[Synthesis]
To a 200 mL round bottom flask was added 3-[4-(dibromomethyl)-3-fluorophenyl]-1,2,4-oxadiazole (8.37 g, 25 mmol) and tetrahydrofuran (60 mL). The reaction mixture was cooled to 0 °C and diisopropylethylamine (3.48 g, 27 mmol) was added slowly and dropwise over 15 min, followed by diethyl phosphite (3.7 g, 26.8 mmol). The reaction mixture was stirred at room temperature for 60 min before the reaction was quenched with 40 mL of water. The aqueous layer was extracted with ether (2 x 80 mL). The combined organic layers were washed sequentially with 20 mL of saturated aqueous sodium bicarbonate, 20 mL of saturated aqueous ammonium chloride and 20 mL of saturated aqueous sodium chloride. The organic layer was dried with anhydrous sodium sulfate, filtered and concentrated on a rotary evaporator to obtain the crude product. The crude product was purified by short silica gel column chromatography to give 3-[4-(bromomethyl)-3-fluorophenyl]-1,2,4-oxadiazole (6.03 g, 94% yield). Melting point: 87.3°C. 1H NMR (CDCl3, 400 MHz) δ 8.80 (s, 1H), 7.94 (dd, 1H), 7.87 (dd, 1H), 7.58 (t, 1H), 4.57 (s, 2H); 13C NMR (CDCl3, 400 MHz) δ 166.97, 166.95, 165.45, 162.29, 159.73, 132.34, 132.30, 128.99, 128.90, 128.81, 124.04, 124.01, 115.56, 115.32, 25.22, 25.18; 19F NMR (CDCl3, 400 MHz) δ -115.81, -115.84, -115.86. 115.86. Elemental analysis (C9H6BrFN2O) calculated values: C, 42.05; H, 2.35; N, 10.90. measured values: C, 42.17; H, 2.17; N, 10.63. |