Pinacol → 3-[2-Chloro-4-(trifluoromethyl)phenoxy]benzoic acid

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To a 300 ml, 3-necked flask equipped with a condenser, stirrer, drying tube and thermometer is charged dimethylsulfoxide (100 ml), anhydrous potassium carbonate (30 g. >0.20 mole), 3,4-dichlorobenzotrifluoride (21.5 g., 0.10 mole), pinacol (10 g.) and 3-hydroxybenzoic acid (13.8 g., 0.10 mole). The reaction temperature is then taken slowly to 140°-5° C. while stirring vigorously and maintained as such for 4 days. The reaction mixture is then cooled to room temperature and the inorganic solids removed by filtration prior to pouring the filtrate into water (1200 ml). The aqueous solution is then triturated with CCl4 (2 × 200 ml), decanted and then acidified to pH1 (conc. HCl) to give a tan colored solid, 25,6 g., mp 114°-17° C. This solid is further purified by dissolving in CCl4 (500 ml) and drying with anhydrous MgSO4. The CCl4 solution is reduced in vacuo to give 19.6 g. (62%) of a yellow solid, mp 116°-19° C. Recrystallization of the yellow solid from hexane gives a tan colored solid, 3-(2-chloro-4-trifluoromethylphenoxy)-benzoic acid, mp 122°-3° C.

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