Tetrahydrofuran → Ethyl 4-(perfluoroethoxy)benzoate

To an oven-dried 500-mL round bottom flask equipped with a stirring bar was added 1-bromo-4-(perfluoroethoxy)benzene (9.35 g, 32.1 mmol) and anhydrous THF (200 mL). The flask was placed under nitrogen and cooled in an ice bath for 10 min. A solution of 1.3 M isopropylmagnesium chloride-lithium chloride complex (30 mL, 38.6 mmol) was added over 15 min. The ice bath was removed after 1 hour, and the reaction was warmed to room temperature and stirred overnight. GC/MS showed the presence of starting material. The reaction was cooled in an ice bath and 1.3 M isopropylmagnesium chloride-lithium chloride complex (5 mL) was added. The ice bath was removed after 20 min and stirred at room temperature for 9 hours. Ethyl chloroformate (3.4 mL, 35.3 mmol) was added in a slow, steady stream. The reaction was warmed slightly during the addition and was stirred at room temperature overnight. The reaction was diluted with EtOAc and washed with saturated aqueous ammonium chloride. The aqueous layer was extracted three times with EtOAc. The organic layers were dried over anhydrous sodium sulfate, filtered, and concentrated to give a yellow liquid, which was purified by flash chromatography (0-0, 0-4, 4-10% EtOAc/hexanes) to provide ethyl 4-(perfluoroethoxy)benzoate as a yellow liquid (4.58 g, 50%): 1H NMR (400 MHz, CDCl3) δ 8.10 (d, J=8.8 Hz, 2H), 7.28 (d, J=8.7 Hz, 2H), 4.39 (q, J=7.1 Hz, 2H), 1.40 (t, J=7.1 Hz, 3H); 19F NMR (376 MHz, CDCl3) δ −86.05, −87.84; ESIMS m/z 284 ([M+11]+).