For The Heck Reaction, Pd / Natural Polymer Catalyst Preparation, Characterization And Performance Study

Chitosan(CS)-ferrocenylimine palladacycle, konjac glucomannan(KGM) and collagen(CG)-supported Pd catalysts were prepared and characterized by the different analytic methods. The preparation of these catalysts is rather simple and convenient, and they are environmentally benign catalysts because of the biodegradability and non-toxicity of these biopolymers. These catalysts not only have high activities in the Heck reaction, but also offer practical advantages such as easy handling, separation from the product and reuse for several times with keeping the high activity. Studies on these nature polymer supported palladium catalysts not only have the scientific significance but also offer us the feasibility of potential applications.1. Preparation and characterization of CS-ferrocenylimine palladacycle catalyst and its catalytic activity in Heck reaction(1) The preparation and characterization of CS-ferrocenylimine palladacycle catalyst. CS-ferrocenylimine palladacycle catalyst was synthesized from chitosan and ferrocenecarboxaldehyde via grafting to form CS-ferrocenylimine, followed by reacted with Li₂PdCl₄ in methanol. Chitosan, CS-ferrocenylimine and CS-ferrocenylimine palladacycle catalyst were characterized with IR, XRD, TG-DSC, UV-Vis, fluorescence spectrophotometry and XPS. According to the results of analysis, the structure of CS-ferrocenylimine palladacycle catalyst was proposed.(2) Study on the catalytic performance of CS-ferrocenylimine palladacycle catalyst in Heck reaction. First, the reaction of iodobenzene (PhI) with acrylamide(AM) was studied. Effect of different reaction conditions (kinds and amount of base, reaction temperature, solvent, molar ratio of iodobenzene to acrylamide, amount of catalyst and reaction time) on the yield of cinnamamide was investigated. The appropriate conditions for the reaction were established as follows: PhI: 10.0 mmol, Et₃N as base, n_PhI: n_AM:n _Et3N = 1:1.1: 2.0, catalyst 0.025 g, solvent DMF 4 mL and 100°C for 30 min. Under the above conditions, the yield of cinnamamide was 97.3%. The catalyst was recycled up to five times still with the good catalytic activity, and the yield of 88.0% in the 5^th recycle was still achieved. The other Heck reactions were also investigated, and the product yields are more than 84.7%.2. Preparation and characterization of KGM-Pd catalyst and its catalytic activity in Heck reaction (1) The preparation and characterization of KGM-Pd catalyst. KGM-Pd catalyst was synthesized by the reaction of KGM with PdCl₂ in ethanol, and characterized with IR, XRD, TG-DSC and XPS. The results indicated that the coordination bonds are formed between O of KGM with palladium.(2) Study on the catalytic performance of KGM-Pd catalyst in Heck reaction. First, the reaction of iodobenzene with acrylic acid (AA) was studied. Effect of different reaction conditions (reaction temperature, molar ratio of iodobenzene to acrylic acid, kinds and amount of base, solvent, amount of catalyst and reaction time) on the yield of cinnamate were investigated. The appropriate conditions for the reaction were established as follows: Et₃N as base, PhI: 10.0 mmol, n_PhI: n_AA:n_Et3N = 1: 1.4: 2.5, catalyst 0.050 g, solvent DMF 6 mL and 100°C for 1.5 h. Under the above conditions, the yield of cinnamate was 91.9%. The catalyst was recycled up to five times without significant loss in the catalytic activity, and the yield of 89.3% in the 5^th recycle was still achieved. The other Heck reactions were also investigated, and got the yields above 82.8%.3. Preparation and characterization of CG-Pd catalyst and its catalytic activity in Heck reaction(1) The preparation and characterization of CG-Pd catalyst. CG-Pd catalyst was synthesized by the reaction of CG with PdCl₂ in ethanol, and characterized by XRD and XPS. The results indicated that the coordination bonds are formed between O and N of CG with palladium.(2) Study on catalytic performance of CG-Pd catalyst in the reaction of iodobenzene with acrylic acid. Effect of different reaction conditions (solvent, reaction temperature, molar ratio of iodobenzene to acrylic acid, kinds and amount of base, amount of catalyst, and reaction time) on the yield of cinnamate were investigated. The appropriate conditions for the reaction were established as follows: PhI: 10.0 mmol, Et3N as base, n_PhI: n_AA: n_Et3N = 1: 1.4: 2.5, catalyst 0.010 g, solvent DMF 6 mL and 100°C for 45 min. Under the above conditions, the yield of cinnamate was 94.7%. The catalyst was recycled up to three times to still achieve the yield of 88.0%.