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0 °C

To a stirred solution of 4-bromo-2-fluorobenzoic acid (60 g, 274 mmol) in anhydrous THF (700 mL) at 0° C. was added DMF (2 mL) followed by oxalyl chloride (48 mL, 548 mmol) portionwise over 1 hour. The mixture was stirred at 0° C. for 30 min, and then at room temperature for 1 hour. The solvent was removed under reduced pressure, and the residue dissolved in DCM (700 mL). tert-Butyl alcohol (97 g, 1315 mmol) and pyridine (150 mL) were added, and the reaction mixture was stirred at room temperature for 64 h. The mixture was transferred to a separating funnel and washed with water (400 mL), 2 N NaOH aqueous solution (400 mL) and brine (2×200 mL), dried over magnesium sulfate, filtered and concentrated under vacuum. The residue was purified by flash chromatography on silica gel (0 to 5% ethyl acetate in heptane over 30 min) to give tert-butyl 4-bromo-2-fluorobenzoate (60 g, 80%) as an oil. LCMS (m/z): 218/220 (MH+ (−tBu)), 1.11 min; 1H NMR (500 MHz, CDCl3) δ ppm 7.81-7.71 (m, 1H) 7.39-7.30 (m, 2H) 7.29 (s, 1H) 1.68-1.55 (m, 9H).

1. waitat room temperature for 1 hour
2. customThe solvent was removed under reduced pressure
3. dissolutionthe residue dissolved in DCM (700 mL)
4. stirringthe reaction mixture was stirred at room temperature for 64 h
5. customThe mixture was transferred to a separating funnel
6. washwashed with water (400 mL), 2 N NaOH aqueous solution (400 mL) and brine (2×200 mL)
7. dry with materialdried over magnesium sulfate
8. filtrationfiltered
9. concentrationconcentrated under vacuum
10. customThe residue was purified by flash chromatography on silica gel (0 to 5% ethyl acetate in heptane over 30 min)