Preparation And Application Of Polymer-supported Catalysts

Polymer-supported catalysts have gained wide interest in recent years in organicsynthesis. This is primarily because polymeric catalysts can expand the range ofapplicaable solvents, provide convenience of work-up and product purification, lowerthe environmental hazards, and in most case provide for recovery and reuse ofpolymer supported reagent without or after regeneration. It is well known thatpoly(vinyl chloride) (PVC) is widely used inexpensive and easily modified byfunctional group via displacement reaction directly without chloromethylation makesits suitable polymeric supports for heterogeneous catalyst. To development ofprepared protocols and application of PVC supported catalysts, we explore thecatalytic activities of functionalized PVC immobilized the catalytically activepalladium nanoparticles; the PVC supported ionic liquids and the PVC supportedtetraethlenepentamine (abbreviated as PVC-TEPA) in this thesis. This thesis isdivided into four chapters.In chapter 1, one briefly introduce about the characters and synthesis of thepolymer-supported catalyst and the polymer-supported ionic liquids, as well as theirapplication in Heck and Biginelli condensation.In chapter 2, we have attempted to prepare and character the functionalizedpolymer of PVC supported 2-aminoethanol (abbreviated as PVC-AE) and further useit as support to immobile palladium nanoparticles. Experimental results demonstratedthat the as-prepared catalyst provides the active and recyclable heterogeneouscatalysts for the Heck type carbon-carbon bond formation reaction in the absence ofphosphine ligands under the air and moisture with excellent yields. Under the samereaction condition, prolonged time and high yields were observed when use the ionicliquid [bmim]BF₄ and [bmim]PF₆ as reaction media. The catalyst was easily recoveredby simple filtration and reused for 6 times cycles.In chapter 3, An improved protocol for the Biginelli reaction using poly(vinylchloride) supported ionic liquid as a reusable catalyst is described. The synthesis of 3, 4-dihydropyrimidin-2(1H)-ones was achieved under solvent-free condition.After separation of product from the reaction mixture, the catalyst was recoveredand reused for 5 times without any loss of activity.In the last chapter, we reported the classical Knoevenagel condensation catalysedby poly(vinyl chloride) supported tetraethylenepentamine (PVC-TEPA). The catalystreported here is an attractive addition to existing methodologies, since the reaction israpid, the yields are excellent, the procedure is simple, the catalyst can be recoveredand reused.In summary, the reactions and the synthetic methods mentioned above possesssuch advantages as readily available starting materials, mild reaction conditions,simple operation, high selectivity, high yields, environmentally benign and thepotential for recycling of catalysts.