Functionalized Hypercrosslinked Polymers As Efficient And Recyclable Catalysts For Organic Transformations

Hypercrosslinked Polymers(HCPs)are preferred materials for the synthesis of hetergenerous catalysts because they not only possess hydrophobic orgainc skeleton,high surface area,and permanent pores,but also have the merits of excellent stability,low-cost synthesis,various monomers,and tunable pore size.On the basis of these facts,in the thesis,HCPs are used for preparing some immobilized metal-or organic-based heterogeneous catalysts,which are then utilized for catalyzing various organic transformations to parepare many useful organic molecules.The research of this thesis greatly extends the applications of HCPs in the heterogeneous catalysis.Moreover,it serves as a bridge between HCP materials and organic catalysis.1)A hypercrosslinked polymer(HCP)-immobilized ruthenium catalyst(HCP-PPh3-Ru)was prepared from benzene and triphenylphosphine through a one-step external cross-linking reaction.HCP-PPh3-Ru was found to possess high Brunauer-Emmett-Teller surface area and good thermal stability.Moreover,HCP-PPh3-Ru was used as a recoverable and effective catalyst for the synthesis of 2,4-diaryl-substituted pyridines and the cycloaddition reaction of diazodicarbonyl compounds with olefins to afford substituted dihydrofurans.In addition,a combination of HCP-PPh3-Ru and Amberlyst-15 enables us to establish a simple protocol for the direct synthesis of carbazole derivatives from diazodicarbonyl compound,alkyl vinyl ether,and indole.In all these selected reactions,the catalyst was easily recovered and reused several times without significant activity loss.2)An N-heterocyclic carbene(NHC)-copper complex supported on hypercrosslinked polymers(HCPs)was successfully synthesized through a simple external cross-linking reaction.The obtained HCP-NHC-Cu catalyst was found to possess a large BET surface area and good thermal stability.Hence,it was used as an efficient catalyst for the click reaction of halide,sodium azide,and alkyne,the Ullmann C-N coupling,and the Glaser coupling reaction.Moreover,an oxidative condensation reaction of indoles,1,3-dicarbonyl compounds and phenylglyoxal monohydrate was developed,for the first time,with the aid of the HCP-NHC-Cu catalyst,which produced various polysubstituted olefins in high yield.At the end of these reactions,the catalyst was easily recovered and reused several times without significant loss of activity.3)A task-specific hypercrosslinked polymer(HCP)with hollow spherical structure(HCP-A-B)was synthesized.The synthetic strategy successfully achieved the peaceful coexistence of antagonistic sites on microporous organic material.The acid(sulfonic acid)sites and base(amine)sites are on the shell of the hollow sphere.In the following tandem reactions,hydrolysis/Henry and hydrolysis/Knoevenagel reactions,HCP-A-B displayed excellent catalytic performance and chemical stability to water or organic solvent.The unique catalytic ability and water-stability of the HCP-A-B catalyst enables us to develop a hitherto unreported transformation of 2-ethoxyl-3,4-dihydropyran to 2-cyclohexen-l-one derivative through a tandem reaction involving a water-assisted ring-opening hydrolysis of the dihydropyran,an intramolecular aldol,and a dehydration reaction.In all these reactions,the bifunctional HCP-A-B catalyst shows excellent recyclability because the catalyst can be reused more than 14 times.4)Heterogeneous acid(sulfonic acid)and base(benzylamine)catalysts were synthesized using simple functionalized monomers through a one-step external cross-linking reaction.The direct induction and control of catalytic sites are achieved with this method.The good stability and the accurate manipulation of the catalyst structure allowed us to use the obtained polymers as a compatible and efficient acid/base co-catalyst for two one-pot tandem reactions(deacetalization/Henry and deacetalization/Knoevenagel reactions).The results demonstrate that the catalystic system not only achieve catalyst recovery and reuse,but also can adjust the ratio of solid acid and base according to the reaction requirements.Hence,the easy-to-handle method has practical applications in organic catalysis.