A Heterogeneous Palladium-ruthenium Bifunctional Catalyst Was Used For Asymmetric Series Reaction Studies Of Coupling/reduction

Recently,more and more researches and experiments have been done on multiple-step organic transformations in one-pot catalytic process,and many heterogeneous bifunctional catalysts have come into being.The production of heterogeneous bifunctional catalysts have attracted a great deal of interest due to atomic economy and minimum workup.It can not only overcome the difficulty of the cyclic utilization of catalyst,but can also overcome the difficulty of the loss of noble metal,which help to solve the problem of the heavy metal pollution.The selection of the carrier material of heterogeneous catalyst has great effect on the catalytic reaction.Organsilica-based mesoporous materials as supports to immobilize organometallic complexes and metal particles have exhibited some attracting features in catalysis.And the mesoporous organosilica nanoparticles with dendritic-like and serface on serface morphology have a relatively short medium distributed cavity and the special silicate cavity.Because of the unique characteristics,it has been widely applied in the field of catalysis.In this paper,two kinds of functional silicon-based mesoporous catalysts have been prepared successfully.Then we had used them in asymmetric catalysis to explore their catalytic activities.(1)With the methyloxiranepolymerwithoxiraneblock(P123)being the template,we combined bis(triethoxysilyl)ethyl,3-mercaptopropyltriethoxysilane and the functional chiral silica source(S,S)-4-(trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine together by copolymerization to produce the periodic mesoporous organosilica materials.The surfactant template was removed and next the collected solids were used to coordinate with palladium chloride.The product was stirred with NaBH4 solution to prepare the Pd nanoparticles.Then the collectd solids were used to coordinate with [(mesitylene)RuCl2]2 to prepare the Pd/Ru-bimetallic catalyst.It realized a tandem reaction from Ru-catalyzed asymmetric transfer hydrogenation to Pd-catalyzed Sonogashira coupling and Suzuki coupling in one-pot process.After testing the catalytic activity in cooperatively tandem coupling-asymmetric transfer hydrogenation of haloacetophenones and arylacetylenes or arylboronic acids,we found that the catalysts showed great catalytic activity with high conversion(con: 99%)and enantioselectivity(ee: 97%).Furthermore,the heterogeneous catalyst is also conveniently recovered and reused repeatedly for at least seven times without loss of its catalytic activity.(2)A new method of synthesis of one unique novel mesoporous silica materials with dendritic-like and serface on serface morphology has been developed.The kind of catalysts is using the hexadecyl trimethyl ammonium bromide(CTAB)and sodium salicylate(NaSal)as the template,tetraethoxysilane and bis(triethoxysilyl)ethane were self-assembly in this atmosphere.In the process,functional chiral silica source ? bis((((dicyclobecy)phosphino)propyl)triethoxysilane)palladium dichloride and alkalinous silane(IT-DABCO)were added to be self-assembly.At last,the system eliminate CTAB/NaSal by MeOH-HCl and treated with ammonia(10 wt% sol.in water).We can gain a kind of trifunctional catalyst which possess dendritic-like and serface on serface morphology.After testing the kind of catalysts activity in cooperatively tandem coupling-asymmetric transfer hydrogenation of haloacetophenones and arylacetylenes,we found that the two kinds of catalysts showed great catalytic activity with high enantioselectivity(ee: 99%).The kind of catalysis can also be reused seven times which is satisfied for the green chemistry and economic chemistry.