To a solution of (S)-1,1,1-trifluoro-4-(5-fluoro-2-methylphenyl)-4-methyl-2-p-tolylsulfanylmethylpentan-2-ol (31.0 g, 77.0 mmol) in 200 mL of anhydrous dichloromethane was added trimethyloxonium tetrafluoroborate (17.2 g, 116 mmol). The resulting suspension was stirred at room temperature for 4.5 hours. A solution of potassium carbonate (K2CO3, 32.1 g, 232 mmol) in 200 mL of water was then added. After 19 hours, the reaction mixture was poured into 400 mL of saturated aqueous sodium bicarbonate solution and extracted with three 400 mL portions of dichloromethane. The combined organic phases were washed with brine, dried over magnesium sulfate, filtered, and concentrated in vacuo. The crude mixture can be used in the next step without reducing the yield or can be purified by column chromatography with silica gel (eluted with 0%-2% EtOAc/hexanes) to afford (R)-2-[2-(5-fluoro-2-methylphenyl)-2-methylpropyl]-2-trifluoromethyloxirane as a clear oil (23.2 g, contains 20% methyl tolyl thioether, 87%) which was used without further purification.
