Phenyl Trifluoromethyl Sulfoxide

Trifluoromethylation of an aryl halide: CuCl (74.3 mg, 0.75 mmol) and tBuOK (168 mg, 1.5 mmol) are added to a Schlenk tube. Then the Schlenk tube is sealed with a septum. DMF (2 mL) is added and stirred at room temperature for 30 min, and then 1 (189 mg, 0.975 mmol) is added at the same temperature for 30 min under an argon atmosphere. After the pregenerated “CuCF₃” species is stabilized by Et₃N·3HF (63 µL, 0.25 mmol), 1-iodo-4-nitrobenzene (125 mg, 0.5 mmol) in 0.5 mL DMF is added, and the mixture is stirred at 80 °C for 20 h. After addition of aqueous NH₃ (33%, 0.5 - 1 mL), H₂O (10 mL) and Et₂O (5 mL), the organic layer is separated and the aqueous layer is extracted with Et₂O (3 × 5 mL). The combined organic layer is washed with brine (2 × 5 mL), dried over MgSO₄, filtered and concentrated in vacuo. The residue is purified by chromatography on silica gel (pentane : dichloromethane = 5 : 1) to obtain 4-nitrobenzotrifluoride (85 mg, 89% yield) as a white solid.