The general procedure for the synthesis of 4-(3-trifluoromethylphenyl)benzoic acid from 4-bromobenzoic acid and 3-(trifluoromethyl)phenylboronic acid was as follows: Pd(dppf)Cl2 (1.49 mmol, 1.09 g) was added to a mixture containing 4-bromobenzoic acid (14.9 mmol, 3.0 g), 3-(trifluoromethyl)phenylboronic acid (17.9 mmol, 3.4 g), and Cs2CO3 (37.3 mmol, 12.2 g) in a suspension with the solvent being a mixture of 30 mL dioxane and 7.5 mL ethanol. The reaction mixture was stirred at 80 °C for 2 hours. After completion of the reaction, it was cooled to room temperature, the solid product was collected by filtration and washed with methanol. The filtrate was concentrated and the residue was partitioned between ethyl acetate and 1N aqueous hydrochloric acid. The organic layer was washed with saturated brine, dried over anhydrous magnesium sulfate and concentrated. To the concentrated residue was added dichloromethane, the resulting solid was collected by filtration, washed with dichloromethane and dried to give 4-(3-trifluoromethylphenyl)benzoic acid (3.58 g, 86% yield), which could be used in the next reaction without further purification.
