Synthesis And Application Of Silsesquioxane Assembled Organic Metal Catalyst

Siloxane-organic hybrid materials, assembled by polyhedral oligomericsilsequioxane (POSS) units, represent a new class of hybrid silica materials withparticularly attractive features in asymmetric catalysis that has not been recognizedyet. Unlike traditional mesoporous silica materials, these hybrid materials have manyoutstanding advantages. First, they embody both organic–inorganic characteristicsand cagelike structures in one small nanoentity. Second, unique POSS cavumprovides additional channels to transport reactants and products and can facilitate ahigh efficient catalytic reaction. Third, taking advantage of POSS vertex groups as afunctionalized bridge, it is also convenient to introduce various desired functionalityonto their frameworks, which can be applied in the field of asymmetric catalysis. Lastbut not least, the structural diversity of vertex functionality allows modifuing varioushydrophobic/hydrophilic groups onto POSS frameworks, which opens up newpossibility to tailor its surface physico-chemical properties according to therequirements of application. Owing to the potential advantages of these materials,This paper is divided into three parts:The first part: We choose CTAC as template, TEOS as a main silicon source,10%POSS and10%TsDPEN as a functional silicon source and graft Rh metal to produce achrial heterogeneous catalyst with the framework of silicon-oxygen-silicon. We studyits catalytic activity and enantioselectivity on asymmetric transfer hydrogenation ofaromatic ketones in aqueous phase. The experimental results show that theheterogeneous catalysts present high catalytic activity and enantioselectivity.Furthermore, it could be easily recovered. After it is used8times repeatedly, thecatalytic activity and selectivity is not obviously reduced.The second part: We choose P123and CTAB as template, POSS as a main siliconsource,10%Ts-DPEN as a functional silicon source and graft Ru metal to producetwo chrial heterogeneous catalysts with the framework of POSS. One posseses thestructure of two-dimensional six party and another3D flowerlike mesoporous silica materials. Then we prepare a hydrophilic heterogeneous catalysts through themethod of chemical click to graft PEG. Then, we study the catalytic activity andenantioselectivity on asymmetric transfer hydrogenation reaction in aqueous phase.The experimental results show: First, Compared with the unmodified heterogeneouscatalyst, we find that the dispersion of modified catalyst in the water is much betterand the speed of catalytic reaction is much faster. Second, these two catalysts bothpresent high catalytic activity and enantioselectivity not only on asymmetric transferhydrogenation reaction of aromatic ketone but also quinoline. Last, it could be easilyrecovered. After it is used8times repeatedly, the catalytic activity and selectivity isnot obviously reduced.The third part: According to the synthesis method in second part, we synthesistwo different heterogeneous catalysts and study the other two asymmetricadditional reaction, which are the asymmetric Malonate Addition of Nitroalkenes andthe asymmetric transfer hydrogenation of cyclic imines, exhibiting excellent catalyticactivity and enantioselectivity. We successfully expand the catalytic reaction system.