General procedure for the synthesis of methyl 3-bromo-4-(dibromomethyl)benzoate from methyl 3-bromo-4-(dibromomethyl)benzoate: To a solution of methyl 3-bromo-4-(dibromomethyl)benzoate (32.0 g, 65.3 mmol) in acetone (400 mL) was added silver nitrate (33.3 g, 196 mmol) and water (100 mL). The reaction mixture was stirred at room temperature for 1 hour away from light. Upon completion of the reaction, the resulting silver salt was removed by filtration and the filtrate was diluted with ethyl acetate and washed sequentially with brine, saturated sodium bicarbonate solution and water. The organic layer was dried over anhydrous sodium sulfate, concentrated under reduced pressure and purified by silica gel column chromatography (eluent: ethyl acetate/hexane, 0-20% gradient) to afford methyl 3-bromo-4-formylbenzoate (12.9 g, 52.0 mmol, 80% yield) as a white solid. The structure of the product was confirmed by 1H NMR (400 MHz, DMSO-d6) and LC/MS: 1H NMR δ 10.26 (s, 1H), 8.23 (s, 1H), 8.08 (d, J = 8.1 Hz, 1H), 7.97 (d, J = 8.0 Hz, 1H), 3.91 (s, 3H); LC/MS (m/z) ES: 243 ( M+1).
