The general procedure for the synthesis of 5-trifluoromethylpyridine-3-boronic acid pinacol ester from pinacol ester of biphenylboronic acid and 3-bromo-5-(trifluoromethyl)pyridine was as follows: 3.50 g (15.50 mmol) of 3-bromo-5-(trifluoromethyl)pyridine, 0.54 g (0.8 mmol) of bis(triphenylphosphine)palladium(II) chloride and 4.55 g (46.5 mmol) of potassium acetate were suspended in 75 mL of dioxane and stirred for 15 minutes. Subsequently, 6.42 g (24.8 mmol) of pinacol ester of bisboronic acid (4,4,5,5,4',4',5',5'-octamethyl-[2,2']bis[[1,3,2]dioxaborolane]) was added and the mixture was heated to 100 °C for 20 hours of reaction. Upon completion of the reaction, the mixture was poured into crushed ice, the pH was adjusted to 9-10 with sodium carbonate solution, and then extracted three times with ethyl acetate. The organic phases were combined, washed with water, dried over magnesium sulfate, filtered and concentrated. The residue was purified by fast column chromatography (dichloromethane/methanol, 1:0 to 9:1) to give 3.48 g (82% yield) of 5-trifluoromethylpyridine-3-boronic acid pinacol ester as a colorless solid. Mass spectrum (MS): 273.1 (M+).
