NHC-copper-catalyzed Asymmetric Conjugate Silylation To Access Chiral ?-Aminosilanes

Silicon and carbon are in the same main group,so they have similar valence electron structure and bonding properties.They are often used as carbon isoelectronics and their unique structure and physicochemical properties make organosilicon compounds widely used in materials and synthetic chemistry.On the other hand,silicon atoms have a larger atomic radius than carbon,stronger positive charge,better fat solubility and lower toxicity.Organosilane compounds have found widespread applications in synthetic and medicinal chemistry.Among these,chiral ?-aminosilanes have gained increasing attention because they have shown significant bioactivities.Accordingly,many methods have been developed in the synthesis of these structures.However,only a few methods have been reported for their asymmetric synthesis.Tranditonal methods rely on diastereoselective synthesis with involvement of organolithium reagents,which usually suffered from limitations such as narrow functional group tolorence and harsh reaction conditions.Examples inlcude reverse aza-Brook rearrangement and the addition of silyllithium reagents to the chiral aldimines,.On the other hand,elegant copper-catalyzed asymmetric transformations provide mild and straightfoward approaches to access these structures with wide functional group compatibility.However,there are still some limitations.For examples,reactions of aldimines or silyl ketimines are restricted to aryl substrates;hydroamination of vinylsilanes requires expensive silanes as hydride source and instable aminating reagents.In addition,catalytic methods to synthesizing chiral ?-aminosilanes with functional groups such as ester,cyanide,amide and halogens remain virtually unexporlored,which hamper further application of these methods.Thus,it is still appealing to develop effiecient methods to prepare ?-aminosilanes with multiple functionalities.To this end,we herein develop the NHC-copper catalyzed asymmetric conjugate silylation reactions of ?-amido-acrylonitrles and ?-amido-acrylates for the first time in the presence of catalytic amount of chiral N-heterocyclic carbene(NHC)/Copper(I)complex.A varitey of functionalized chiral ?-Aminosilanes were obtained in good yields with high enantioselectivities.