To a hexane solution of 0.5 M n-butyllithium (1.7 mL, 2.4 mmol) was added slowly and dropwise a tetrahydrofuran (THF, 10 mL) solution of 5-bromo-2-trifluoromethylpyrimidine (700.6 mg, 3.1 mmol) and triisopropyl borate (1.1 mL, 4.7 mmol) at -78°C. The reaction mixture was stirred continuously at -78 °C for 2 h. The reaction was subsequently quenched with water. The solvent was removed by distillation under reduced pressure and the residue was extracted with ether (2 x 40 mL). After separation of the aqueous layer, the pH was adjusted to 6 with 1N hydrochloric acid and extracted with ethyl acetate (EA, 3 x 40 mL). The organic layers were combined, washed with saturated saline, dried over anhydrous sodium sulfate, and concentrated to obtain the target product 2-(trifluoromethyl)pyrimidin-5-ylboronic acid (400 mg, 67.2% yield) as a white solid. Liquid chromatography-mass spectrometry (LC-MS) analysis showed a retention time of 0.66 min and a molecular ion peak (MH+) of 193.
