Preparation Of Pd/Sep,Pd,Ag~+/Sep And Their Properties In Suzuki Coupling Reaction

Sep(Sepiolite)is a fibrous porous magnesium-rich silicate mineral clay,which can absorb a large number of molecules or precious metal ions,and has a good application prospect in catalyst carrier.Suzuki coupling reaction between arylboronic acid and halogenated aromatics catalyzed by Pd is an effective method for the synthesis of aromatic compounds.It is widely used in pharmaceutical intermediates,organic functional materials,natural products and engineering materials.However,Pd is expensive and difficult to recover,and the separation and treatment of Pd/Sep,Pd,Ag+/Sep is simple and convenient for repeated use,which is also consistent with the development trend of green chemistry.In this paper,the research mainly includes the following aspects:1.The application of Sep in the field of catalyst carrier,the preparation and modification of supported catalyst,the introduction of Suzuki coupling reaction and some application is summarized in recent years.2.Orthogonal test is used to optimize the conditions of hot and acid modification of Sep:HNO3 concentration 1.2 mol/L,solid-liquid volume ratio 1:15,time 10 h,temperature 60?,and calcined at 250? for 4 h to stable the active center.After determing the optimization conditions,Pd/Sep,Pd,Ag+/Sep catalysts are prepared by impregnation method.3.Suzuki coupling reaction between bromobenzene and aryl boronic acid catalyzed by Pd/Sep is studied:Seven kinds of biphenyl compounds have been obtained by K2CO3 as base,MeCN/H20(1:1)as solvent,110?,24 hours and a desired yield is obtained.The results show that the reaction between bromobenzene and phenylboronic acid,4-tert-butylbenzeneboronic acid,4-carboxyphenylboronic acid or 3-nitrophenylboronic acid,the yield of biphenyl compounds is obtained from 70%to 80%,which is relatively high,while catalying the reaction between bromobenzene and 4-ethyl benzene boric acid,4-methylthiophenylboronic acid,3,4-difluorobenzene boronic acid,the yield is relatively low,only 60%or less.Moreover,the activity is greatly reduced,and the deactivated Pd/Sep is directly calcined at 250? for 4 h to recover its activity and it doesn't decrease significantly after six cycles.4.Suzuki coupling reaction between chlorobenzene and aryl boronic acid catalyzed by Pd,Ag+/Sep is studied:Fourteen kinds of important biphenyl compounds can be obtained by NaAc as base,MeCN/H20(1:1)as solvent,90?,12 hours and the relatively desired yield is obtained.The results show that the yield of biphenyl compounds obtained in Suzuki coupling reaction involved chlorobenzene is not more than 40%,while the reaction of 3-fluoroiodobenzene and 3-fluoroiodobenzene catalyzed by Pd,Ag+/Sep,the gas phase yield of biphenyl compounds is more than 80%,and isn't affected by the electron effect.In the Suzuki coupling reaction involved 4-chloroiodobenzene,the first catalytic activity performs well,but is seriously inactivated after repeated use.The deactivated Pd,Ag+/Sep is irradiated under visible light,and after the degradation of AgI,the catalyst is centrifuged from the aqueous solution,then washed three times and dried at 150? for 4 h to recover its partial activity.The results show that Sep has been modified under optimized conditions,the reaction can be effectively catalyzed by Pd/Sep,Pd,Ag+/Sep,and they can be recycled under a certain treatment,which reduce the amount of precious metals palladium's waste and improve the economic benefits.