Asymmetric organocatalytic conjugate addition of dialkyl phosphites to N-unprotected isatylidene malononitriles: access to 3-phospho-2-oxindoles with chiral quaternary stereocenters |
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Authors: | Zhao-Min Liu Nai-Kai LiXiao-Fei Huang Bing WuNing Li Chun-Yuen KwokYong Wang Xing-Wang Wang |
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Affiliation: | Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, PR China |
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Abstract: | The enantioselective Michael addition of dialkyl phosphites to N-unprotected isatylidene malononitriles has been established for the first time by using a simple bifunctional tertiary amine–thiourea catalyst. The corresponding adducts, 3-phospho-2-oxindoles, containing a chiral quaternary carbon center at the 3-position of the oxindole, were obtained in good to excellent yields (up to 98%) with moderate to excellent enantioselectivities (up to 95% ee). In addition, optically active 3,3′-disubstituted oxindoles bearing carboxylate and phosphonate groups were facilely obtained by the oxidative degradation of the Michael adducts. |
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Keywords: | Asymmetric organocatalysis Tertiary amine&ndash thiourea Phospha-Michael Dialkyl phosphites 3-Phospho-2-oxindoles |
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