HETEROGENIZATION OF CHIRAL RUTHENIUM CATALYSTS WITHIN SILICA MICROCAPSULES

Asymmetric catalysis in particular asymmetric hydrogenation is powerful synthetic method which is applied routinely for preparation different chiral compounds that are of central importance to the human society. Homogeneous asymmetric catalysis has been significantly advanced during the last three decades where the emphasis was to design and prepare libraries of chiral ligands in order to obtain higher enantioselectivity. At present, it becomes possible to obtain homogeneous asymmetric catalysts that exhibit excellent activity and enantioselectivity. However, the application of these expensive catalysts in industrial processes especially in pharmaceutical industry is limited due to difficulties in their separation and recycling. In order to overcome these limitations, several methods of heterogenization of asymmetric catalysts have been intensively investigated. ^[1] Although heterogenization of asymmetric catalysts could facilitate their separation and recycling, but this process led to decrease in the activity and the selectivity of the heterogenized catalysts.

In our research, we focus on developing a method for preparation silica microcapsules from oil in water emulsion system. These microcapsules are utilized in the heterogenization of chiral ruthenium catalyst functionalized with silane group. The catalyst is immobilized onto the inner side of silica shell by co-condensation between the silane funcational group of the catalyst and the silanol groups of the silica shell.

The preparation method, characterization and applications of these catalytic silica microcapsules will be presented.

References

3385. a) Q. H. Fan, Y. M. Li and A. S. C. Chan, Rev., 2002, 102, 3385. b) P. McMorn and G. J. Hutchings, Chem. Soc. Rev., 2004, 33, 108. c) M. Heitbaum, F. Glorius and I. Escher, Angew. Chem. Int. Ed., 2006, 45, 4732.