During the emerging years of ionic liquids, they found interest in organic synthesis as reaction media. Synthetic organic chemists used ionic liquids as reaction media to immobilize a suitable metal based or other catalysts incorporating design features to the IL to effect phase separation with products. Ionic liquid reaction media usually prevented leaching of the metal catalyst. This in turn provided the opportunity for continuous and batch reactions associated with catalyst recyclability. The most common organic reactions that have been examined in ionic liquid media are Freidel-Craft’s alkylations and acylations, Heck reaction, Deils-Alder cycloaddtions, Aldol and Knovenagel condensations, trans-esterifications (eg. Biodiesel production).
At QUILL, we have carried out selective hydrogenation of α,β unsaturated aldehydes in a range of room temperature ionic liquids demonstrating enhanced selectivity of supported palladium catalysts for the reduction of the conjugated C C bond (as against reduction of the carbonyl function) compared with conventional molecular organic solvents. Chiral Lewis acid complexes based on copper (II), magnesium (II) and platinum (II) complexes have been used to catalyse asymmetric Mukaiyama aldol (MA) and Diels-Alder (DA) reactions. For the DA reaction a significant enhancement in enantioselectivity was also observed when these reactions were conducted in ionic liquids. The use of a chiral cationic ligand which when metal complexed showed no leaching from the ionic liquid phase during MA reactions. Heterogenisation of these chiral Lewis acids using Supported Ionic Liquid Phase (SILP) onto various metal oxide and carbon supports produced a recyclable catalyst with the same enantioselectivity and yield despite the lower catalytic activity compared to the ionic liquid homogeneous reaction.
We have recently developed a tungsten based chiral catalytic ionic liquid capable of sulfide oxidation to sulfoxides associated with very high ees. H2O2 was the sacrificial oxidant.
At QUILL, we have also developed an idustrial process baised in Ils for production of the fragarance, lilial and fungicide, fenpropimorph.
A series of Hünig’s base tethered ammonium ionic liquids have been used to catalyse the Knoevenagel condensation of aldehydes and ketones. By increasing the distance between the ammonium head group and Hünig’s base the activity of the catalyst was found to increase. The reactions were performed under homogeneous and under biphasic, liquid-liquid SILP conditions.
We have also developed an indium based recylable catalyst system for alkylation and acylation of aromatic compounds, including alkylbenzenes and alcoxybenzenes. The same catalyst sytem is shown to catalyse alkylation of phenols with alkenes and alcohols.
For the first time, at QUILL, we have demonstrated that a course of a chemical reaction can be altered dramatically by changing the ionic liquid medium where the reaction was performed. For example, the reaction of toluene and nitric acid in three different ionic liquids gives rise to three completely different products, nitrotoluene, halotoluene or benzoic acid, in high yields.
References
1. Rodil, E., Aldous, L., Hardacre, C. and Lagunas, M.C., "Preparation of AgX (X = Cl, I) nanoparticles using ionic liquids", Nanotechnology, 19, 105603/105601-105603/105608 (2008).
2. Hardacre, C., Nancarrow, P., Rooney, D.W. and Thompson, J.M., "Friedel-Crafts Benzoylation of Anisole in Ionic Liquids: Catalysis, Separation, and Recycle Studies", Org. Process Res. Dev., 12, 1156-1163 (2008).
3. Earle, M., "Stoichiometric organic reactions and acid-catalyzed reactions in ionic liquids", in Ionic Liquids in Synthesis, 2nd Edit., Eds. T. Welton and P. Wasserscheid, Vol. 1 (Wiley-VCH, Weinheim, 2008), pp. 292-367.
4. Amigues, E.J., Hardacre, C., Keane, G. and Migaud, M.E., "Solvent-modulated reactivity of PCl3 with amines", Green Chem., 10, 660-669 (2008).
5. Lombardo, M., Pasi, F., Trombini, C., Seddon, K.R. and Pitner, W.R., "Task-specific ionic liquids as reaction media for the cobalt-catalysed cyclotrimerisation reaction of arylethynes", Green Chem., 9, 321-322 (2007).
6. Forsyth, S.A., Gunaratne, H.Q.N., Hardacre, C., McKeown, A. and Rooney, D.W., "One-Pot Multistep Synthetic Strategies for the Production of Fenpropimorph Using an Ionic Liquid Solvent", Org. Process Res. Dev., 10, 94-102 (2006).
7. Deetlefs, M., Seddon, K.R. and Shara, M., "Neoteric optical media for refractive index determination of gems and minerals", New J. Chem., 30, 317-326 (2006).
8. Amigues, E., Hardacre, C., Keane, G., Migaud, M. and O'Neill, M., "Ionic liquids-media for unique phosphorus chemistry", Chem. Commun., 72-74 (2006).
9. Villagran, C., Banks, C.E., Pitner, W.R., Hardacre, C. and Compton, R.G., "Electroreduction of N-methylphthalimide in room temperature ionic liquids under insonated and silent conditions", Ultrason. Sonochem., 12, 423-428 (2005).
10. Forsyth, S.A., Gunaratne, H.Q.N., Hardacre, C., McKeown, A., Rooney, D.W. and Seddon, K.R., "Utilisation of ionic liquid solvents for the synthesis of Lily-of-the-Valley fragrance {β-Lilial®; 3-(4-t-butylphenyl)-2-methylpropanal}", J. Mol. Catal. A: Chem., 231, 61-66 (2005).
11. Earle, M.J., Hakala, U., Hardacre, C., Karkkainen, J., McAuley, B.J., Rooney, D.W., Seddon, K.R., Thompson, J.M. and Waehaelae, K., "Chloroindate(III) ionic liquids: recyclable media for Friedel-Crafts acylation reactions", Chem. Commun., 903-905 (2005).
12. Davey, P.N., Forsyth, S.A., Gunaratne, H.Q.N., Hardacre, C., McKeown, A., McMath, S.E.J., Rooney, D.W. and Seddon, K.R., "Synthesis of 3-(4-tert-butylphenyl)-2-methyl-2-propenal, a precursor to Lilial, via an aldol condensation in an ionic liquid", Green Chem., 7, 224-229 (2005).
13. Hardacre, C., Katdare, S.P., Milroy, D., Nancarrow, P., Rooney, D.W. and Thompson, J.M., "A catalytic and mechanistic study of the Friedel-Crafts benzoylation of anisole using zeolites in ionic liquids", J. Catal., 227, 44-52 (2004).
14. Earle, M.J., Katdare, S.P. and Seddon, K.R., "Paradigm Confirmed: The First Use of Ionic Liquids to Dramatically Influence the Outcome of Chemical Reactions", Org. Lett., 6, 707-710 (2004).
15. Doherty, S., Goodrich, P., Hardacre, C., Luo, H.-K., Rooney, D.W., Seddon, K.R. and Styring, P., "Marked enantioselectivity enhancements for Diels-Alder reactions in ionic liquids catalysed by platinum diphosphine complexes", Green Chem., 6, 63-67 (2004).
16. Seddon, K.R. and Stark, A., "Selective catalytic oxidation of benzyl alcohol and alkylbenzenes in ionic liquids", Green Chem., 4, 119-123 (2002).
17. Earle, M.J. and Seddon, K.R., "Clean synthesis in ionic liquids", in Molten Salts XIII, Vol. 2002-19 (American Chemical Society, 2002), pp. 177-189.
18. Earle, M.J., "Ionic liquids: Solvents for the twenty-first century", in Ionic Liquids: Industrial Applications for Green Chemistry, Eds. R.D. Rogers and K.R. Seddon, ACS Symposium Series, Vol. 818 (American Chemical Society, Washington, 2002), pp. 90-105.
19. Lau, R.M., van Rantwijk, F., Seddon, K.R. and Sheldon, R.A., "Lipase-Catalyzed Reactions in Ionic Liquids", Org. Lett., 2, 4189-4191 (2000).
20. Earle, M.J., Seddon, K.R. and McCormac, P.B., "The first high yield green route to a pharmaceutical in a room temperature ionic liquid", Green Chem., 2, 261-262 (2000).
Powered by Joomla. For website enquiries contact Webmaster at webquill@qub.ac.uk.
