New chiral N-heterocyclic olefin bifunctional organocatalysis inα-functionalization of β-ketoesters

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 C2-symmetric NHOs and employed them as efficient chiral bifunctional organocatalysts for asymmetric α-functionalization of β-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.