Polymethacrylate-based catalysts

Gelbard, G., Breton, R, Quenard, M., et al. (2000). Epoxidation of Cyclohexene with Polymethacrylate-Based Peroxotungstic Catalysts, J. Mol. Catal. A Chem., 153, pp. 7-18 Gelbard, G., Gauducheau, T., Vidal, E., et al. (2002). Epoxidation with Peroxotungstic Acid Immobilised onto Silica-Grafted Phosphoramides, J. Mol. Catal. A Chem., 182-183, pp. 257-266. 

Synthetic organic polymers, which are used as polymeric supports for chromatography, as catalysts, as solid-phase supports for peptide and oligonucleotide synthesis, and for diagnosis, are based mainly on polystyrene, polystyrene-divinylbenzene, polyacrylamide, polymethacrylates, and polyvinyl alcohols. A conventional suspension of polymerization is usually used to produce these organic polymeric supports, especially in large-scale industrial production. 

The values of Katrp for numerous alkyl halide - copper catalyst combinations have been determined (21,27) using modified kinetic equations describing the accumulation of the deactivator XCu Ln due to the persistent radical effect.(28) Figure 3 shows that the values of Katrp for the same alkyl halide (ethyl 2-bromoisobutyrate, EtBriB, which mimics the dormant chains of a polymethacrylate) vary by more than seven orders of magnitude as the N-based ligand is changed. Since the solvent and the alkyl halide used in all measurements were the same, the values of Kbh and Kea (eq. 1) were constant and the variations in Katrp were cansed by differences in the electron transfer equilibrium constant and the halidophihcity of the Cu complexes. 

Because the thermal stability of polystyrenes and polymethacrylates is limited to 200°C, continuous use of a polymer-supported reactive species tends to be limited to significantly lower temperatures than this (see polymeric sulphonic acids). There is considerable interest in supporting, in particular, alkene oxidation catalysts on polymers and to operate reactions at temperatures above 200°C. To achieve this, novel thermo-oxidatively stable supports are required and some progress has been made in this direction. More details of specific applications will be given later, but supports based on, for example, polyacrylonitrile [50-52], polyamides [53-56], polysulphone [57, 58], polyaniline [59] and polybenzimidazole... 

Chiral polymers can be obtained in two different ways. The use of a chiral catalyst during polymerization can lead to helical structures, as observed in polysaccharides. The other synthesis path uses chiral monomers, which are polymerized to give a chiral polymer capable of folding to a supramolecular stmcture [20]. For application in HPLC, all of these polymers must be coated onto silica, since they are imable to withstand the high pressures encountered in HPLC. Currently, chiral stationary phases based on polyacrylates or polymethacrylates play only a minor role. Chirasphere (Merck) is derived from a silica material coated with poly(N-acryloyl-(S)-phenylalanine ethyl ester) and can be used for the separation of P-blockers in the normal-phase mode. The chiral polymethacrylates Chiralpak OP and Chiralpak OT (Daicel) are able to separate aromatic compounds into their enantiomers. 

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