| Enlightened by the catalytic action of metal enzyme, researchers anchored the catalytically active components on the polymer containing some kinds of ligands, thus prepared a new kind of catalyst-polymer metal complex catalyst. In general, polymer metal complex catalysts have high catalytic activity, selectivity and stability. At the same time, they can be easily recovered, reused and have little causticity for equipments. In some aspects, they simulated and showed some characters of metal enzyme. For these reasons, polymer metal complex catalysts have always been paid great attention by researchers on catalysis. Chitosan is the natural polymer containing -NHi and -OH groups which can coordinate with metal ions. These complexes can be used as catalysts in many reactions, such as hydrogenation, polymerization, oxidation etc. Heck reaction, a palladium-catalyzed carbon-carbon bond formation between aryl halides and olefins, had become an excellent strategy in modern synthetic chemistry.At first, we made a detailed review of the recent progress about catalysis of chitosan complexes and the general research of Heck reaction in this thesis. According to the corresponding literatures, the chitosan-immobilized metals complexes used as catalysts had been researched, but chitosan-immobilized palladium complex used for Heck reaction has never been reported. Secondly, the chitosan-immobilized palladium complex catalyst was prepared and characterized. Thirdly, the catalytic performance of this catalyst in Heck reaction was studied. At last, chitosan-immobilized copper, cobalt, nickel and ruthenium complexes were prepared and their catalytic performances in the Heck reaction were investigated. In conclusion, a green heterogeneous catalyst which had high activity and stereoselectivety for Heck reaction-chitosan-immobilized palladium complex was prepared. This catalyst offered some practical advantages, such as easy preparation, separation from the reaction mixture and reuse. The results were as following:1. Preparation and characterization of chitosan-immobilized palladium complex.(1) Chitosan-immobilized palladium complex was prepared by different methods. According to the results of experiments, the catalytic performances of these catalysts were similar. Among of them, the simplest preparation method was as following: stirring ethanol solution of PdCl2 with chitosan in flask at room temperature, the yellow solid was then filtered and washed fully with ethanol; the yellow powder was suspended in ethanol and refluxed under nitrogen atmosphere, then the solid was filtered and dried.(2) The catalysts were characterized by FTIR, XPS, XRD and TG-DTA. The results showed that Pd particles were immobilized on chitosan.(3) The structure of chitosan-immobilized palladium complex catalyst was proposed:(4) Palladium content in the catalyst was 2.0 wt. %. 2. Studies on catalytic performance of chitosan-immobilized palladium complex in Heckreaction.(1) Heck acrylation of iodobenzene with acrylic acid: Effects of the molar ratio of Arl / AA, the base and its amount, reaction temperature, reaction time and the amount of catalyst on the reaction were investigated. The results show that the optimal reaction conditions are: 10 mmol Arl, 1 : 1.5 molar ratio of Arl / AA, 25 mmol Et3N, 0.05 g chitosan-immobilized palladium catalyst, 6 mL DMF, 80 C for 5 hours. Under these conditions, the cross-coupling of iodobenzene with acrylic acid can be achieved 93.3 %yield of frara'-cinnamic acid.(2) Heck arylation of iodobenzene with butyl acrylate: Effects of the molar ratio of BA / ArI, Et3N / Arl, reaction temperature, reaction time and the amount of catalyst on the reaction were investigated by orthogonal designation method. The sequence of the effect of the above factors is: reaction temperature > the molar ratio of BA / ArI > the molar ratio of EtsN / Arl > the amount of catalyst > reaction time. Under the optimal reaction conditions: 5 mmol ArI, 1 : 1 molar ratio of Arl and butyl acrylate, 9 mmol EtsN, 0.1 g catalyst, 3 mL D... |
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