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SYNTHESIS
As an example, the rate and selectivities of the Diels-Alder reaction between cyclopentadiene and methyl acrylate was studied in a number of neutral ionic liquids by Welton [2]. Other well investigated reactions are nucleophilic substitutions. A quantitative study on the cyanide displacement of benzyl chloride to yield phenylacetonitrile was performed by Eckert [3]. Even a complete synthesis of a pharmaceutical, Pravadoline has been performed in the ionic liquid [BMIM][PF6] [4]. A fairly novel use of this ionic liquid is to enhance microwave absorption and hence accelerate the rate of a reaction as demonstrated in the thionation of amides [5]. A lot of Organometallic reactions such as addition to carbonyl compounds or alkylborane reduction of aldehydes to alcohols have also been performed in ionic liquids [6-7]. Of great commercial interest is the improvement of the harsh reaction conditions employed in the halex-reaction (chlor-fluorine exchange). Wasserscheid has shown [8] that it is possible to significantly lower the reaction temperatures and thus omit the use of sulfolane when performing this reaction in a diglyme/ionic liquid mixture.
Solvent Innovation offers a synthesis and catalysis kit with specially selected ionic liquids. For detailed information about more reactions that have been performed in ionic liquids please contact markus.wagner@solvent-innovation.com [1] J. S. Wilkes et al., J. Org. Chem. 1986 , 51 , 480-483. [2] T. Welton et al., Tetrahedron Lett. 1999 , 40 , 793-795. [3] C. A. Eckert, Chem Commun. 2001 , 887-888. [4] K. R. Seddon et al., Green Chem. 2000 , 2 , 261-262. [5] S. V. Ley et al., J. Chem. Soc., Perkin Trans. 1 2001 , 358-361. [6] C. M. Gordon, A. McClusky, Chem Commun. 1999 , 143-144. [7] G. W. Kabalka, R. R. Malladi , Chem. Commun. , 2000 , 2191. [8] P. Wasserscheid et al., Chem. Commun. , 2004 , in press .
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NEWS
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One of the most important and rapidly increasing applications of ionic liquids is their use as solvent in organic synthesis. The Friedel-Crafts acylation in chloroaluminate(III) salts was among the first investigated reactions [1]. However, these salts are watersensitive and must be handled under dry conditions. Since the introduction of water-stable "neutral" ionic liquids in the early 90s the range and scope of organic reactions has grown to include most of the classical organic reactions.