Oxidation of Alcohols and Pyridines by a Water-Soluble Polyoxometalate with Hydrogen Peroxide

Abstract

A water-soluble catalyst based on a silicotungstate polyoxometalate, K₈[β-SiW₁₁O₃₉] · 14H₂O, was developed for the oxidation of pyridines and alcohols with hydrogen peroxide. The reactions were carried out in water, and good yields of the corresponding heterocyclic N-oxides and ketones were obtained under relatively mild conditions. The catalyst could be easily recovered by extraction with ethyl acetate and reused several times.

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GRAPHICAL ABSTRACT

Keywords:

• Alcohols
• oxidation
• polyoxometalate
• pyridines

ACKNOWLEDGMENT

This work was financially supported by the National Natural Science Foundation of China (Grant No. 20803032).

Notes

^b

^a Reaction conditions: catalyst 9.3 µmol, water 1 mL, cyclohexanol 1 mmol, hydrogen peroxide 5 mmol, reaction temperature 90 °C, reaction time 7 h.

^b Na₂SiO₃ · 9H₂O 9.3 µmol, Na₂WO₄ · 2H₂O 9.3 µmol.

^a Reaction conditions: K₈[β-SiW₁₁O₃₉] · 14H₂O 9.3 µmol, water 1 mL, substrate 1 mmol, hydrogen peroxide 5 mmol, reaction temperature 90 °C, reaction time 7 h.

^b 20 µmol of methyltrioctylammonium chloride was added.

^c By-product was benzaldehyde.

^a Reaction conditions: K₈[β-SiW₁₁O₃₉] · 14H₂O 9.3 µmol, water 1 mL, cyclohexanol 1 mmol, hydrogen peroxide 5 mmol, reaction temperature 90 °C, reaction time 7 h.

^a Reaction conditions: K₈[β-SiW₁₁O₃₉] · 14H₂O 9.3 µmol, water 1 mL, substrate 1 mmol, hydrogen peroxide 5 mmol, reaction temperature: 90 °C, isolated yield.

^b 20 µmol of methyltrioctylammonium chloride was added.