Catalyst, Polymer-supported

Keywords acrylates, acrylamides, fumarates, a, -unsaturated ketones, vinyl ethers, vinyl sulphoxides, chiral dienophiles, chiral dienes, chiral catalysts polymer-supported chiral Lewis acids... 

The nucleophilic displacement of halogens in aromatic compounds by fluorine is aided by utilizing an appropriate catalyst. Polymer-supported aminopyridinium salts have been found to be versatile catalysts for the synthesis of aryl fluorides. The advantage of the catalyst is that it can be recycled and used again. l-Chloro-4-nitrobenzene (3) is converted to l-fluoro-4-nitrobenzene (4) in 71 % isolated yield using this method. The catalyst used has the structure 5.91... 

When considering the easy recovery and reuse of chiral catalysts, or simple separation process of the product from chiral catalyst, polymer-supported catalysts are very attractive [1,3]. For the enantioselective ethylation using dialkylz-inc, Frechet and Itsuno s group and our group developed polystyrene-supported amino alcohols [1]. 

In order to increase the throughput of the system, the authors subsequently investigated the use of an alternative catalyst, polymer-supported scandium triflate (PS-Sc(OTf)2) 135. As Table 18 illustrates, compared to PS-RuC13 133, the PS-Sc(OTf)2 135 was found to be a more active catalyst toward the Strecker reaction and afforded the target a-aminonitriles in... 

ORGANIC BASE-SUPPORTED CATALYSTS Polymer-supported Catalysts... 

Tetrapropylammonium perruthenate Pr4N+Ru04 and N-methylmorpholine-N-oxide (NMO) as catalytic oxidants of primary, secondary, allylic and benzylic alcohols to carbonyl derivatives. The same catalyst polymer supported perruthenate (PSP) used as efficient oxidant (see 1st edition). 

Trying to overcome the issue of catalyst separation and Pd recovery, researcher have used immobilized Pd catalysts (polymer supported Pd catalysts... 

Polyquiaolines have been used as polymer supports for transition-metal cataly2ed reactions. The coordinatkig abiUty of polyqukioline ligands for specific transition metals has allowed thek use as catalysts ki hydroformylation reactions (99) and for the electrochemical oxidation of primary alcohols (100). 

The polymer-supported catalysts are thus important conceptually in linking catalysis in solutions and catalysis on supports. The acid—base chemistry is fundamentally the same whether the catalytic groups are present in a solution or anchored to the support. The polymer-supported catalysts have replaced acid solutions in numerous processes because they minimise the corrosion, separation, and disposal problems posed by mineral acids. 

Polymer-supported catalysts incorporating organometaUic complexes also behave in much the same way as their soluble analogues (28). Extensive research has been done in attempts to develop supported rhodium complex catalysts for olefin hydroformylation and methanol carbonylation, but the effort has not been commercially successful. The difficulty is that the polymer-supported catalysts are not sufftciendy stable the valuable metal is continuously leached into the product stream (28). Consequendy, the soHd catalysts fail to eliminate the problems of corrosion and catalyst recovery and recycle that are characteristic of solution catalysis. 

This is an ion-exchanger like the sulfonated polymer. The siUca surface can also be functionalized with phosphine complexes when combined with rhodium, these give anchored complexes that behave like their soluble and polymer-supported analogues as catalysts for olefin hydrogenation and other reactions ... 

Transition-metal organometallic catalysts in solution are more effective for hydrogenation than are metals such as platinum. They are used for reactions of carbon monoxide with olefins (hydroformyla-tion) and for some ohgomerizations. They are sometimes immobihzed on polymer supports with phosphine groups. 

S. Bhattacharyya, Polymer-supported reagents and catalysts Recent advances in synthetic applications. Comb Chem High Throughput Screening 3 65-92 2000. 

Polymer supported reagents, catalysts, protecting groups, and mediators can be used in place of the corresponding small molecule materials (Sherrington, 1991 Sundell and Nasman, 1993). The reactive species is tightly bound to a macromolecular support which immobilizes it. This generally makes toxic, noxious, or corrosive materials much safer. The use of polystyrene sulfonic acid catalyst for the manufacture of methyl r-butyl... 

Polymer-supported tetraphenylphosphonium bromide is a recyclable catalyst for halogen-exchange reactions. The reaction of 1 equivalent of chloro-2,4-dinitrobenzene with 1 5 equivalents of spray-dned potassium fluoride and 0.1 equivalent of this catalyst in acetonitnle at 80 C for 12 h gives 2,4-dinitro-fluorobenzene m 98% yield An 11% yield is obtained without the catalyst [3 /]. 

New templated polymer support materials have been developed for use as re versed-phase packing materials. Pore size and particle size have not usually been precisely controlled by conventional suspension polymerization. A templated polymerization is used to obtain controllable pore size and particle-size distribution. In this technique, hydrophilic monomers and divinylbenzene are formulated and filled into pores in templated silica material, at room temperature. After polymerization, the templated silica material is removed by base hydrolysis. The surface of the polymer may be modified in various ways to obtain the desired functionality. The particles are useful in chromatography, adsorption, and ion exchange and as polymeric supports of catalysts (39,40). 

The polymer-supported chiral oxazaborolidinone catalyst 5 prepared from valine was found by Ituno and coworkers to be a practical catalyst of the asymmetric Diels-Alder reaction [7] (Scheme 1.12). Of the several cross-linked polymers with a... 

A more effecdve catalyst for the Hetuy reacdon is a polymer-supported base such as amberlyst A-31. Various fi-nitro alcohols can be obtained v/ith the help of amberlyst v/ith or without solvent fEq, 3,14, A recent report claims that amberlite IRA-430 COH-formi or DOWEX-1 COH-formi is more effecdve for the Henry reacdon than amberlyst A-31/ Poly-... 

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]. 

Murakami, Y. Functionaiited Cyclophanes as Catalysts and Enzyme Models. 115, 103-151 (1983). Mutter, M., and Pillai, V. N. R. New Perspectives in Polymer-Supported Peptide Synthesis. 106, 119-175 (1982). 

Ford, W. T. and Tomoi, M. Polymer-Supported Phase Transfer Catalyst Reaction Mechanisms. Vol. 55, pp. 49—104. 

Large yields of polymer seem to be obtained only when polymerization proceeds on the outer catalyst surface, because the transport of high molecular polyethylene from catalyst pores is impossible (112). The working part of the specific surface of the catalyst can be expected to increase with diminishing strength of links between catalyst particles (112). Therefore, to obtain a highly active catalyst a support with large pore volume should be used (e.g. silica with pore volume >1.5 cm8/g). 

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