A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chir...A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chiral nickel carbenoid intermediate and the following enantioselective cycloaddition reaction. The desired dihydrofuran O,O-acetal derivatives were obtained in good yields(up to 90%) with high enantioselectivity(up to 99% ee) under mild reaction conditions within short reaction time. On the basis of the determination of the catalyst structure, a possible transition state mode was proposed.展开更多
The construction of polycyclic scaffolds is a sophisticated area of chemical synthesis,however,the direct synthesis of readily accessible chiral 4H-pyran-containing polycyclic compounds remains challenging,likely due ...The construction of polycyclic scaffolds is a sophisticated area of chemical synthesis,however,the direct synthesis of readily accessible chiral 4H-pyran-containing polycyclic compounds remains challenging,likely due to the lack of rational substrate design,appropriate reaction selection,and highly effective catalytic systems.Herein,we present the design and development of a novel organocatalytic cascade reaction for constructing structurally complex chiral polycyclic 4H-pyran scaffolds,featuring adjacent quaternary and tertiary stereocenters,in high yields and excellent stereoselectivities,promoted by a bifunctional phosphonium salt catalyst(up to 95% yield and 98%ee,all>20:1 dr).Additionally,experimental studies and density functional theory(DFT)calculations revealed an intricate cascade process involving Michael addition,nucleophilic addition,isomerization,oxa-nucleophilic attack,and protonation sequences.Hydrogen bonding and CH-πinteractions collaboratively enhance the high enantioselectivities in this innovative cascade protocol.展开更多
N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high...N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high nucleophilicity.Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis,chiral NHOmediated highly enantioselective organic transformations were still elusive.Herein,we developed a new type of chiral aminederived C_(2)-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetricα-functionalization ofβ-ketoesters.With as low as 0.1 mol%catalyst loading,the desired amination and trifluoromethylthiolation products were afforded in good yields with high enantioselectivities(up to 99%yield and 99%ee).Experimental studies and theoretical calculation disclosed that hydrogen-bonding interaction upon protonation and other weak interaction between substrate and catalyst were crucial for the enantiocontrol.展开更多
基金the National Natural Science Foundation of China(No. 22188101)Sichuan Science and Technology Program (No.2021YJ0561)Sichuan University (No. 2020SCUNL204)for financial support。
文摘A highly efficient asymmetric(3 + 2) cycloaddition of α-diazo pyrazoleamides with silyl enol ethers was realized by employing a chiral N,N’-dioxide-Ni(II) complex catalyst. The process includes the formation of chiral nickel carbenoid intermediate and the following enantioselective cycloaddition reaction. The desired dihydrofuran O,O-acetal derivatives were obtained in good yields(up to 90%) with high enantioselectivity(up to 99% ee) under mild reaction conditions within short reaction time. On the basis of the determination of the catalyst structure, a possible transition state mode was proposed.
基金supported by the National Natural Science Foundation of China(22222109,21921002,22101189,22371190)the National Key R&D Program of China(2018YFA0903500)+5 种基金the Beijing National Laboratory for Molecular Sciences(BNLMS202101)the Sichuan Science Foundation for Distinguished Young Scholars(2023NSFSC1921)the Sichuan Provincial Natural Science Foundation(2022NSFSC1181,24NSFSC6590)the Fundamental Research Funds from Sichuan University(2020SCUNL108)the Fundamental Research Funds for the Central Universitiesthe College of Chemistry and the Analytical&Testing Center of Sichuan University for the support。
文摘The construction of polycyclic scaffolds is a sophisticated area of chemical synthesis,however,the direct synthesis of readily accessible chiral 4H-pyran-containing polycyclic compounds remains challenging,likely due to the lack of rational substrate design,appropriate reaction selection,and highly effective catalytic systems.Herein,we present the design and development of a novel organocatalytic cascade reaction for constructing structurally complex chiral polycyclic 4H-pyran scaffolds,featuring adjacent quaternary and tertiary stereocenters,in high yields and excellent stereoselectivities,promoted by a bifunctional phosphonium salt catalyst(up to 95% yield and 98%ee,all>20:1 dr).Additionally,experimental studies and density functional theory(DFT)calculations revealed an intricate cascade process involving Michael addition,nucleophilic addition,isomerization,oxa-nucleophilic attack,and protonation sequences.Hydrogen bonding and CH-πinteractions collaboratively enhance the high enantioselectivities in this innovative cascade protocol.
基金supported by the National Natural Science Foundation of China(92056107,22271199,21801175)the Sichuan University(2020SCUNL204)。
文摘N-heterocyclic olefins(NHOs)possess an electron-rich and highly polarized C=C double bond due to the donating property of nitrogen atoms.This feature imparts exocyclic carbon atom of NHOs with strong basicity and high nucleophilicity.Although NHOs have been emerging as a new type of organocatalyst and ligand for metal complexes in organic synthesis,chiral NHOmediated highly enantioselective organic transformations were still elusive.Herein,we developed a new type of chiral aminederived C_(2)-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetricα-functionalization ofβ-ketoesters.With as low as 0.1 mol%catalyst loading,the desired amination and trifluoromethylthiolation products were afforded in good yields with high enantioselectivities(up to 99%yield and 99%ee).Experimental studies and theoretical calculation disclosed that hydrogen-bonding interaction upon protonation and other weak interaction between substrate and catalyst were crucial for the enantiocontrol.
