The Application Of Polyethylene Glycol Functionalized Silicon-based Catalysts In Coupling-reduction And Addition-reduction Reactions

Organic reactions in one-pot catalytic process,due to atomic economy and minimum workup,have attracted a great deal of interest.However,intrinsic disadvantages of reuse of expensive organometallic complexes and product contamination still hinder practical applications in industrial process.Thus,immobilizing two kinds of or more organometallic into Silica-based mesoporous materials could overcomes the above drawbacks.The heterogeneous catalysts have the advantages of easy to be prepared,easy to be recycled,and are environmentally friendly,and have been the focus of chemical researchers in recent years.However,the heterogeneous catalysts often show the disadvantages of agglomeration,wall sticking and bad dispersivity in the solvent.Therefore,the focus of the research on the supported catalyst lies in the innovation and improvement of the carrier.We have synthesized a kind of polyethylene glycol modified dendritic silica precursors?PEG-PEOS?through the reported work,and made use of the characteristics of PEG terminal modification to self assemble into mesoporous materials.Then,synthesizing heterogeneous catalysts with other functions apply to organic transformations.Due to the modification of PEG goups,the catalyst oweshighly dispersed feature in the aqueous solvent,and it can greatly promote the reaction transformation and shorten the reaction time.This is of special significance for the traditional heterogeneous.And it can be applied to replace many polluted organic solvents by the green solvents.This paper mainly divided into the following two parts:?1?Preparation of vesicular palladium-ruthenium supported metal catalyst modified by polyethylene glycol and its application in Suzuki-Miyaura coupling/reduction tandem reaction.First,we synthesized hydrophilic dendritic silica precursors PEG20-PEOS?20 on behalf of PEG to replace the terminal-OEt groups,and then adding proportion?and we take use of a self–templating approach and develop a bifunctional heterogeneous catalyst over a three–component self–assembly,where dual palladium/phosphine–and chiral ruthenium/diamine–functionality are assembled conveniently within poly?ethyleneglycol?monomethylether–modified hyperbranched polyethoxysiloxane oobtained vesicular bifunctional catalyst.This catalyst can catalyze Suzuki-Miyaura coupling reaction and asymmetric hydrogen transfer cascade reactions with up to 99%yield and 97%enantioselectivity.Furthermore,the heterogeneous catalyst is also conveniently recovered and reused repeatedly for at least seven times without loss of its catalytic activity,presenting a practical organic transformation in one-pot manner.?2?Preparation of polyethylene glycol modified hollow sphere bifunctional organic base-ruthenium supported metal bifunctional catalyst and its application in Michael addition/Asymmetric hydrogen transfer reaction.We also synthesized hydrophilic dendritic silica precursors PEG10-PEOS and utilize the feature of self-assemble to fabricate hydrophilic hollow sphere nanoparticles?DABCO@ArDPEN@HMSNPs?incorporated with organic base-and ruthenium/diamine–functionality.Then,coordinated with[RuC l₂?mesitylene?]₂ preparation of polyethylene glycol modified hollow shell organic base-ruthenium bifunctional supportedmetalcatalysts.?DABCO@Mesitylene RuArDPEN@MHSNPs?The hydrophilic bifunctionalized catalysts realize a tandem reaction in one-pot process for the synthesis of?-amino alcohols with up to 97%yield and 97%enantioselectivity,Furthermore,the heterogeneous catalyst is also conveniently recovered and reused repeatedly for several times without loss of its catalytic activity.