Construction Of Chiral Bifunctional Phase Transfer Catalyst And Its Catalytic Asymmetric Amination

Asymmetric catalysis is an important way to obtain chiral molecules and materials.Since 1970s,with the advent and development of phase transfer catalyst technology,chiral phase transfer catalysis has been rapidly developed into a popular direction in organic chemistry.In recent years,a variety of new chiral phase transfer catalysts have emerged,new types of catalyst systems have also been established,more and more chiral phase transfer catalysts can be used for asymmetric catalytic reaction under mild conditions,including Alkylation,Michael addition and Epoxidation,Darzen reaction,and Amino acid synthesis,Mannich reaction,etc.With the development of phase transfer catalysis,organic catalysis has gradually become the third pillar of modern asymmetric catalysis beyond biocatalysis and metal catalysis,because it does not involve toxic metals or expensive biocatalyst for selective conversion.Study of phase transfer catalysis is of major significance,at the same time,phase transfer catalysis is less used in amination.Therefore,based on the advantages of phase transfer catalysis,we designed and synthesized new chiral bifunctional phase transfer catalysts,and initially explored their catalytic performances in asymmetric amination reactions.At the same time,a novel catalyst-free amination was discovered by using water as solvent or solely by simple grinding means.This thesis includes the following three aspects:1.Four kinds of novel chiral bifunctional phase transfer catalysts?including 11 catalysts? are synthesized from tartaric acid,3-amino pyrrolidine,amino acids and ferrocene by 3⁵ steps classical reactions,respectively,containing hydroxyl,urea,thiourea and amide group to form hydrogen bonds with substrates for enhancement of enantioselectivities.All prepared catalysts have been characterized by their ¹H NMR,¹³C NMR and HRMS.2.The amination of trans-?-nitrostyrene and amination reagent BocNHOBn catalyzed by the synthesized chiral bifunctional phase transfer catalysts are initially investigated. The influences of the catalysts structures,reaction solvents,additives,temperature and other factors on the reaction were studied in detail,so as to screen out the best catalysts and the optimal catalytic system.The catalytic system for the amination of all substituted trans-?-nitrostyrenes and amination reagents,BocNHOBn,was investigated with the optimal catalyst?amino acid derivatives-squaramides skeleton?, under the amount of 0.5¹ mol%catalyst,with water:toluene=10:1?volume ratio?as solvent,8h at 0?or 4h at room temperature,the corresponding amination products were obtained in high yields?up to 96%?and enantioselectivities?up to 93%ee?.The dominant configuration of the product is R configuration.3.From the above research processes,we found that the novel amination reaction of trans-?-nitrostyrenes and another amination reagent BnONH₂ can be achieved in water system or by grinding process without adding any catalyst,and the amination products can be obtained with quantitative chemical yields.This amination is simple, rapid,quantitative,gram-level scale operation,with all the advantages of green organic synthesis.The products can be further converted into diamines for the efficient synthesis of various chiral N-containing compounds.The experimental results demonstrated that these novel chiral bifunctional phase transfer catalysts have good catalytic effect in the amination of trans-?-nitrostyrenes and BocNHOBn,with high yields and excellent enantioselectivities.