Asymmetric Pd(0)/Rh(?) Dual Catalysis Synthesis Of Chiral ?-quaternary ?-keto-esters

The chemical structures containing chiral quaternary carbon centers are widely found in natural products,drug molecules and organic active molecules.This special units are rich in structural diversity,and can enhance the conformational constraint ability of the compounds.It has an important influence on the biological activity of natural products.Due to the large steric effects of chiral quaternary carbon centers,it is difficult to construct chiral quaternary carbon centers through organic synthesis.It is still a research hotspot that the simple and efficient synthesis of multifunctional chiral quaternary carbon centers.In many synthetic methods of chiral quaternary carbon centers,gem-Difunctionalization is a good choice for the construction chiral quaternary carbon centers.In asymmetric synthesis,asymmetric allyl alkylation is a powerful tool for constructing chiral centers.Using dual metal catalytic strategy to introduce an asymmetric allyl alkylation reaction during the gem-Difunctionalization.This method can not only strengthen the construction of chiral quaternary carbon centers,but also introduce polyfunctional allyl groups into the molecule.In order to achieve the purpose of simple and efficient construction of multifunctional chiral quaternary carbon center.In this paper,the Pd(0)/Rh(?)dual catalyst system was used to study the synthesis of multifunctional chiral quaternary carbon center compounds.Through the asymmetric allyl alkylation reaction of ?-diazocarbonyl compounds,the construction of chiral quaternary carbon center was realized.It mainly includes the following two parts:1.Used Pd(0)/Rh(?)dual catalyst system asymmetric catalyed synthesis of ?quaternary carbon-?-ketoester compounds through allyl alkylation of gem-Difunctionalization.Two separate C-C ?-bonds at the carbenic center were formed in a straightforward manner by the rhodium carbene induced Semipinacol rearrangement/allyl alkylation cascade reactions.This transformation represents a highly efficient method for the one-pot synthesis of ?quaternary ?-keto-esters under mild conditions.During the asymmetric allyl alkylation process,the chiral phosphorus ligand complex with the palladium catalyst was used to control the enantioselectivity of the reaction,and the 53%enantioselectivity was obtained.2.Used Pd(0)/Rh(?)dual catalyst system asymmetric catalyed synthesis of dihydrofuran-3-ones compounds.Exploring the influence of conditions on the reaction to improved the enantioselectivity of the reactions(such as catalysts,chiral ligands,substrate structure,temperature and others).Through the used of Trost chiral ligands and modified allyl reagents,67%enantioselectivity were obtained in ynthesis of dihydrofuran-3-ones compounds.