Study On The Synthesis Of Novel Chiral Amine-squaramide Bifunctional Catalyst And Catalytic Behaviors For The Asymmetric Michael Reaction

Organocatalysis has shown its stupendous potentiality because of its advantages of mild reaction conditions,economy and low toxicity,while bifunctional catalysts displayed their excellent stereoselectivities in the past decade.Isostiviol,a kind of cheap and readily available natural product,with a hydrophobic rigid skeleton and a stable chiral microenvironment,makes catalysts based on it possess capacity to catalyze asymmetric reactions with high selectivity.In this dissertation,based on the idea of “organic bifunctional catalysts”,eight novel chiral amine-squaramide type bifunctional organocatalysts with isostiviol as the chiral skeleton were designed and synthesized,characterized and used for the stereoselective catalysis of asymmetric Michael reactions.???The catalyzed asymmetric Michael addition reaction of 1,3-cyclohexanedione with ?,?-unsaturated-?-ketoester was investigated with the synthesized amine- squaramide type compounds as catalysts.Cat-8a was selected to show its good catalytic properties,excellent yields(up to 97%)and enantioselectivities(up to 99% ee),that were achieved with 1 mmol% of the catalyst under the optimized conditions.The proposed transition state was provided.???In the asymmetric Michael addition reaction of 1,3-cyclohexanedione and(E)-?-bromo-?-nitrostyrene,Cat.11 a exhibits good catalytic performance after a screening on the dosage of catalyst,solvent,auxiliary base,temperature etc.,a result of good yields(up to 99%)and good enantioselectivities(up to 96% ee)was obtained.A possible mechanism was proposed for the chiral bifunctional organocatalysts catalyzed Michael addition reaction followed by the nucleophilic substitution/cyclyzation reaction.The catalytic behaviors of the novel compound were considered as the double hydrogen bonding,which induced the substrates in the trasition state to their suitable space orientation.It was also found that the silver carbonate as auxiliary alkaline reagent can obviously promote the catalyzed reactions.???...