Synthesis of Diaryliodonium Triflates Using Environmentally Benign Oxidizing Agents

Abstract

A range of symmetric and unsymmetric diaryliodonium triflates have been prepared employing urea-hydrogen peroxide as the oxidizing agent. The use of aqueous hydrogen peroxide and catalytic systems with methylrhenium trioxide in the oxidation of ­iodoarenes has also been investigated.

Key words

hypervalent iodine - diaryliodonium salts - oxidation - arenes - green chemistry

References and Notes

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17

Diphenyliodonium Triflate (1a): A stirred mixture of CH₂Cl₂ and TFE (2:1, 1 mL) was cooled to 0 ˚C and UHP (47 mg, 0.50 mmol) was added. Tf₂O (168 µL, 1.00 mmol) was added dropwise to the suspension and the mixture was stirred for 30 min at 0 ˚C. Iodobenzene (28 µL, 0.25 mmol) was added, followed by benzene (45 µL, 0.50 mmol) and the solution was warmed to r.t., then heated at 40 ˚C for 3 h. The mixture was allowed to cool to r.t., evaporated in vacuo and the residue was purified by trituration with Et₂O (3 × 2 mL), then dried in vacuo to afford the title compound (82 mg, 76%) as an off-white amorphous solid, spectroscopically identical with literature data.⁶
( p -Tolyl)(phenyl)iodonium Triflate (1h): Prepared according to the above procedure. The crude reaction mixture was allowed to cool to r.t., evaporated in vacuo and the residue was partitioned between CH₂Cl₂ (5 mL) and H₂O (5 mL). The aqueous layer was further extracted with CH₂Cl₂ (5 mL) and the organic extracts were combined and evaporated in vacuo. The residue was purified by trituration with Et₂O (3 × 2 mL) and dried in vacuo to afford the title compound (84 mg, 76%) as an off-white amorphous solid, spectroscopically identical with literature data.⁶