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Stereodivergency in Amine-catalyzed Regioselective [4+2] Cycloadditions of beta-Substituted Cyclic Enones and Polyconjugated Malononitriles.
MedLine Citation:
PMID:  23151123     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
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.
Authors:
Xin Feng; Zhi Zhou; Rong Zhou; Qing-Qing Zhou; Lin Dong; Ying-Chun Chen
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-11-15
Journal Detail:
Title:  Journal of the American Chemical Society     Volume:  -     ISSN:  1520-5126     ISO Abbreviation:  J. Am. Chem. Soc.     Publication Date:  2012 Nov 
Date Detail:
Created Date:  2012-11-15     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  7503056     Medline TA:  J Am Chem Soc     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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