Cocatalysts Supporting Piperidine Radicals And Chiral Diamine Rhodium Were Used For The Study Of Secondary Alcohol Redox Reactions

In recent years,relative to the high efficiency of homogeneous catalysis,researchers have gradually focused on how to realize the recycling of efficient catalysts.So heterogeneous catalysis came into being.Researchers have made further exploration on heterogeneous catalysts.With the continuous development of science,scientists put forward higher requirements for heterogeneous catalysis: whether to use the inherent space separation of heterogeneous carrier to eliminate or avoid the conflict between two or more homogeneous catalysts as far as possible,so as to achieve the chemical reaction that homogeneous catalyst can not complete has become a research hotspot.In this paper,two kinds of functional silicon-based catalysts with different hydrophilicity and hydrophobicity were designed to form a Co-catalytic system to explore one pot series redox reaction.The main research contents are as follows:1)We have synthesized two types of silicon-based catalysts: the first is a kind of inorganic silicon spheres with uniform size distribution,which is synthesized by traditional hydrothermal method,using surfactant,cetyltrimethylammonium bromide as template,tetraethyl silicate hydrolysis under alkaline conditions.Then,the surface of silicon-based materials is aminated by post grafting method,2,2,6,6-Tetramethylpiperidinooxy was loaded on its outer surface.It can be used for the oxidation of aromatic secondary alcohols;the second one is based on the previous research progress of our research group,adding functional diamine and functional silicon source in the process of ethyl bridging to synthesize an ethyl bridged mesoporous organic hollow shell sphere,which is also vinylated by post grafting,and then loaded with temperature responsive polymer,Finally,the rhodium dimer of pentamethylcyclopentadiene was attached to the catalyst through coordination bond to form a rhodium / diamine heterogeneous temperature sensitive catalyst,which can be used for asymmetric hydrogen transfer reaction of aromatic ketones.2)Firstly,the two catalysts were characterized by 29 Si NMR,13 CNMR,BET,SEM,TEM and turbidity test,which verified that the synthesized catalysts were consistent with our expectations.Secondly,we tested the single-step oxidation or reduction reaction of the two catalysts and screened the reaction conditions,and achieved good results.We used the above two catalysts to form a Co-catalytic system in the mixed phase of water and dichloromethane,which was applied to the one pot series reaction of racemic aromatic secondary alcohols The yield and EE value of chiral aromatic secondary alcohols were 98% and 99%,respectively.Good catalytic performance was obtained.Secondly,the Co-catalytic system is easy to recover and can be reused for six times without significant decrease in yield and EE value.