Diisopropylethylamine → 3-(4-(Bromomethyl)-3-fluorophenyl)-1,2,4-oxadiazole

Participants

Reaction Conditions

Reaction Steps

To a stirring mixture of 3-(3-fluoro-4-methylphenyl)-1,2,4-oxadiazole (5.34 g, 30 mmol), CCl4 (50 mL) and NBS (11.7 g, 66 mmol) was added AIBN (246 mg, 1.5 mmol). The reaction mixture was heated to 80° C. for 3 hour under nitrogen, cooled to room temperature, and 50 mL of saturated sodium bicarbonate solution was added. The organic layer was separated and the aqueous layer was extracted with dichloromethane (50 mL). The organic layer was dried over sodium sulfate, filtered and concentrated on a rotovap to give 3-(4-(dibromomethyl)-3-fluorophenyl)-1,2,4-oxadiazole, (9.34 g, 93%) as a white solid which was used in the next step without further purification. A 200 mL round bottom flask was charged with 3-(4-(dibromomethyl)-3-fluorophenyl)-1,2,4-oxadiazole (8.37 g, 25 mmol) and THF (60 mL). The mixture was cooled to 0° C. and diisopropyl ethyl amine (3.48 g, 27 mmol) was added dropwise over 15 minutes, followed by diethyl phosphite (3.7 g, 26.8 mmol). The mixture was stirred at room temperature for 60 minutes and quenched with 40 mL of water. The aqueous layer was extracted with ether (2×80 mL). The combined organic layer was washed with 20 mL of sat aq. NH4Cl and 20 mL of saturated sodium chloride solution. The organic layer was dried over sodium sulfate, filtered and concentrated on a rotovap to give a crude solid which was purified by a short silica pad to afford 3-(4-(bromomethyl)-3-fluorophenyl)-1,2,4-oxadiazole (6.03 g, 94%). mp 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. Anal. Calcd for C9H6BrFN2O: C, 42.05; H, 2.35; N, 10.90. Found: C, 42.17; H, 2.17; N, 10.63.

Provenance & Evidence