Chemical synthesis, polymers catalyst preparation

Chemically bonding metal complexes to an insoluble solid is a method of preparing catalysts whose active centers have well-defined structures, but the results have yet to be applied to synthesis. Polymer-... 

H. Grubbs at the California Institute of Technology, he joined the faculty at Cornell University in 1997, where he is now Assistant Professor of Chemistry and Chemical Biology. His research interests include the development of single-site catalysts for synthesis and the preparation and characterization of well-defined polymer architectures. 

Three kinds of PAV films was prepared using methoxy pendant precursors. The chemical structures and synthetic route of the PAV films used in this study are shown in Fig. 19. The details of synthesis of the methoxy pendant precursors have been described in refs. 29 and 30. The precursors were soluble in conventional organic solvents, for example, chloroform, dichloromethane, benzene and so on. The precursor polymer thin films were spin-coated on fused quartz substrates from the chloroform solutions. The precursor films were converted to PAV films by the heat-treatment at 250 0 under a nitrogen flow with a slight amount of HC1 as a catalyst. This method provided high performance PAV films with excellent optical quality. 

Rare earth metal triflates are recognized as a very efficient Lewis acid catalysts of several reactions including the aldol reaction, the Michael reaction, allylation, the Diels-Alder reaction, the Friedel-Crafts reaction, and glycosylation [110]. A polymer-sup-ported scandium catalyst has been developed and used for quinoline library synthesis (Sch. 8) [111], because lanthanide triflates were known to be effective in the synthesis of quinolines from A-arylimines [112,113]. This catalyst (103) was readily prepared from poly(acrylonitrile) 100 by chemical modification. A variety of combinations of aldehydes, amines, and olefins are possible in this reaction. Use of the polymer-supported catalyst has several advantages in quinoline library construction. 

The results obtained show that immobilization of metal complexes in polymer gels allows to prepare physically heterogeneous and chemically homogeneous catalysts and leads to an important increase in their activity, selectivity and stability in the reactions of dimerization of lower olefins. The immobilization of the complexes opens new possibilities of macromolecular design of the catalysts with desired structural organization and will contribute to the development of general principles of synthesis of highly efficient and environmentally friendly catalytic systems for liquid phase processes. 

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