abstracts - Институт катализа им. Г.К. Борескова

CATALYSIS IN IONIC LIQUIDSPL-5Hardacre C.School of Chemistry and Chemical Engineering, Queen’s University, Belfast, UKE-mail: c.hardacre@qub.ac.ukIonic liquids are versatile solvents for both heterogeneously and homogeneously catalysedreactions. A wide range of reactions have been demonstrated from liquid phase reactionssuch as Diels-Alder and aldol transformations as well as liquid-gas reactions such ashydrogenations and oxidations. This paper illustrates this range of reactions with a focus onthe difference between ionic liquids and molecular solvents; the mechanisms of the processesand the recyclability of the ionic liquid and catalyst system.Ionic liquids have been studied extensively as clean solvents for a wide range of chemistry.This interest is a direct result of the diverse physical properties which these liquids have andthe way in which they may be systematically varied, for example the density, viscosity andwater miscibility. Since they also have effectively zero vapour pressure this makes them idealengineering solvents for reactive chemistry, allowing direct distillation from the solvent andsimple solvent recycle without the production of VOC’s. 1 A wide range of reactions havebeen performed in ionic liquids to date including alkylations, 2 C-C bond coupling reactions, 3-5polymerisations, 6-8 hydrogenations, 9, 10 hydroformylation, 11 and alkoxycarbonylation. 12 Thesereactions have been extensively reviewed. 13 Many of the reactions reported in ionic liquidsare catalytic, using homogeneous, enzyme and heterogeneous catalysts with the vast majorityusing homogeneous. This paper describes a range of catalytic processes using homogeneousand heterogeneous catalysts as well as utilising the ionic liquid as a catalyst.Despite the large number of reactions performed in ionic liquids, few have demonstrated thatthe ionic medium has a positive effect on the enantioselectivity for asymmetrictransformations. The majority of studies concerning catalytic enantioselective reactions haveused the ionic liquid in combination with a molecular co-solvent. In many cases no beneficialeffect on the enantioselectivity compared with the conventional media is found although therecyclability of the catalyst is improved. In contrast, we have demonstrated that ionic liquidscan not only significantly increase the rate of platinum catalysed asymmetric Diels-Alderreactions and the recyclability of the catalyst but also allow high enantioselectivities to beachieved without the need to recourse to low temperatures. 14 Using conformationally flexibleinexpensive ligands the ionic liquid slows the rate of racemisation of the catalyst comparedwith dichloromethane, increasing the enantioselectivity achieved. This system also allows for15