[Li]CCCC.C(NC(C)C)(C)C.[Br:13][C:14]1[CH:19]=[C:18]([F:20])[CH:17]=[C:16]([Br:21])[CH:15]=1.[C:22](=[O:24])=[O:23]>C1COCC1.CCOCC>[Br:13][C:14]1[CH:15]=[C:16]([Br:21])[CH:17]=[C:18]([F:20])[C:19]=1[C:22]([OH:24])=[O:23]A solution of n-BuLi (20 mL, 50.0 mmol) was added dropwise to a solution of diisopropylamine (5.6 g, 55.0 mmol) in 200 mL of THF at −70° C. The mixture was stirred at 0° C. for 15 minutes and then recooled to −70° C. A solution of 1,3-dibromo-5-fluorobenzene (12.7 g, 50.0 mmol, in 50 mL of THF) was added dropwise. The resulting mixture was stirred at −70° C. for 2 hours 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 2,4-dibromo-6-fluorobenzoic acid as white solid.
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