Cooperative Catalysis with Coupled Chiral Induction in 1,3‐Dipolar Cycloadditions of Azomethine Ylides

Cooperative Catalysis with Coupled Chiral Induction in 1,3‐Dipolar Cycloadditions of Azomethine... 1,3‐Dipolar cycloadditions (1,3‐DC) between imino esters (as precursors of N‐metallated azomethine ylides) and π‐deficient alkenes are promoted by cooperative asymmetric Lewis acid/Brønsted base catalysis. The components of these catalytic pairs are silver salts derived from enantiopure commercially available BINOL‐based phosphoric acids and Cinchona alkaloids. Chiral phosphoric silver(I) salts promote HOMO raising of in situ formed 1,3‐dipoles, whereas protonated cinchona alkaloids generate a LUMO lowering for the dipolarophiles resulting in a global acceleration of the 1,3‐DC. The best results were obtained with BINOL‐derived silver phosphate and hydrocinchonine. Matching between both cooperative metallo‐ and organocatalyst results in an enhanced enantiomeric excess, superior to that reached by both separate components. NOESY experiments and DFT calculations are compatible with a non‐covalent interaction (hydrogen bond) between both catalysts, which results in close contacts and mutually coupled chiral environments. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Chemistry - A European Journal Wiley

Cooperative Catalysis with Coupled Chiral Induction in 1,3‐Dipolar Cycloadditions of Azomethine Ylides

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Publisher
Wiley Subscription Services, Inc., A Wiley Company
Copyright
© 2018 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim
ISSN
0947-6539
eISSN
1521-3765
D.O.I.
10.1002/chem.201801433
Publisher site
See Article on Publisher Site

Abstract

1,3‐Dipolar cycloadditions (1,3‐DC) between imino esters (as precursors of N‐metallated azomethine ylides) and π‐deficient alkenes are promoted by cooperative asymmetric Lewis acid/Brønsted base catalysis. The components of these catalytic pairs are silver salts derived from enantiopure commercially available BINOL‐based phosphoric acids and Cinchona alkaloids. Chiral phosphoric silver(I) salts promote HOMO raising of in situ formed 1,3‐dipoles, whereas protonated cinchona alkaloids generate a LUMO lowering for the dipolarophiles resulting in a global acceleration of the 1,3‐DC. The best results were obtained with BINOL‐derived silver phosphate and hydrocinchonine. Matching between both cooperative metallo‐ and organocatalyst results in an enhanced enantiomeric excess, superior to that reached by both separate components. NOESY experiments and DFT calculations are compatible with a non‐covalent interaction (hydrogen bond) between both catalysts, which results in close contacts and mutually coupled chiral environments.

Journal

Chemistry - A European JournalWiley

Published: Jan 7, 2018

Keywords: ; ; ; ;

References

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