Preparation And Properties Of Silica - Loaded Polymer Supported Supported Chiral Metal Catalysts

Siloxane-organic hybrid materials, assembled by polyhedral oligomeric silsequioxane(POSS) units, represent a new class of hybrid silica materials with particularly attractive features in asymmetric catalysis that has not been recognized yet. Unlike traditional mesoporous silica materials, these hybrid materials have many outstanding advantages. First, they embody both organic–inorganic characteristics and cagelike structures in one small nanoentity. Second, unique POSS cavum provides additional channels to transport reactants and products and can facilitate a high efficient catalytic reaction. Third, taking advantage of POSS vertex groups as a functionalized bridge, it is also convenient to introduce various desired functionality onto their frameworks, which can be applied in the field of asymmetric catalysis. Last but not least, the structural diversity of vertex functionality allows modifuing various hydrophobic/hydrophilic groups onto POSS frameworks, which opens up new possibility to tailor its surface physico-chemical properties according to the requirements of application. Owing to the potential advantages of these materials, This paper is divided into two parts:The first part: Both polyhedral oligomeric silsequioxane(POSS) and triethoxy silane(HSi(OEt)3) are addition reaction to generates POSS silicon source, and then 10% mo L(S,S)-Ts DPEN silicon source and Ethyl silicon source copolymerization to generate functional material of POSS and then added [Cp * Rh Cl2] 2 to produce heterogeneous catalyst 。Then we prepare a hydrophilic heterogeneous catalysts through the method of chemical click to graft Quaternary ammonium salt.and then test it in water system of aromatic ketosteroid asymmetric catalytic. Then, we study the catalytic activity and enantioselectivity on asymmetric transfer hydrogenation reaction in aqueous phase. The experimental results show : First, Compared with the unmodified heterogeneous catalyst, we find that the dispersion of modified catalyst in the water is much better and the speed of catalytic reaction is much faster. Last, it could be easily recovered. After it is used 8 times repeatedly, the catalytic activity and selectivity is not obviously reduced.The second part: We choose cetyl-trimethylammonium tosylate(CTATos) as template, TEOS as a main silicon source, 10 % POSS and 10 % Ts DPEN as a functional silicon source and graft Rh metal to produce a chrial heterogeneous catalyst with the framework of silicon-oxygen- silicon and then test it in water system of aromatic ketosteroid and cyclic amine asymmetric catalytic. We study catalysts in the ethyl acetate solution respectively with formic acid triethylamine(5:2) as the hydrogen source, respectively for 4,5-diaryl cyclic sulfamidates asymmetrically transfer hydrogen reaction preparing double chiral amine or 4- aryl amine preparing mono chiral. The experimental results show that the heterogeneous catalysts present high catalytic activity and enantioselectivity. Furthermore, it could be easily recovered. After it is used 8 times repeatedly, the catalytic activity and selectivity is not obviously reduced.