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Asymmetric Synthesis of Spirocyclopentane Oxindoles Containing Four Consecutive Stereocenters and Quaternary α‑Nitro Esters via Organocatalytic Enantioselective Michael–Michael Cascade Reactions

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journal contribution
posted on 09.01.2019, 09:31 by Prakash D. Chaudhari, Bor-Cherng Hong, Chao-Lin Wen, Gene-Hsiang Lee
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.