[Li]CCCC.N(C(C)C)C(C)C.[Br:13][C:14]1[CH:19]=[CH:18][CH:17]=[C:16]([F:20])[C:15]=1[O:21][CH3:22].[C:23](=[O:25])=[O:24]>C1COCC1.CCOCC>[Br:13][C:14]1[CH:19]=[CH:18][C:17]([C:23]([OH:25])=[O:24])=[C:16]([F:20])[C:15]=1[O:21][CH3:22]n-BuLi (17.0 mL, 42.5 mmol) was added dropwise to the solution of NH(i-Pr)2 (4.50 g, 44.5 mmol) in 70 mL of THF at −70° C. The mixture was stirred at 0° C. for 15 minutes and then cooled to −70° C. again. The solution of 1-bromo-3-fluoro-2-methoxybenzene (8.30 g, 40.5 mmol, in 30 mL of THF) was added dropwise. The resulting mixture was stirred at −70° C. for 1 hour then poured into fresh dry ice and stirred overnight. The mixture was diluted with 1 L of ether and washed with water twice. The combined water layer was washed with ether then acidified to pH=2 with hydrochloric acid and extracted with EtOAc twice. The combined EtOAc layer was washed with brine, dried over anhydrous Na2SO4 and concentrated to give 4-bromo-2-fluoro-3-methoxybenzoic acid.
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