Asymmetric direct vinylogous carbon-carbon bond formation catalyzed by bifunctional organocatalysts |
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Authors: | Lin Jiang Tian-Yu Liu Ying-Chun Chen |
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Institution: | a Key Laboratory of Drug-Targeting of Education Ministry and Department of Medicinal Chemistry, West China School of Pharmacy, Sichuan University, Chengdu 610041, China b Department of Endocrinology, Xinqiao Hospital, Third Military Medical University, Chongqing 400037, China |
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Abstract: | The bifunctional chiral thiourea-tertiary amine organocatalysts have been applied to a direct asymmetric vinylogous Michael addition of α,α-dicyanoolefins to nitroolefins with 2-10 mol % catalyst loadings. The electronic properties of the thiourea-based catalysts have significant influences on this reaction. Moderate to excellent enantioselectivities (57-95% ee) have been achieved with low to good isolated yields through fine tuning the structures of the bifunctional organocatalysts. Much better ees were obtained for some α,α-dicyanoolefinic substrates compared with that catalyzed by modified cinchona alkaloids. |
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