Organocatalysts polymer-supported

Polymer-supported organocatalysts have been used for cycloaddition of ketene, 127, to chloral, 128 [141]. Use of homo-acrylate polymers of cinchona alkaloids led to formation of the desired /Mactone (S)-130 with enantioselectivity up to... 

Polymer-Supported Organocatalysts Based on Amino Acids 285... 

In summary, development of functional polymers that can act as efficient organocatalysts is at the origin of the application of modified polymers as reagents and catalysts in chemistry. To date, the most successful accomplishments have been carried out in the area of basic and acid catalysts. Not surprisingly, this area includes some of the most important industrial applications for supported reagents and catalysts. In general, the development of non-chiral polymer-supported organocatalysts is a field of research that involves both industrial and academic research. In many cases, it has been possible to demonstrate how the use of the... 

Polymer-supported organocatalysts are valuable materials for conducting catalytic asymmetric transformations under simple and environmentally begnin conditions [275]. A novel polymer-supported diphenylprolinol trimethylsilyl ether was synthesized by Hansen et oi. [276], and further applied as catalyst to induce a diastereo- and enantioselective three-component domino Michael/Michael/aldol... 

With the increasing interest in developing catalysts able to be easily separated from the final product, many efforts have been devoted to the preparation of immobilized structures (for reviews on polymer-supported organocatalysts, see [201—204], for a more recent example, see also [205]). In this field, Kocovsky s group has also reported interesting Lewis base supported catalysts for the efficient asymmetric hydrosilylation of ketimines with silane 2. The first reported example was an N-methylvaline-derived Lewis basic formamide anchored to a polymeric support with... 

In addition, the asymmetric reduction of A7-aryl ketimines with tri-chlorosilane could be achieved on polymer-supported organocatalysts by Kocovsky et alP Indeed, 7V-methylvaline-derived formamide anchored to a polymeric support, used at a catalyst loading of 15 mol %, allowed good enantioselectivities of up to 82% ee combined with good yields to be obtained for the formed chiral amines (Scheme 8.3). This novel methodology simplified the recovery of the catalyst, which could be reused at least five times without any loss of the activity. The best results were obtained with the catalysts directly attached to the polymer or via a suitable spacer. A strong influence of the solvents on the catalytic performance was observed with chloroform giving the... 

Scheme 8.3 Reductions of 7V-aryl ketimines catalysed by polymer-supported organocatalyst.

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