Transition Metal And Chiral Lewis Base Cooperatively Catalyzed Asymmetric Reactions

In recent years,organo/metal combined catalysis has experienced great progress and become an important method for the synthesis of structurally diverse chiral compounds.The combination of metals and organocatalysts can take advantages of both catalysts and allows the simultaneous or sequential occurrence of multiply bondbreaking and forming events enantioselectively that are toughly accessed by the individual catalyst,delivering diverse ranges of chiral functional molecules.The theme of this thesis is mainly focusing on the transition metal and chiral Lewis base cooperatively catalyzed asymmetric reactions.Highly enantioselective[4+2]cyclization of azadienes with in situ generated ketenes has been developed through sequential visible-light photoactivation/isothiourea catalysis,which offers a novel approach to create all-carbon quaternary stereocenters through disubstituted Cl-ammonium enolates.The visible-light-induced sustained release of reactive ketene species through Wolff rearrangement of α-diazoketones is crucial for achieving high levels of chemical efficiency and stereoinduction.Based on the relay catalysis of rhodium and chiral isothiourea,we have established an asymmetric oxidative annulation of alkynes and imines.In the presence of rhodium catalyst and 4-picoline-N-oxide,alkyne compounds are transformed into ketene intermediates through transfer oxidation,which are subsequently captured by chiral isothioureas to generated Cl-ammonium enolates and then undergo asymmetric cyclization with unsaturated imines and perfluorobutyl-substituted ketones to construct a series of chiral dihydropyridones and β-lactone derivatives with high yield and stereoselectivity.The feasibility of cooperative catalysis between chiral N-heterocyclic carbenes and nickel in asymmetric reactions has been demonstrated convincingly.The high efficiency of this catalytic system enables the asymmetric allylic alkylation of isatinderived enals with allylic carbonates and[3+3]annulation with racemic vinyl epoxides to provide straightforward access to highly enantioenriched 3,3’-disubstituted oxindoles.Nickel complexes and chiral N-heterocyclic carbenes have good compatibility and can independently activate the reaction component.