Study On Synthesis Of Chiral Phosphine-containing Metal Complex Catalysts And Their Application In Asymmetric Catalytic Reaction

Chiral metal catalysts has been attracting great attention due to the demands of industrial production. However, it is limited by the difficulty in synthesizing and the high price of the chiral catalysts. so, the problem will be resolved if the catalyst can be recycled. Based on our former work, we designed and synthesized a novel series of chiral ligands by using peripherilly alkyl-functionalized dendrimer and imidazolium salt moiety as the carrier, respectively, choosing chiral diphosphine ligand Pyrphos as the model ligand. Their catalytic properties have been studied by applicating these catalysts in asymmetric hydrogenation of dehydroamino acids. and on this basis, the recycle of catalysts have been studied. The main contents included are as follows:1. A series of chiral pyrphos-functionalized with alkyl chains at the periphery of the dendrimer have been synthesized and characterized, then applied their rhodium complexes in the asymmetric hydrogenation of dehydroamino acids. The influence of reaction medium, reaction temperature, reaction time, the structure of catalyst and the molar ratio of substrate to catalyst on the catalytic activity and enantionselectivity have been investigated. The study of recycle of catalyst in the mixed solvent of cyclohexane– methanol has been researched on the optimized conditions. It was found that these dendrimer catalysts gave high activity and enantionselectivity, which were comparable to those obtained from the corresponding homogeneous catalysts. The separation and recycle of the catalyst in the mixed solvent of cyclohexane– methanol exhibited excellent by adding some water, but the Rh- catalyst has a certain extent solubility in methanol, which results in losing of some catalyst by recovering these catalysts and affecting the catalytic properties.2. The method of synthesizing a novel task-specific chiral pyrphos, which functionalized by an imidazolium salt moiety, has been studied, and its catalytic activity and recyclability for asymmetric hydrogenation of dehydroamino acids was examined.