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Molecules 2015, 20(8), 13642-13658; doi:10.3390/molecules200813642

Diastereodivergent and Enantioselective [4+2] Annulations of γ-Butenolides with Cyclic 1-Azadienes

1
,
1,* and 1,2,*
1
College of Pharmacy, Third Military Medical University, Chongqing 400038, China
2
Key Laboratory of Drug-Targeting and Drug Delivery System of the Ministry of Education, West China School of Pharmacy, Sichuan University, Chengdu 610041, China
*
Authors to whom correspondence should be addressed.
Academic Editor: Choon-Hong Tan
Received: 9 June 2015 / Revised: 12 July 2015 / Accepted: 13 July 2015 / Published: 27 July 2015
(This article belongs to the Special Issue Brønsted Base Catalysis in Organic Synthesis)
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Abstract

An asymmetric annulation reaction of γ-butenolides and cyclic 1-azadienes containing a 1,2-benzoisothiazole-1,1-dioxide motif has been studied, proceeding in a tandem Michael addition-aza-Michael addition sequence. Endo-type cycloadducts bearing fused tetracyclic skeletons were isolated in fair yields and with high enantioselectivity (up to >99% ee) under the catalysis of modified cinchona alkaloid (DHQD)2PHAL. Besides, exo-type diastereomers could be produced using β-isocupreidine (β-ICD) as the catalyst, though with moderate enantioselectivity. View Full-Text
Keywords: asymmetric organocatalysis; Brønsted base; cinchona alkaloids; butenolides; 1-azadienes; diastereodivergence asymmetric organocatalysis; Brønsted base; cinchona alkaloids; butenolides; 1-azadienes; diastereodivergence
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Li, C.; Jiang, K.; Chen, Y.-C. Diastereodivergent and Enantioselective [4+2] Annulations of γ-Butenolides with Cyclic 1-Azadienes. Molecules 2015, 20, 13642-13658.

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