Transition-metals(Palladium And Cobalt)-Catalyzed Asymmetric C(sp~2)-H Bond Functionalization

Chiral compounds exist widely in nature and are widely used in pharmaceuticals,pesticides,optoelectronic materials and other fields.Asymmetric synthesis is an important tool for the synthesis of chiral compounds.In recent years,the transition metal-catalyzed asymmetric C-H bond activation strategy provides a completely new method for the construction of chiral molecules,which has attracted the attention of chemists,and some preliminary progress has been made.However,the development of cheap and easily available chiral ligands and catalysts,and the efficient construction of chiral molecules with novel structures under mild reaction conditions,still face huge challenges.This paper focuses on the construction of axial chiral styrenes and P-central chiral phosphinamides by asymmetric C-H bonds activation.The specific research contents are as follows:1.Palladium catalyzed asymmetric olefination of C(sp~2)-H bonds to construct open-chain axially chiral styrenes.We successfully constructed a class of open-chain axially chiral styrenes through Pd~Ⅱ-catalyzed asymmetric C-H bond alkenylation/dynamic kinetic resolution using L-tert-leucine-derived bulky amino amide as transient chiral auxiliary.In this reaction,a chiral tertiary leucamide and an aldehyde group in the reaction substrate are condensed to form an imine as a transient directing group,and a series of axially chiral compounds can be obtained with high enantioselectivity under mild conditions.Through the structural characterization of the reaction intermediates,we proposed the possible reaction mechanism,and experimentally proved that the activation of C-H bonds is the reaction rate-determining step.Finally,the catalytic asymmetric application of the product is realized via further transformation of the reaction product.2.Synthesis of P-center chiral phosphinamides by Co(Ⅱ)/Salox-catalyzed asymmetric C(sp~2)-H bond activation.We used o-hydroxyaryloxazoline(Salox)as the chiral ligand and cheap and readily available cobalt(II)acetylacetonate as the catalyst to realize the asymmetric C-H bond activation/alkene insertion cyclization reaction to construct P-center chiral phosphinamide compounds.This reaction is different from previously reported cobalt-catalyzed asymmetric catalytic reactions with the aid of chiral Cp~xCo(III),and the commercial cobalt(II)salts was used under mild reaction conditions,It provides a new approach for the synthesis of P-center chiral phosphine oxides,and enriches the asymmetric catalytic system with cheap metal cobalt as the catalyst.