Preparation Of Polymer Supported Cinchona Alkaloids And Their Catalytic Performance For Asymmetric Michael Reaction

Polymer-supported chiral catalysts as heterogeneous catalysts have merits such as easy separation and good recyclability and can be used to overcome the drawbacks such as high dosage and poor recyclability of homogeneous catalysts, well in accordance with the requriemens for green chemistry and sustainable development. Thus 10 novel polymer-supported chiral catalysts were synthesized via various synthetic routes, and the catalytic performance of as-synthesized products for asymmetric Michael reaction was evaluated. The main contents and research results of the present thesis are as follows:1. Six kinds of polymer-supported cinchona alkaloid (quinine) catalysts were synthesized by way of the grafting reaction between natural cinchona alkaloid and synthetic macromolecules. As-synthesized products were used to catalyze the asymmetric Michael addition reaction of 1,3-dicarbonyl compounds and N-benzyl maleimide. The effects of substrate, solvent, and catalyst dosage on the catalytic performance were investigated, and the recyclability of the catalysts was examined. It has been found that 6 kinds of as-synthesized polymer-supported cinchona alkaloid catalysts are all able to catalyze the asymmetric Michael addition reaction of 1,3-dicarbonyl compounds and N-benzylmaleimide, and catalyst V possesses the best catalytic performance. Namely, catalyst V has relatively higher stereoselectivity and activity in suitable solvents (the yield is as much as 83%, and ee value is as much as 86%), and it is dominated by mild reaction condition, good recovery behavior and good recyclability (it can be recycled for at least 6 times).2. Chitosan, a natural macromolecule containing abundant amino group and hydroxyl group, was used as a carrier to synthesize two kinds of chitosan-supported cinchona alkaloid complexes via a simple route. The catalytic performance of resultant chitosan-supported cinchona alkaloid complexes as heterogeneous catalysts for the asymmetric Michael addition reaction of 1,3-dicarbonyl compounds and N-benzyl maleimide was evaluated. It has been found that as-synthesized chitosan-supported cinchona alkaloids as organocatalysts for asymmetric Michael addition reaction possess good enantioselectivity (the ee value is equal to 94%, and dr value is equal to 85 : 15) and can well catalyze the formation of functioanlzed products containing densely-packed adjacent tertiary and quaternary carbon atom stereocenters in high yields and good recyclability (up to 5 runs). Thanks to simple synthetic procedures plus good environmetal acceptability and recyclability, as-synthesized chitosan-supported cinchona alkaloids show promising advantages as organocatalysts supported by natural macromolecules.3. mercaptomethyl-polystyrene resin, chitosan and quinine were used as raw materials to synthesize mercaptomethyl-polystyrene resin-supported cupreine catalyst and chitosan-supported cupreine catalyst. As-synthesized products were used to catalyze the asymmetric Michael addition reaction of nitro olefin and dimethyl malonate; and the effects of solvent, catalyst dosage, temperature, and substrate on the catalytic performance of mercaptomethyl-polystyrene resin-supported cupreine catalyst were investigated. It has been found that the two kinds of polymer-supported catalysts can both effectively catalyze the asymmetric Michael addition reaction of nitro olefin and dimethyl malonate. Particularly, mercaptomethyl-polystyrene resin-supported cupreine catalyst has a high catalytic activity and good enantioselectivity in tetrahydrofuran, with the yield being over 80% and ee value being 88%, while it can be easily recycled and possess good reusability.