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α,β‐Unsaturated Amides as Dipolarophiles: Catalytic Asymmetric exo ‐Selective 1,3‐Dipolar Cycloaddition with Nitrones
Author(s) -
Zhang Ming,
Kumagai Naoya,
Shibasaki Masakatsu
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201702330
Subject(s) - cycloaddition , catalysis , reactivity (psychology) , chemistry , lewis acids and bases , substrate (aquarium) , combinatorial chemistry , organic chemistry , medicine , oceanography , alternative medicine , pathology , geology
1,3‐Dipolar cycloaddition is a commonly exploited method to access 5‐membered chemical entities with a variety of peripheral functionalities and their stereochemical arrangements. Nitrones are isolable 1,3‐dipoles that exhibit sufficient reactivity toward electron‐deficient olefins in the presence of Lewis acids to deliver highly substituted isoxazolidines. Herein we document that α,β‐unsaturated amides, generally regarded as barely reactive in a 1,3‐dipolar reaction manifold, were effectively activated using the designed 7‐azaindoline auxiliary in an In(OTf) 3 /bishydroxamic acid catalytic system. The broad substrate scope and clean removal of the 7‐azaindoline auxiliary from the product highlight the synthetic utility of the present catalysis.