28314-81-0

348-57-2

124-38-9

28314-81-0

(1) Synthesis of 3-bromo-2,6-difluorobenzoic acid: In a dry reaction flask, a hexane solution of 1.6 M n-butyllithium (9.4 mL, 15.0 mmol) was mixed with tetrahydrofuran (20 mL) and cooled to -78 °C. The solution was mixed with tetrahydrofuran (20 mL). To this mixed solution was sequentially added 2,2,6,6-tetramethylpiperidine (2.50 mL, 15.0 mmol) and 1-bromo-2,4-difluorobenzene (2.90 g, 15.0 mmol) and the reaction was stirred for 1 hour at -78 °C. Subsequently, crushed dry ice (5 g) was added to the reaction mixture and stirring was continued at -78 °C for 2 hours. Upon completion of the reaction, the reaction was quenched by the addition of saturated aqueous ammonium chloride solution (5 mL) and the mixture was warmed to room temperature and stirred for 30 minutes. It was diluted by adding water (10 mL) and 1 M hydrochloric acid (30 mL) and extracted with ethyl acetate. The organic phase was washed with water and dried over anhydrous magnesium sulfate. The solvent was removed by concentration under reduced pressure, hexane was added to the residue and the solid product was collected by filtration to afford 3-bromo-2,6-difluorobenzoic acid (2.30 g, 64.6% yield). The product was characterized by 1H-NMR (CDCl3): δ 6.91-6.97 (1H, m), 7.66-7.73 (1H, m).