Ionic Liquids as Solvents

Ionic Liquids as Solvents for Organic Synthesis and Catalysis

Ionic liquids (ILs) have established themselves as designer solvents[i] for synthesis and catalysis, since they allow for fine-tuning of their properties by varying cations, anions and substituents. This means that in principle for every reaction a suitable ionic liquid can be identified which may improve the following issues:

  • reaction yield
  • reaction rate
  • selectivity
  • milder conditions
  • separation of the product
  • separation and reuse of the catalyst

A well-chosen IL allows an easy separation from the formed product and a recovery of often expensive catalysts. Furthermore, by addition of a co-solvent the miscibility between product(s), catalysts and starting materials can often be fine-tuned. [ii]

Many ILs are known to be stable towards reduction, oxidation, moisture and air, allowing their use as solvents in both oxidations and reductions. Another interesting field is the often sufficient to good solubility of compounds, having only a poor solubility in molecular solvents or which may only dissolved under drastic and/or hazardous conditions. One of the most striking examples is the use of ionic liquids for the dissolution of biomass, in particular of cellulose. [iii]

ILs have been shown to be compatible with

  • transition metal catalysis[iv]
  • organo-catalysis[v]
  • enzyme catalysis.[vi]

A brought variety of ILs with weakly coordinating counter-ions, compatible with sensitive catalysts, is now available. It has been demonstrated that ILs also can be applied to preparation and reuse of nanoparticle catalysts.[vii] However, small amounts of impurities, which are often originated from the production of ILs, can have tremendous (and often negative) impact on the yield and selectivity of the catalytic reaction. IOLITEC offers a wide spectrum of high purity ionic liquids, suitable for catalytic reactions. In addition, screening kits are available for purchase.

If you are interested in using ILs for synthesis and catalysis, please do not hesitate to contact us.

Text: Dr. Svetlana Tšupova, 2017.

[II C.2] [II C.3]

 

 


[i] Freemantle, M. Chem. Eng. News 1998, 76, 32.

[ii] Doherty, S.; Goodrich, P.; Hardacre, C.; Luo, H. K.; Rooney, D. W.; Seddon, K. R.; Styring, P. Green Chem. 2004, 6, 63.

[iii] Swatloski, R. P.; Spear, S. K.; Holbrey, J. D.; Rogers, R. D. J. Am. Chem. Soc. 2002, 124, 4974

[iv] Wasserscheid, P. Transition Metal Catalysis in Ionic Liquids, Wiley 2010

[v] Qiao, Y.; Headley, A. D. Catalysts 2013, 3, 709; Chowdari, N. S.; Ramachary, D. B., Barbas III, C. F. Synlett 2003, 1906.

[vi] Irimescu, R. J. Mol. Catal. B: Enzym. 2004, 30, 189.

[vii] Curran, D. P.; Fischer, K.; Moura-Letts, G. Synlett 2004, 1379, Selvakumar, K.; Zapf, A.; Beller, M. Org. Lett. 2002, 4, 3031.