| Stereodivergency in Amine-catalyzed Regioselective [4+2] Cycloadditions of beta-Substituted Cyclic Enones and Polyconjugated Malononitriles. | |
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MedLine Citation:
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PMID: 23151123 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Switchable reaction patterns of beta-substituted cyclic enones have been reported via amine-based dienamine activation. While gama-regioselective vinylogous Michael addition was observed with alkylidenemalononitriles, a completely different [4+2] cycloaddition was obtained with allylidene- or alkynylidenemanolonitrile substrates, affording densely substituted bicyclo[2.2.2]octanes or analogous architectures with moderate to excellent diastereo- and enantioselectivity by the catalysis of primary amines from natural quinidine or quinine. Importantly, high diastereodivergency was achieved through unusual hydrogen bonding interactions of multifunctional primary amino catalytic systems. Endo-cycloadducts were efficiently produced using a supramolecular combination of 9-amino-9-deoxyepiquinidine and salicylic acid, while exo-variants were obtained using 6'-OH-9-amino-9-deoxyepiquinidine. Moreover, we have successfully isolated the Michael addition intermediates in some cases, indicating that the above [4+2] reaction via dienamine catalysis proceeds in a stepwise Michael/Michael cascade, rather than in a concerted Diels-Alder cycloaddition pathway. |
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Authors:
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Xin Feng; Zhi Zhou; Rong Zhou; Qing-Qing Zhou; Lin Dong; Ying-Chun Chen |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-11-15 |
Journal Detail:
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Title: Journal of the American Chemical Society Volume: - ISSN: 1520-5126 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2012 Nov |
Date Detail:
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Created Date: 2012-11-15 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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