Asymmetric Synthesis of Spirocyclopentane OxindolesContaining Four Consecutive Stereocenters and Quaternary α-NitroEsters via Organocatalytic Enantioselective Michael–MichaelCascade Reactions

摘要

An enantioselective domino Michael–Michael reaction of nitroolefins and 2-nitro-3-arylacrylates has been established, which provided a series of spirocyclopentane oxindoles with four consecutive stereocenters including quaternary α-nitro esters with good yields (up to 73%) and excellent enantioselectivities (up to 97% ee). The reaction was realized and optimized with the aid of a chiral squaramide-amine catalyst. The structures of 11 products were confirmed by single-crystal X-ray diffraction analysis.