Study On The Application Of Polymer-supported Catalysts In Organic Synthesis

Polymer-supported catalysts have high stability, low corrosion, and easy to be recovered from the reaction system and reused. Therefore, polymer-supported catalysts have important academic and industrial applications, due to their high catalytic activities and selectivities. It is well known that poly(vinyl chloride) (PVC) is a widely used inexpensive and easily modified by functional group via displacement reaction directly without chloromethylation makes its suitable polymeric supports for heterogeneous catalyst. We explored the catalytic activities of palladium nanoparticles immobilized on the functionalized PVC in this thesis. This thesis is divided into four chapters.In chapter 1, one briefly introduce about the characteristics of polymer-supported catalysts, as well as their variety and application in organic synthesis.In chapter 2, we have prepared and character the functionalized polymer of PVC-supported Schiff base (abbreviated as PVC-EDA-SA) were prepared from PVC with sequential attachment of ethylenediamine and salicylaldehyde and further use it as support to immobile palladium nanoparticles. The as-prepared catalyst was found to be air and moisturestable and to have significant catalytic activity in Suzuki-Miyaura reactions under mild operating conditions. Various phenyl halides were coupled with phenylboronic acid in aqueous ethanol, under air, to afford the corresponding cross coupled products in good yields. Furthermore, the catalyst can be easily recovered by simple filtration and reused for up to five cycles without losing its activity.In chapter 3, we used the as-prepared PVC-EDA-SA-Pd0 catalyst mentioned above to continue to explore its catalytic performance in Heck reactions. The results showed that excellent yields obtained from DMSO, the catalyst can be reused for six times.In the last chapter, on the polymer surface of poly(vinyl chloride) supported a bulky, inexpensive and simple bidentate ligand 2-mercaptobenzothiazole (PVC-MBT) were achieved by a simple procedure. The as-prepared catalyst (PVC-MBT-Pd0) was found to be air and moisture stable and exhibits significant catalytic activity for Suzuki-Miyaura reactions under milder operating conditions. The catalysts showed excellent activity towards Suzuki coupling reaction of different aryl iodides and bromides with phenyl boronic acid using ethanol as solvent in short reaction time. Furthermore, the catalyst can be easily recovered by simple filtration and repeatedly reused for at least 5 cycles with comparable yields. In summary, the synthetic methods mentioned above possess the advantages such as catalysis can be readily prepared, mild reaction conditions, simple operation, high selectivities, excellent yields, and moreover, the potential for recycling of catalysts is benign to environment.