHz, CDCl3) δ 7.73 (s, 2H), 3.90 (s, 3H), 2.46 (s, 6H).
