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Synlett 2010(18): 2818-2822  
DOI: 10.1055/s-0030-1259005
LETTER
© Georg Thieme Verlag Stuttgart ˙ New York

Mild and Selective Oxidation of Alcohols Using Oxone® as An Oxidant Catalyzed by Palygorskite in Water

Shang Wu, Hengchang Ma, Ziqiang Lei*
Key Laboratory of Polymer Materials of Gansu Province, Key Laboratory of Eco-Environment-Related Polymer Materials, Ministry of Education, College of Chemistry and Chemical Engineering, Northwest Normal University, Lanzhou 730070, P. R. of China
Fax: +86(931)7971687; e-Mail: leizq@nwnu.edu.cn;
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Publication History

Received 30 June 2010
Publication Date:
14 October 2010 (online)

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Abstract

Palygorskite, a natural, environmentally friendly and inexpensive fibrillar silicate clay mineral, was applied as a catalyst in the oxidation of alcohols in aqueous media. The oxidation transformation effectively proceeded in the presence of an environmentally benign oxidant Oxone®. Benzyl alcohols, benzhydrols, cyclic and aliphatic alcohols could be oxidized to their corresponding acids or ketones in moderate to high yield and good selectivity at 50 ˚C or 70 ˚C in 21 hours.

Key words

alcohols - oxidation - ketenes - carboxylic acid - silicon

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Preparation of ¹8 O-Enriched Benzyl Alcohol: Na (0.05 g) was added to ¹8O-enriched water (0.75 mL, 98% H2 ¹8O, Huayi Isotope Co.) in a flask, and then 1-chloromethyl-benzene (0.5 mL) was added into the flask. The mixture was heated to 95 ˚C and refluxed for 48 h with continuous stirring. The product was purified by column chromatog-raphy and C6H5CH2 ¹8OH (0.2 g) was obtained. The ¹8O-enriched benzyl alcohol was examined by GC-MS, and the abundance of C6H5CH2 ¹8OH was determined to be 98%.

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General Procedure for Oxidation of Alcohols: The required amount of Oxone® and palygorskite was added to a solution of the alcohol (2 mmol) in H2O (10 mL). Then, the mixture was stirred at 50 ˚C for 21 h and monitored by TLC. After completion of the reaction, the aqueous phase was extracted with EtOAc (3 × 4 mL). The organic layer was dried over anhyd Na2CO3, and the solvent was removed under reduced pressure to give the desired crude product. Analytically pure products were obtained after recrystal-lization or column chromatography using petroleum ether and EtOAc as eluent. Formation of products and consumption of substrates were monitored by GC. The identity of products was determined either by comparison with authentic samples using gas chromatography or by GC-MS or NMR analysis.