I&EC 68 |
| There have been increasing research activities in organic catalysis, especially chiral organic catalysis, in recent years. However, organocatalysts still face some major challenges in industrial applications, such as high catalyst/substrate ratio, and difficulties in catalysts separation and products purification. These issues may be addressed with the use of solid supports. Herein, we successful immobilized a highly efficient and enantioselective organocatalyst, imidazolidin-4-one, on siliceous MCF and polymer-coated MCF. The resulting heterogenized catalyst demonstrated excellent catalytic performance and recyclability for Friedel-Crafts alkylation and Diels-Alder cycloaddition. It has been known that the silanol groups on silica surface might affect the activity of immobilized catalysts. In this work, we examined the performance of supported catalysts in relation to the surface environment of siliceous MCF. It was found that partially pre-capping the MCF with TMS groups enabled us to attain well-dispersed catalysts on the siliceous support with the optimal performance. We have also developed a polymer-coated MCF, which retained the porous structure of MCF without the surface silanol groups. High reactivity and excellent recyclability were achieved by the organocatalyst immobilized on polymer-coated MCF. The new approaches described in this paper allowed us to manipulate catalyst enantioselectivity, activity and recyclability through the careful modification of the MCF surface, and the modulation of the microenvironment surrounding the anchored catalysts. |
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Green Chemistry and Engineering Poster Session
8:00 PM-10:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Sci-Mix
Division of Industrial & Engineering Chemistry |