Study On The Fe₃O₄Nanoparticles Supported Cu（I）/hb-PAMAM Complexes For The C-N Coupling Reaction

Ullmann reaction is one of the most important methods to construct C-C, C-N, C-S and C-O bonds in organic synthesis. In the past decades, the research on Copper-catalyzed C-N coupling reaction has achieved considerable progress, including the reaction in the presence of ligands, the reaction by using of water as solvent, and the reaction without the use of solvent. However, few studies on the reuse of catalyst were reported. Fe3O4nanoparticles have emerged as robust and high-surface-area heterogeneous catalyst support in a variety of reactions due to the easiness of separation from the reaction mixture by an external magnet. While, their applications in C-N Ullmann coupling reaction have not been reported.In addition, hyperbranched polyamidoamine (PAMAM), due to the abundant functional groups, exhibits excellent chelating capacity for metal ions. Therefore, in this thesis, PAMAM was grafted onto Fe3O4surface to produce a new type of catalyst support, which could be used as ligand simultaneously. This catalyst support was applied in the C-N coupling reaction to achieve a high catalytic efficiency and recycling of the catalyst.In this thesis, magnetite particles (Fe3O4) were prepared by a reduction-precipitation method with FeCl3as an iron source and Na2SO3as reductant. The Fe3O4was characterized by X-ray powder diffraction (XRD). The average diameter of the magnetite nanoparticles is394.5nm. The Fe3O4nanoparticle was modified by3-aminopropyl trimethoxysilane (APTS) to prepare magnetite nanoparticles coated with3-aminopropyl trimethoxysilane (Fe3O4-APTS). Fe3O4modified by hyperbranched polyamidoamine (named as Fe3O4-hb-PAMAM) was prepared via a one-pot polycondensation of AB2type monomers on the surface of magnetite particles, which was modified with silane coupling agent containing amino group and hence could initiated the polycondensation. Fe3O4-hb-PAMAM was characterized by infrared spectrum (IR), thermal gravimetric analysis (TGA) and transmission electron microscope (TEM). The organic content in Fe3O4-hb-PAMAM dendrimers is13.37%, confirming that hb-PAMAM dendrimers has been linked to the surface of Fe3O4. The weight losses at200℃for Fe3O4-hb-PAMAM dendrimers is4.16%, indicating that these compounds exhibit good thermal stability at200℃,Fe3O4-hb-PAMAM coordinated with CU2O to form the Fe3O4nanoparticles supported Cu(Ⅰ)/hb-PAMAM complexes. The complex was employed to catalyze the C-N coupling reaction of aryl halides with imidazole at95℃and showed high efficiency toward various aryl halides and given products in good yields up to98%. Various functional groups of aryl halides were compatible in this catalyst system. When the Fe3CO4nanoparticles supported Cu(I)/hb-PAMAM complexes was used to catalyze the C-N coupling reaction of aryl halides with benzylamine. the presence of electron-withdrawing groups on the aryl halide molecular could improve the reaction efficiency. Furthermore, the catalytic system is not sensitive to air. Some reactions have successfully been performed in air, which simplify the procedures.The Fe3O4nanoparticles supported Cu(I)/hb-PAMAM complexes can be quickly recovered by simply applying a magnet and reused for six runs without significant loss in catalytic activity. In the process of recycling, with fresh Fe3O4-hb-PAMAM and copper source added to the recovered catalyst, the yield can be maintained at stable level (94%-97%). In conclusion, we have realized the recycling of the catalyst in C-N coupling reaction.