Michael Addition of Chiral Fischer Aminocarbene Complexes to Nitroolefins: Study on the Effect of the Michael Acceptor Structure on Diastereoselectivity

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• 作者：Emanuela Licandro ; Stefano Maiorana ; Laura Capella ; Raffaella Manzotti ; Antonio Papagni ; Barbara Vandoni ; Alberto Albinati ; Shih Hsien Chuang ; and Jih-Ru Hwu
• 刊名：Organometallics
• 出版年：2001
• 出版时间：February 5, 2001
• 年：2001
• 卷：20
• 期：3
• 页码：485 - 496
• 全文大小：328K
• 年卷期：v.20,no.3(February 5, 2001)
• ISSN：1520-6041

文摘

The anions of the pentacarbonyl(chromium) trans-2,6-dimethylmorpholinyl(methyl)carbeneand pentacarbonyl(chromium) trans-3,5-dimethylpiperidinyl(methyl)carbene complexes addedto E- and Z-nitrostyrenes through a diastereoselective Michael-type reaction to giveprecursors of -aryl--butyric acid derivatives. The diastereoselectivity observed with theformer carbene was dependent on the nature of the substituent present in the 4-position ofnitrostyrenes and was higher when it was an electron-withdrawing group. The presence of12-crown-4 ether in the reaction medium increased both reaction times and diastereoselectivity. Theoretical calculations were performed to rationalize the stereochemical outcomesof the reactions and to support the proposed transition state models.