Synthesis 2005(15): 2473-2475  
DOI: 10.1055/s-2005-872102
SHORTPAPER
© Georg Thieme Verlag Stuttgart · New York

Synthesis and Characterization of Chiral Imidazolium Salts

Mayra Y. Machado, Romano Dorta*
Departamento de Química, Universidad Simón Bolívar, Caracas, Venezuela
Fax: +58(212)9063961; e-Mail: rdorta@usb.ve;
Further Information

Publication History

Received 27 January 2005
Publication Date:
25 July 2005 (eFirst)

Abstract

Chiral imidazolium salts that can be classified as ionic liquids (ILs) were derived from the ‘chiral pool’ precursors camphor, β-pinene, and tartaric acid. ILs containing chiral imidazolium cations as well as chiral anions were synthesized. Furthermore, the anion of the IL 1-methyl-3-[(S)-2′-methylbutyl]imidazolium tosyl­ate was substituted on an ion-exchange resin for the chiral (S)-camphorsulfonate anion thus forming the first well-characterized ‘doubly chiral’ IL.

    References

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  • 6a

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8

Presumably, methylimidazolium formation is due to Hoffmann type elimination. NMR spectroscopy of crude reaction mixtures indicated concomitant alkene formation.

12

The interchange of anions of similar size, such as OTf-, sulfonates, or BF4 - in the usual CH2Cl2-H2O system is not possible.

13

We found that the classical ILs BMI·BF4 or BMI·PF6 are obtained in a purer form by the ion-exchange method than by the standard CH2Cl2-H2O extraction method.