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Synlett 2008(10): 1539-1542  
DOI: 10.1055/s-2008-1078416
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© Georg Thieme Verlag Stuttgart · New York

Dehydrative Amination of Alcohols in Water Using a Water-Soluble Calix[4]resorcinarene Sulfonic Acid

Seiji Shirakawa, Shoichi Shimizu*
Department of Applied Molecular Chemistry and High Technology Research Center, College of Industrial Technology, Nihon University, Narashino, Chiba 275-8575, Japan
Fax: +81(47)4742579; e-Mail: s5simizu@cit.nihon-u.ac.jp;
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Publication History

Received 5 January 2008
Publication Date:
16 May 2008 (online)

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Abstract

A protocol for the dehydrative amination of alcohols in water using a water-soluble calix[4]resorcinarene sulfonic acid as a reusable multifunctional catalyst was developed.

Key words

aminations - calixarenes - green chemistry - host-guest systems - phase-transfer catalysis

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The reactions using simple aliphatic alcohols such as hexanol and cyclohexanol gave no amination product.

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General Experimental Procedure for Dehydrative Amination in H 2 O (Table 2): Alcohol (0.30 mmol) and p-toluenesulfonamide (0.45 mmol) were added to a solution of water-soluble calix[4]resorcinarene sulfonic acid 1 13,20 (0.030 mmol) in H2O (1 mL) with stirring, and the reaction mixture was vigorously stirred at 60 °C for an additional 24 h. After the addition of sat. aq NaHCO3 solution (3 mL), the resulting mixture was extracted with EtOAc (3 × 3 mL). The combined extracts were dried over anhyd Na2SO4 and evaporated. The products were purified by flash chromatography on silica gel to yield the amination product.
Recycling Experiments (Table 3): Alcohol (0.90 mmol) and p-toluenesulfonamide (1.08 mmol) were added to a solution of water-soluble calix[4]resorcinarene sulfonic acid 1 (0.090 mmol) in H2O (3 mL) with stirring, and the reaction mixture was vigorously stirred at 60 °C for an additional 24 h. After each reaction, EtOAc (3 mL) was added to the reaction mixture, and the solution was stirred for 5 min. The resulting mixture was allowed to stand for 5 min and then the organic phase was removed via a syringe. This extraction procedure was repeated twice. The remaining aqueous catalyst solution was reused directly in the next cycle. Isolation of the amination product 2a was performed in a manner similar to that described above.