Procedure for the synthesis of methyl 4-bromo-2-chloro-6-fluorobenzoate: to a mixture of compound 4-bromo-2-chloro-6-fluorobenzoic acid (20 g, 80 mmol) and potassium carbonate (13.2 g, 96 mmol) in N,N-dimethylformamide (200 mL) was added methylene iodide (23 g, 160 mmol). The reaction mixture was stirred at room temperature for 2 hours and subsequently poured into water (600 mL) and extracted with dichloromethane (2 x 200 mL). The organic layers were combined, washed sequentially with water and brine, dried over anhydrous sodium sulfate and concentrated under reduced pressure to give a brown oil. Purification by silica gel column chromatography (petroleum ether: ethyl acetate = 100:1) gave the target product methyl 4-bromo-2-chloro-6-fluorobenzoate (8 g, 49% yield, two-step reaction) as a light yellow oil.
