The Study Of Chiral Bisoxamides/Rare-Earth Metal Complexes Catalyzed Inverse-Electron-Demand Asymmetric Oxa-Diels-Alder Reaction

In recent several decades,rare-earth metal complexes-catalyzed asymmetric reactions have made great advances.In this thesis,various types of inverse-electrondemand asymmetric oxa-Diels-Alder reactions were fulfilled by the use of β,γunsaturated-α-ketoesters as enophiles and cyclopentadiene,2,3-dihydrofuran.phenyl(vinyl)sulfane and cyclic enamine as dienophiles,which were catalyzed by chiral bis-oxalamide/rare-earth metal complexes.The asymmetric oxa-Diels-Alder reactions developed were used to construct a range of optically active dihydropyran or ring-fused pyran derivatives in high yields with high stereoselectivity.In the first part,the inverse-electron-demand asymmetric Diels-Alder reaction ofβ,γ-unsaturated-α-ketoesters with cyclopentadiene was achieved using a chiral bisoxalamide/scandium(Ⅲ)complex as a catalyst.The corresponding asymmetric oxaDiels-Alder reaction provided a series of adducts in up to 75%yield with>20:1 dr and 97%ee.The coordination mode of chiral bis-oxalamide with Sc(Ⅲ)was demonstrated by the X-ray crystallographic structure,and two nitrogens and two oxygens of CBOA ligand coordinate to Sc(Ⅲ)in a tetradentate manner to form fivemembered chelating rings.The nonlinear effect(NLE)for the corresponding model reaction was investigated,and a positive nonlinear effect was observed.The results indicate that the polymeric L1-Sc(OTf)3 complex may be catalytic species in this reaction system.In the second part,we have further examined the application of chiral bisoxalamide/rare-earth metal complexes in inverse-electron-demand asymmetric heteroDiels-Alder reactions of β,γ-unsaturated-α-ketoesters with 2,3-dihydrofuran,3,4dihydro-2H-pyran,phenyl(vinyl)sulfane or cyclic enamine.The asymmetric oxaDiels-Alder reactions of β,γ-unsaturated-α-ketoesters with 2,3-dihydrofuran or 3,4dihydro-2H-pyran were catalyzed by chiral bis-oxalamide/scandium(Ⅲ)complexes,and the target products were obtained in up to 99%yield with 93%ee and>20:1 dr.When chiral bis-oxalamide/yttrium(Ⅲ)complexes were employed as the catalysts,theβ,γ-unsaturated-α-ketoesters reacted with phenyl(vinyl)sulfane to afford the desired products in 99%yield with 91%ee and>20:1 dr.Finally,we briefly investigated the oxa-Diels-Alder reaction of β,γ-unsaturated-α-ketoesters with cyclic enamine catalyzed by a chiral bis-oxalamide/scandium(Ⅲ)complex,and the target product was obtained in up to 55%yield with 85%ee and>20:1 dr.