Preparation Of Polyphase Asymmetric Epoxidation And Chiral Cyclic Carbonates

Silica material has wide range of applications in production and life, however, integration of periodic mesoporous organosilica(PMO) has been less explorated.Organosilica also has many advantages, it is simple to prepare and has remarkable thermal and mechanical stability. Terminated by silanol group and one or more organic functional group on the surface of it which in favor of loading various catalysts.What’s more, the superior hydrophobicity of this backbone layer can be benefit for the transmission of reactant which may enhances significantly the catalytic activity. After the reaction, catalyst can be recovered easily by filtration. With the exacerbation of Greenhouse effect, how to recycle carbon dioxide effectively are major issues related to the survival of mankind and the environment. As a renewable resources, use carbon dioxide as raw material to synthesize cyclic carbonates undoubtedly have positive significance. Asymmetric catalysis can be divided into two kind of typical types(except for enzyme) which use the transition metal or small organic molecules as catalysts.Based on those backgrounds,we design a organo-silica material as carrier to support small organic molecules catalyst to catalyzed asymmetric epoxidation and use transition metal catalyst to get asymmetric cyclic carbonate.(1) In this issue, 1,2-Bis(triethoxysilyl)ethane and 3-Mercaptopropyltriethoxysilane are used to get a mesoporous organosilica material by copolymerization in water. Hexadecyl trimethyl ammonium bromide was used as template. There are lots of thiol group in the surface of the material, which can carry on click reaction with carbon-carbon double bond. From the result of catalysis for the reaction of asymmetric epoxidation reaction of trifluoromethyl chalcones, heterogeneous catalyst 3 has a nice catalytic activity and retain a high enantiomeric excess(ee > 90 %) values. After reaction, catalyst can be recovered easily by using centrifugation and the catalyst can be reused for at least 8 times without loss of its catalytic activity. After that, we use the production to get on a ring-opening reaction and also retain a high enantiomeric excess.(2) In the second issue, complexation of(Cp*RhCl2)2 with TsDPEN is used as a catalyst to prepare chiral 1-Phenyl-2-Bromoethanol then to get asymmetric styrene oxide with NaOH which can generate cyclic carbonate with stereoselectivity in the environment of carbon dioxide(1 atm). From the result of the reaction, transition metal catalyst has a nice catalytic activity and retain high enantiomeric excess(ee) values, reactionsystem compatibility is perfect. Recycle and reuse carbon dioxide accord thebasic requirements of green chemistry.