2,2,6,6-tetramethylhexahydropiperidine (22.5 ml, 133.4 mmol) was added to a solution of n-BuLi (26.7 ml of a 2.5 M solution in tetrahydrofuran (THF), 66.7 mmol) in THF (130 ml) at -78 C. The mixture was stirred at -78 C for 30 min and then carefully lowered to -100 C using liquid nitrogen. Pure 1-bromo-4-(trifluoromethyl)benzene (15 g, 66.7 mmol) was added. The mixture was kept at -100 C for 6 hours and poured onto freshly crushed dry ice. The resulting mixture was stirred at room temperature for 16 hours. The residual solvent was removed by evaporation. Water (150 ml) was added and the mixture was extracted (50 ml three times) with ether. The aqueous layer was acidified using concentrated hydrochloric acid (HCl) and extracted with dichloromethane (50 ml three times). The combined organic layers were washed with saturated sodium chloride (75 ml), dried over magnesium sulfate (MgSO4), filtered and concentrated to yield 2-bromo-5-trifluoromethylbenzoic acid as a white solid (5.41 g).1H NMR (300 MHz, chloroform-D) ppm 7.7 (dd, J = 8.4, 2.3 Hz, 1H) 7.9 (d, J = 8.4 Hz, 1H) 8.3 (d, J = 2.0 Hz, 1H); MS (ES+) calculated value: 267.93, measured value: 266.7 (M-1).
