Toluene → 5-Bromo-2-(2,3-difluoro-4-methoxyphenoxy)benzoic acid

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To a 500 mL flask charged with 2,5-dibromobenzoic acid (14 g, 50.0 mmol) and copper (I) trifluoromethanesulfonate toluene complex (1.29 g, 2.50 mmol) were added toluene (100 mL, 50.0 mmol) followed by EtOAc (0.25 mL, 2.50 mmol) and 2,3-difluoro-4-methoxyphenol (8.41 g, 52.5 mmol). To the resulting green mixture was added cesium carbonate (34.2 g, 105 mmol) in two portions. The mixture was stirred at rt for 5 minutes before being placed in a 110° C. oil bath where it was maintained for 12 h. The reaction was cooled to rt and poured into a separatory funnel containing 1 L of water. The layers were separated and the aqeuous layer was washed with ethyl acetate (2×200 mL). The aqeuous layer was acidified with 6 N HCl and extracted with ethyl acetate (3×500 mL). The combined organic layers were washed with brine, dried over sodium sulfate, filtered and concentrated to provide a brown oil. The derived oil was triturated with ethyl acetate (100 mL) and hexanes (1000 mL). The slurry was cooled to −10° C. for 4 hours then filtered to provide 5-bromo-2-(2,3-difluoro-4-methoxyphenoxy)benzoic acid (11.55 g, 32.2 mmol, 64.3% yield) as a light tan solid.

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