Hydrogen Peroxide → Pyridine, 4-[4-fluoro-3-(trifluoromethyl)phenyl]-, 1-oxide

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Reaction Steps

Then, 4-(4-fluoro-3-trifluoromethyl-phenyl)-pyridine-1-oxide 74 was prepared as follows. To a solution of compound 73 (2.49 g, 10.3 mmol) in dichloromethane (10 mL) was added methyltrioxorhenium(VII) (0.128 g, 0.515 mmol), followed by hydrogen peroxide in water (30%, 5.15 mL). The reaction mixture was stirred at room temperature for 16 hours. Manganese (IV) oxide (0.050 g) was added. The mixture was stirred for another 30 minutes. The organic layer was separated. The aqueous layer was extracted with more dichloromethane (2×10 mL). The combined organic phase was washed with brine (3×30 mL), dried over MgSO4 and filtered. After evaporating the solvent, the crude material was loaded to a silica gel column, eluting with 10% methanol in ethyl acetate to give a white solid 74 (2.51 g, 94%). 1H-NMR (CDCl3, 400 MHz) δ 7.35 (t, J=9.3 Hz, 1H), 7.49 (d, J=7.2 Hz, 2H), 7.74–7.82 (m, 2H), 8.30 (d, J=7.1 Hz, 2H); MS (DCI) m/z 258, 259 (M+H)+.

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