Preparation Of Heterogeneous Copper Catalysts Based On Cost-effective Supporting Materials By Post-grafting Method And Its Application In Organic Transformations

Immobilization of homogeneous metal complex catalysts have long been a hot topic due to its easy isolation and high recycling ability.Among all of the well investigated heterogeneous catalysts,Cu complexes are widely used in various kinds of organic transformations because of their high catalytic activities.Immobilizing homogeneous Cu complex onto the supporting materials by post-grafting method possess high flexcibility and excellent stability,thus then becoming one of the most commonly used techniques.However,very recently Vittorio Farina and Johannes G.de Vries critically reviwed the immobilization of homogeneous catalysts and pointed out they were difficult to be used in industry.This is because for a long period of time,the chemists paied lots of attention on the cost of metal catalyst but little on the supporting materials and tedious preparation predure.And in fact,the poor stability of the linker between the metal complex and supporting materials,together with the unsmooth mass transfer among the organic substrates and solid phase catalyst,limit their application to a great extent rather than the homogeneous metal catalysts.Based on this fact,utilizing the cost effective and easily avialiable supporting materials by a simple and efficient post-grafting method to design and prepare the heterogeneous metal catalysts are appealing needed.In this work,based on our previous developed organic reactions,we used cost effective silica and sodium lignosulphonate as the suitable supporting materials and prepared the highly catalytic activity heterogeneous copper catalysts.In the following investigation,we found that the as-prepared heterogeneous copper catalysts displayed excellent performance in the classical oxidation reactions,coupling reactions,multicomponent reactions,biomass high value conversion process and synthesis of nitrogen heterocycles.The newly developed immobilization technology not only increased the stability of the grafted metal complex but also utilized the synergistic effects between the supports and the metal complex.Thus the defects exist in the homogeneous catalytic system are well handled.Specifically,there are four parts in this work:(1)By post-grafting method,utilizing the ring opening reaction of HMS-SH and 2-butoxy-3,4-dihydropyrans to immobilize the 1,3-diketone fragment onto the silica material.After following ligand exchange process,the metal acetone complexes heterogeneous catalysts were obtained(HMS-DP-M).The catalysts were fully characterized and sent to catalyze organic reactions,the results indicated that 2-butoxy-3,4-dihydropyrans as dual flexible anchoring reagents and stable ligand donors enabled the as-prepared heterogeneous copper catalyst with high thermostability and catalytic activity.They not only showed excellent performance in many kinds of organic transformations but also reused several times without significant loss of activity.(2)Taking advantage of the ring opening reaction between 2-chlorine methyl phenyl-3,4-dihydropyrans and HMS-SH,the 1,3-diketone and methyl chloride were immobilized onto HMS-SH via one step of modification.Then the methyl chloride moiety was treated with butyl imidazole by quaternarization reaction whereafter 1,3-diketone coordinated with copper acetone,and gave out the bifunctional cayalyst which posses both copper acetylacetonate moiety and amphipathic ionic liquids tag.The existing of this two kind moieties increase the dispersibility and stability of the heterogeneous copper catalyst in aqueous solution thus improve the mass transfer efficientcy of the substrates and solid supports.In the following investigation,the as-prepared catalyst coluld not only promoted the A~3 and Click reaction in water but also recycled several times without significant loss of activity.(3)Sodium lignosulphonate,a waste of paper making industry,was a kind of polyanionic materials.Firstly,it was used to react with dicationic or polycationic species to generate a hydrophobic polymer via ion exchange process in water(Flocculation Process).To immobilize TMEDA fragment,the as-prepared composite was then treated with divinyl sulfone and N1,N1,N2-trimethylethane-1,2-diamine by a consecutive twice Michael addition reactions.Finally,the CuI was coordinated with grafted TMEDA fragements and the heterogeneous copper catalyst was obtained.According to the experiment results,the thereby obtained catalyst was proven to be able to enrich the alkynol component in the Glaser heterocoupling reaction of an alkynol and phenylacetylene,thus enabling the reaction to proceed well with a low substrate ratio.These results were verified by thermodynamic calculation and GC analysis.This catalytic system not only successfully avoid using an excess amount of alkenes but also utilizing the synergistic effect between the supporting material and metal catalyst.It also featured with high stability and excellent recyclability.(4)Based on the phenol–formaldehyde condensation reaction of lignosulfonate and 2-formylbenzenesulfonic acid sodium salt,the heterogeneous copper catalyst LS-FAS-Cu was prepared.After characterized by several methods,the newly obtained composites showed higher–SO3Na density than the pristine one.Thus the Cu loading got a significant improvement than before.It showed high catalytic activity for the synthesis of nitrogen heterocycle,such as indole,pyridine,isoquinoline and naphthamine derivatives.Compared with the referential catalysts,the primary catalyst could be used several times without significant leaching of the copper metal.