Construction Of Nano-chiral Metal Catalysts Based On New Polyionic Liquids

Regardless of economic and environmental protection considerations,or its potential application value(water is required as solvent to simulate biological enzymes to catalyze the synthesis of natural products and biologically active compounds,etc.).The development of chiral catalysts with excellent performance in aqueous solutions has very important theoretical significance and practical value.In this thesis,firstly,a series of novel polyionic liquids were synthesized,and on this basis,chiral ruthenium nanocatalysts and Ru-Pd chiral nanocatalysts with core-shell structure were constructed.Furthermore,these two types of chiral catalysts were applied to asymmetric synthesis reactions in the water phase.The influence of the structure and assembly state,reaction temperature,solvent and other factors of the chiral nanocatalyst prepared in the research on the catalytic activity and stereoselectivity of the catalyst were studied,and the structure-activity relationship between catalyst structure and catalytic performance were investigated,the essential laws of chiral nanocatalysts catalyzing asymmetric reactions in water were explored.This work provides a theoretical and experimental basis for the design and development of chiral catalysts with high catalytic activity and high selectivity,easy to separate and reusable in aqueous solution.The specific content is as follows:(1).Preparation of chiral ruthenium nano-catalyst based on polyionic liquid and its application in asymmetric transfer hydrogenation of alkyl ketones in aqueous phaseFirst,four new types of polyionic liquids with different anion structures were prepared by ion exchange(complete exchange or partial exchange).Then,a chiral Ru nanocatalyst with a stable structure was synthesized by the interionic interaction between the polyionic liquid and the chiral ruthenium random copolymer containing carboxylic acid groups.The element composition,structural morphology,surface affinity,hydrophobicity and thermal stability of the catalyst were further characterized.Furthermore.the prepared catalysts were applied to the asymmetric hydrogen transfer reaction of alkyl ketone in water.When polyionic liquid contained[NTf₂]^-and Cl^-,the prepared chiral Ru nanocatalyst has micelle-like properties,which can effectively enrich the reaction substrate,catalyze the alkyl ketone hydrogenation transfer reaction in the water phase with high catalytic activity and high selectivity.Polyionic liquid has the dual role of synergistic catalysis and stabilizing catalyst.The catalyst can be recycled and catalyzed 9 times,and its catalytic activity and enantioselectivity were not significantly reduced.(2).Preparation of Ru-Pd thermally responsive nano-chiral catalyst based on polyionic liquid and its efficient and selective catalysis of Suzuki coupling and asymmetric transfer hydrogenation in aqueous phaseOn the basis of the above preparation of chiral Ru nano-catalyst,further,by reacting palladium acetate with the polyionic liquid on the surface of the chiral Ru nano-catalyst,the Ru-Pd bimetallic chiral nano-catalyst with a core-shell structure was prepared.Afterwards,the elemental composition and structural morphology of the catalyst were characterized and analyzed.Because of the controllability of the PIL structure,the prepared bimetallic chiral catalyst has a controllable hydrophilicity and hydrophobicity and a controllable critical phase transition temperature(LCST).Above LCST,the polyionic liquid structure on the surface of the catalyst shrinked,and Pd(OAc)₂ on the surface of the catalyst acts to catalyze the Suzuki coupling reaction.When the temperature was lower than LCST,the polyionic liquid on the surface of the catalyst spreads,opening the reaction channel,and the chiral Ru catalyst takes effect to catalyze the asymmetric transfer hydrogenation reaction.The catalyst can efficiently and selectively catalyze the Suzuki coupling and asymmetric transfer hydrogenation reaction in the water phase in one step.In addition,the Ru-Pd chiral nanocatalyst can be recycled,catalyzed 10 times,and the reaction yield and enantioselective were maintained at more than 90%.