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Issue 8, 2009
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Fischer indole synthesis catalyzed by novel SO3H-functionalized ionic liquids in water

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Abstract

Novel SO3H-functionalized ionic liquids bearing two alkyl sulfonic acid groups in the imidazolium cations were designed and successfully applied as catalysts for the one-pot Fischer indole synthesis in water medium. The sequence of the catalytic activity observed in the transformation was in good agreement with the Brønsted acidity order determined by the Hammett method. Various types of indoles from single-carbonyl ketones/aldehydes and cyclohexandiones were provided in 68–96% yields using the catalytic system of [(HSO3-p)2im][HSO4]/H2O. The indole products could be conveniently separated from the reaction mixture by filtration and the dissolved catalyst could be regenerated by treatment with a strongly acidic cation exchange resin, which meant the whole process was performed in water without using any organic solvents.

Graphical abstract: Fischer indole synthesis catalyzed by novel SO3H-functionalized ionic liquids in water

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Supplementary files

Article information


Submitted
16 Jan 2009
Accepted
12 May 2009
First published
04 Jun 2009

Green Chem., 2009,11, 1239-1246
Article type
Paper

Fischer indole synthesis catalyzed by novel SO3H-functionalized ionic liquids in water

D. Xu, J. Wu, S. Luo, J. Zhang, J. Wu, X. Du and Z. Xu, Green Chem., 2009, 11, 1239
DOI: 10.1039/B901010F

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