IL-supported

Ionic liquids are characterized by low vapor pressure, permitting operation in a wide temperature range without causing detrimental effect to the catalyst or the ionic liquid. All of Co(II)-IL/Support catalysts were characterized by TGA. Figure 2 illustrates that the novel catalyst system was stable up to almost 360°C. This has allowed us to utilize this catalyst system for applications other than Just hydrocarbon oxidation reactions. 

IL + supporting electrolyte - - alternative negative electrode with higher potential... 

Of particular importance for industry is the hydroformylation of alk-l-enes and one of the best processes developed so far for C2-C5 olefins employs a biphasic system in combination with a hydrosoluble rhodium complex bearing TPPTS as ligand [69-71], From this statement, Wasserscheid et al. investigated in the early 2000s the possibility of using ILs supported catalysts for this reaction [71-75], owing to the discovery by Chauvin that good linear/branched selectivities could be achieved... 

A further aspect to be considered is that supported ILs can also host chemicals, for example, complexing agents, which could further enhance the selectivity in the separation. This concept opens up the possible use of ILs supported on a membrane, particularly ceramictype nano-membranes (e.g., an alumina nanoporous membrane obtained by anodic oxidation) to develop novel systems that can combine catalysis and separation. The concept is shown in Figure 2.14. 

Davis was the first to recognize that functionalized ionic liquids can serve not just as reaction media but as catalysts as well. One advantage of using an IL-supported catalyst is that the catalyst can be recovered simply by solubility difference (Scheme 4.6). 

In addition, efficient recycling of IL-supported catalysts has suggested the possibility of applying the same approach in metal-catalyzed reactions, where the reuse of expensive ligands, metal, or both may be critical. 

In 2003, Guillemine and Yao reported in two independent papers the synthesis of IL-supported catalysts for ring-closing metathesis, whereas a IL-supported palladium complex was found to catalyze the Heck reactions with good recyclability of up to ten cycles. ... 

Recently, some examples of synthetic reagents anchored onto ionic liquids have been reported. These new systems present the advantage of being readily separated from the reaction mixture by simple phase separation after the desired chemical transformation and can then be regenerated and reused. For example, IL-supported hypervalent iodine compounds have been used for the oxidation of alcohols to ketones (Scheme 4.7). 

As in the case of IL-supported peptide synthesis, all the IL-anchored intermediates in Scheme 4.10 were simply purified by washing with ether. 

Kawano and Togo introduced an ionic liquid group into iodoarenes, to form ionic liquid-supported iodoarenes, and used them for the promotion of the synthesis of oxazoles [24]. The results of the reactions of acetonitrile, m-chloroperbenzoic acid (mCPBA), trifluoromethanesulfonic acid (TfOH), and acetophenone are shown in Table 12.1, using various IL-supported iodoarenes (IL-supported Phis). The reactivities of IL-supported iodoarenes (Phis) 17-25 are shown in entries 1-9, and IL-supported Phi 20 showed the best reactivity. Instead of acetonitrile as solvent, room temperature ILs, such as [emim][OTs], [bmim][PFg], and [bmpyjlNTf ], were used in the presence of IL-supported Phi 20 (entries 10-12). However, [emim][OTs] did not promote the oxazole formation at all, while [bmimJPF and [bmpy][NTfJ provided the oxazole in moderate to low yields. Thus, use of acetonitrile as solvent yielded the best reactivity as compared with these ILs. 

Ionic liquid (IL)-supported NHPI was prepared via the synthetic route shown in Scheme 14.58. 

Again, good results were obtained, but nothing was said about the recycling protocol of the IL support. The use of a complex linker does not seem to be a limiting addition, unlike the former system. These acryhc esters have also been used as partners in several other reactions such as 1-4 additions of nucleophiles such as pyrrohdine or thiophenol in the presence of EtjN, Heck coupling and chhydroxylation of the obtained cinnamic esters. Methyl esters could be isolated in... 

To extend the operation period of prolinamide-derived IL-supported catalysts, bis-amides 58a-e were synthesised from (25, 4R)-4-hydro yproline and various diamines. C2-Symmetric compounds 58c-e bearing p-phenyle-nediamine, l,2-diaminocyclohexane or 1,2-diphenyl ethylenedia-mine ° structural units exhibited excellent catalytic performance in asymmetric cross-aldol reactions between ketones 8 and aldehydes 9 in the aqueous medium and could be recycled 15 times without any decrease of activity or loss of enantiocontrol. Furthermore, bis-amide 58e efficiently catalysed aldol reactions of acetone with a-ketoesters 62 to afford a-hydrojqr-y-ketoesters 63 in a nearly quantitative yield, yet with moderate enantioselectivity (Scheme 10.14). 

The vapor pressure of ILs supported on a porous soHd may be lower than the saturation vapor pressure of a pure IL, as known from multilayer ad/desorption of gases. 

Thus, this strongly enhanced enantioselectivity in the reduction of acetophenone over IL supported chiral complei s (Type B) is particularly noteworthy. In parallel to hydrogenation of the keto group, hydrogenation of the phenyl ring (Eq. (10.1)) is observed, which is indicative of enhanced substrate-metal interactions in ILs. 

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