PhI-Catalyzed α-Tosyloxylation of Ketones with m-Chloroperbenzoic Acid and p-Toluenesulfonic Acid

Abstract

Various α-tosyloxyketones were efficiently prepared in high yields from the reaction of ketones with m-chloroperbenzoic acid and p-toluenesulfonic acid in the presence of a catalytic amount of iodobenzene at warming temperature.

Key words

iodobenzene - α-tosyloxyketones - ketones - m-chloro­perbenzoic acid - p-toluenesulfonic acid - catalysts

References and Notes

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6

Typical Procedure for PhI-Catalyzed α-Tosyloxylation of Ketones with MCPBA and PTSA
To a solution of acetophenone (120 mg, 1 mmol) in MeCN (5 mL) were added iodobenzene (20 mg, 0.1 mmol), PTSA monohydrate (209 mg, 1.1 mmol) and MCPBA (65% purity, 292 mg, 1.1 mmol). The mixture was stirred for 5 h at 50 °C under an Ar atmosphere. After the reaction, the reaction mixture was poured into sat. aq NaHCO₃ solution and extracted with CHCl₃ (3 × 30 mL). The organic layer was dried over Na₂SO₄. After removal of the solvent under reduced pressure, α-tosyloxyacetophenone was obtained in an almost pure state. If necessary, the residue was purified by short column chromatography (eluent: hexane-EtOAc, 3:1) to give pure α-tosyloxyacetophenone in 85% (247 mg) yield.
α-Tosyloxyacetophenone Mp 90 °C (lit. [10] mp 90-91 °C). IR (KBr): 1715, 1360, 1180 cm^-1. ¹H NMR (400 MHz, CDCl₃): δ = 2.45 (s, 3 H), 5.27 (s, 2 H), 7.35 (d, J = 8.5 Hz, 2 H), 7.47 (t, J = 8.2 Hz, 2 H), 7.61 (t, J = 8.2 Hz, 1 H), 7.85 (m, 4 H).
Other α-tosyloxyketones were also identified by comparison with previously prepared authentic compounds. [4d]