Synthesis
To a 500 mL three-necked flask equipped with a thermometer was added N,N-dimethylformamide (DMF, 200 mL), m-trifluoromethylphenol (0.26 mol, 42.2 g), potassium carbonate (0.266 mol, 37.2 g) and 6-chloro-pyridine-2-carboxylic acid (0.2 mol) were added sequentially. Subsequently cuprous chloride (1.0 g) was added and the reaction mixture was heated to 140 °C and kept at this temperature for 6.0 hours. Upon completion of the reaction, the mixture was cooled to room temperature and then the reaction solution was slowly poured into 600 mL of ice water. The pH of the mixture was adjusted with concentrated hydrochloric acid to 3. The precipitate precipitated was collected by filtration, washed with water several times, and dried to give 6-(3-trifluoromethylphenoxy)-2-pyridinecarboxylic acid as a white solid in 75% yield.