Polymer-supported ionic liquid

Another example in which perruthenate immobilized on a polymer-supported ionic liquid is used for the promotion of the aerobic oxidation of alcohols is reported by Xie and his group [43]. The catalyst preparation represented in Scheme 14.41. 

Scheme 14.41 Preparation of a perruthenate immobilized on a polymer-supported ionic liquid...

Xie Y, Zhang Z, Hu S, Song J, Li W, Han B (2008) Aerobic oxidation of benzyl alcohol in supercritical CO catalyzed by perruthenate immobilized on polymer supported ionic liquid. Green Chem 10 278-282... 

Substitution. CsF is an excellent fluoride ion source for converting alkyl mesylates to RF, especially in the presence of the imidazolium mesylate 1. The effect, due to hydrogen bonding to the tertiary alcohol to render the fluoride ion more nucleophilic but less basic (so as to minimize elinination [H-OMs]), is also manifested in a polymer-linked 1, and a combination of r-AmOH and a polymer-supported ionic liquid. ... 

Even though most of the supported ionic liquid catalysts prepared thus far have been based on silica or other oxide supports, a few catalysts have been reported where other support materials have been employed. One example involves a polymer-supported ionic liquid catalyst system prepared by covalent anchoring of an imidazolium compound via a linker chain to a polystyrene support [79]. Using a multi-step synthetic strategy the polymeric support (e.g. Merrifield resin among others) was modified with l-hexyl-3-methylimidazolium cations (Scheme 5.6-4) and investigated for nucleophilic substitution reactions including fluorina-tions with alkali-metal fluorides of haloalkanes and sulfonylalkanes (e.g. mesylates, tosylates and triflates). 

Polymer-supported Ionic liquid electrolyte layer... 

Z.T. Wang, S.C. Wang, L.W. Xu, Polymer-supported ionic-liquid-catalyzed synthesis of 1,2,3,4-tetrahydro- 2-oxopyrimidine-5-carboxylates... 

Ionic liquids have already been demonstrated to be effective membrane materials for gas separation when supported within a porous polymer support. However, supported ionic liquid membranes offer another versatile approach by which to perform two-phase catalysis. This technology combines some of the advantages of the ionic liquid as a catalyst solvent with the ruggedness of the ionic liquid-polymer gels. Transition metal complexes based on palladium or rhodium have been incorporated into gas-permeable polymer gels composed of [BMIM][PFg] and poly(vinyli-dene fluoride)-hexafluoropropylene copolymer and have been used to investigate the hydrogenation of propene [21]. 

Work with supported ionic liquids was extended to a cationic polymer, poly (diallyldimethylammonium chloride), which has quaternary ammonium functional groups (Fig. 16) 268). The extra-structural counter anion is Cl . The polymer was applied to simultaneously incorporate an ionic liquid and a transition-metal catalyst via a simple mixing of the components. Wilkinson s catalyst and [BMIM]PF6 were... 

SILP systems have proven to be interesting not only for catalysis but also in separation technologies [128]. In particular, the use of supported ionic liquids can facilitate selective transport of substrates across membranes. Supported liquid membranes (SLMs) have the advantage of liquid phase diffusivities, which are higher than those observed in polymers and grant proportionally higher permeabilities. The use of a supported ionic liquid, due to their stability and negligible vapor pressure, allow us to overcome the lack of stability caused by volatilization of the transport liquid. SLMs have been applied, for example, in the selective separation of aromatic hydrocarbons [129] and CO2 separation [130, 131]. 

The concept of immobilized ionic liquids entrapped, for instance, on the surface and pores of various porous solid materials (supported ionic liquid phase, SILP) is rapidly become an attractive alternative. In addition, the SILPs can also answer other important issues, such as the difficult procedures for product purification or IL recycling, some toxicity concerns and the problems for application in fixed-bed reactors, which should be addressed for future industrial scale-up. This new class of advanced materials shares the properties of true ILs and the advantages of a solid support, in some cases with an enhanced performance for the solid material. Nevertheless, a central question for the further development of this class of materials is to understand how much the microenvironment provided by the functional surfaces is similar or not to that imparted by ILs. Recent studies carried out using the fluorescence of pyrene to evaluate the polarities of a series of SILPs based on polymeric polystyrene networks reveal an increase in polarity of polymers, whereas the polymer functional surfaces essentially maintain the same polarity as the bulk ILs. However, this is surely not a simple task, in particular if we consider that the basic knowledge of pure ILs is still in its infancy, and we are just starting to understand the fundamentals of pure ILs when used as solvents. 

Catalytically active supported ionic liquid membranes were used for propylene/propane vapor mixture separation. In this case, the ionic Hquid was immobilized in the pores of an asymmetric ceramic support, displaying sufficient permeability, good selectivity, and long-term stabUity [51]. Porous inorganic membranes were also used as a support for chiral-selective liquid membranes. For this purpose, porous tubular ceramic membranes were impregnated with 3-cyclodextrin polymer. Such SLMs were used for separation of enantiomers of racemic pharmaceutical chlorthahdone [52]. 

Extensive efforts have been made in recent years to prepare polymer or ionic-liquid-supported 4-hydro3qq3rolinamide derivatives that would combine the high catalytic activity and efficient stereocontrol of unsupported prolinamides with the significant water tolerance and recyclability of immobilised organocatalysts in useful catalytic transformations (Figure 10.5). 

Figure 10.5 Polymer or ionic-liquid-supported 4-hydroxyprolinamide derivatives.

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Virtanen P., Karhu H., Kordas K Mikkola J.P. (2007). The effect of ionic liquid in supported ionic liquid catalysts (sdca) in the hydrogenation of a, 3-unsaturated aldehydes. Chem. Eng. Set, vol.62, n°14, pp.3660-3671, (July 2007), ISSN 0009-2509 Washiro S., Yoshizawa M., Nakajima H. and Ohno H. (2004). Highly ion conductive flexible films composed of network polymers based on polymerizable ionic liquids. Polymer vol.45, n°5, pp. 1577-1582 (March 2004), ISSN 0032-3861 Wasserscheid P. Keim W.A. (2000). Ionic Liquids—New "Solutions" for Transition Metal Catalysis, Ang. Chem. Int. Ed., vol.39, pp.3772-3789, (November 2000), Online ISSN 1521-3773... 

As with organic solvents, proteins are not soluble in most of the ionic liquids when they are used as pure solvent. As a result, the enzyme is either applied in immobilized form, coupled to a support, or as a suspension in its native form. For production processes, the majority of enzymes are used as immobilized catalysts in order to facilitate handling and to improve their operational stability [24—26]. As support, either inorganic materials such as porous glass or different organic polymers are used [27]. These heterogeneous catalyst particles are subject to internal and external... 

Abstract Current microwave-assisted protocols for reaction on solid-phase and soluble supports are critically reviewed. The compatibility of commercially available polymer supports with the relatively harsh conditions of microwave heating and the possibilities for reaction monitoring are discussed. Instrmnentation available for microwave-assisted solid-phase chemistry is presented. This review also summarizes the recent applications of controlled microwave heating to sohd-phase and SPOT-chemistry, as well as to synthesis on soluble polymers, fluorous phases and functional ionic liquid supports. The presented examples indicate that the combination of microwave dielectric heating with solid- or soluble-polymer supported chemistry techniques provides significant enhancements both at the level of reaction rate and ease of purification compared to conventional procedures. 

The microwave-assisted thionation of amides has been studied by Ley and coworkers using a polymer-supported thionating reagent [115]. This polymer-supported amino thiophosphate serves as a convenient substitute for its homogeneous analogue in the microwave-induced rapid conversion of amides to thioamides. Under microwave conditions, the reaction is complete within 15 min, as opposed to 30 h by conventional reflux in toluene (Scheme 7.95). The reaction has been studied for a range of secondary and tertiary amides and GC-MS monitoring showed that it proceeded almost quantitatively. More importantly, this work was the first incidence of the use of the ionic liquid l-ethyl-3-methylimidazolium hexafluorophosphate... 

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