Preparation And Asymmetric Reaction Of Functionalized Silicon - Based Heterogeneous Catalysts

Silicon-based mesoporous nanomaterials have been widely used in the area of catalysis as its advantage such as high specific surface area, stable physical and chemical property, adjustable and well-organized pore chanal and surface which is easy to modify. With these merits, this kind of nanomaterials can not only has the ability of homogeneous catalysts, but many advantages homogeneous catalysts do not have through decorating the surface of nanomaterial with chemical ways and utilizing the chiral microenvironment. Consequently, the decorated nanomaterials was used as heterogeneous catalysts in asymmetric catalysis of organic reaction and make an great progress for the green and atom economic chemistry.In this paper, three kinds of functioned silicon-based mesoporous catalysts have been prepared successfully. Then we have used them in asymmetric catalysis to explore their catalytic activities.(1) With the hexadecyl trimethyl ammonium bromide(CTAB) being the template, we combined the fluorescent silica source and TEOS(tetraethoxysilane) together by copolymerization to produce the fluorescent inner core. Then, the functional chiral silica source(S, S)-4-(trimethoxysilyl) ethyl) phenylsulfonyl-1, 2-diphenylethylenediamine and bis(triethoxysilyl)ethane were used to produce the shell of the catalyst. The surfactant template was removed by refluxing in ethanol and next the collected solids were used to coordinate with [(mesitylene)Ru Cl2]2 to prepare the eventual catalyst. After testing the catalytic activity in asymmetric transfer hydrogenation, we found that the catalysts showed great catalytic activity with high conversion(con:99%) and enantioselectivity(ee:97%). It is adequately sensitive for marking the recovery of the catalyst and can also be reused for about six times with consistent catalytic activity which is more economic and green toward environment.(2) Using the hexadecyl trimethyl ammonium bromide(CTAB) as the template,(3-(triethoxysilyl) propan-1-amine) and TEOS(tetraethoxysilane) were delivered to inner catalysis core by copolymerization. Next, TEOS was dropped to form the middle shell. Thirdly, 3-(triethoxysilyl) propane-1-thiol and bis(triethoxysilyl)ethane were added to form catalytic shell. Consequently, 3-((3, 5-bis(trifluoromethyl) benzyl) amino-4-((((1R)-(6-methoxyquinolin-4-yl)(5-vinylquinuclidin-2-yl)methyl)amino)cyc lobut-3-ene-1,2-dione was linked with thiol of HS-functionalized shell by click reaction to prepare the chiral heterogeneous catalyst. After testing its catalytic activity in chiral Henrt-Michael addition tandem reaction, we got high conversion(99%) and high enantioselectivity(99%) and there was almost no byproduct during reaction because of the spatial isolation of two catalytic sites. These catalysts can also be reused for about four times which is satisfied for the green chemistry and atom economic chemistry.