Hypervalent Iodine-Mediated Beckmann Rearrangement of Ketoximes

Abstract

We developed a Beckmann rearrangement employing hypervalent iodine reagent under mild conditions. The reaction of ketoxime with hypervalent iodine afforded the corresponding ketone, but premixing of hypervalent iodine and a Lewis acid was effective for promoting Beckmann rearrangement. Aromatic and aliphatic ketoximes were converted into their corresponding amides in good to high yields.

Key words

hypervalent iodine reagent - Beckmann rearrangement - oxime - amide - Lewis acid

• References and Notes


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• 9 The experimental Procedures and Characterization Data The solution of PhI(OAc)₂ (0.48 mmol) and BF₃·Et₂O (0.96 mmol) in CH₃CN (1.0 mL) was stirred at 70 °C for 30 min. Then p-methoxyacetophenone (1a, 0.40 mmol) was added to the above mixture and stirred 70 °C for 5 min. Cooling to r.t., 0.5% aq Na₂SO₃ was added to the reaction mixture and extracted with CHCl₃. Combined organic layer was washed with water, dried over Na₂SO₄, and concentrated in vacuo. The residue was purified by SiO₂ column chromatography (n-hexane/AcOEt = 1:1) and preparative TLC (n-hexane/AcOEt = 5:1) to give N-(4-methoxyphenyl)acetamide (2a, 97%) as white solid. N-(4-Methoxyphenyl)acetamide (2a) White solid. ¹H NMR (CDCl₃): δ= 2.14 (3 H, s), 3.78 (3 H, s), 6.85 (2 H, d, J = 8.8 Hz), 7.28 (1 H, br), 7.38 (2 H, d, J = 8.8 Hz). ¹³C NMR (CDCl₃): δ = 24.1, 55.4, 113.9, 122.0, 131.1, 156.3, 168.7.