Toward the Development of a General Chiral Auxiliary. 3. Design and Evaluation of a Novel Chiral Bicyclic Lactam for Asymmetric Aldol Condensations: Evidence for the Importance of Dipole Alignment in the Transition State

1995 ◽  
Vol 117 (49) ◽  
pp. 12368-12369 ◽  
Author(s):  
Robert K. Boeckman ◽  
Brian T. Connell
Keyword(s):  
Transition State ◽  
Chiral Auxiliary ◽  
Asymmetric Aldol ◽  
Dipole Alignment

Asymmetric aldol reactions employing a cyclic sulfamide chiral auxiliary

1992 ◽  
Vol 33 (44) ◽  
pp. 6661-6664 ◽  
Author(s):  
Kyo Han Ahn ◽  
Dong Jin Yoo ◽  
Jeong Sook Kim
Keyword(s):  
Chiral Auxiliary ◽  
Aldol Reactions ◽  
Asymmetric Aldol

New Mechanistic Approach in the Enamine-Based Asymmetric Organocatalysis

2021 ◽  
Author(s):  
András A. Gurka
Keyword(s):  
Water Molecule ◽  
Transition State ◽  
Aqueous Media ◽  
Initial Step ◽  
Aldol Reactions ◽  
Asymmetric Aldol ◽  
Mechanistic Approach ◽  
Asymmetric Organocatalysis ◽  
Organocatalytic Reactions ◽  
Proline Derivatives

Abstract During the course of my research in asymmetric organocatalysis the inversion of enantioselectivity was observed in the asymmetric aldol reactions of acetone with different aldehydes catalyzed by amphiphilic proline derivatives in aqueous media varying only achiral components. It was not possible to explain the explored dual stereocontrol with the existing models, therefore I proposed a new mechanism for asymmetric aldol reactions catalyzed by l-amino acid derivatives in aqueous media and explained the explored phenomenon of inversion of enantioselectivity with different structures of micelle-stabilized transition state described as a metal-free version of the Zimmermann-Traxler model with explicit participation of a water molecule. Contrary to the existing models, according to the proposed mechanism the formation of new bonds proceeds directly in the transition state stabilized by a water molecule without the additional step of product iminium ion hydrolysis. The proposed mechanism has universal character, it is consistent with experimental results and general theoretical conceptions and it is applicable to all enamine-based asymmetric organocatalytic reactions carried out not only in aqueous, but in organic media as well, because the initial step of catalytic cycle, which involves the formation of an enamine from the carbonyl compound and proline (derivative), liberates one water molecule.

ChemInform Abstract: Asymmetric Aldol Reactions Using Chiral CF3-Oxazolidines (Fox) as Chiral Auxiliary.

ChemInform ◽  
2010 ◽  
Vol 41 (18) ◽  
Author(s):  
Arnaud Tessier ◽  
Julien Pytkowicz ◽  
Thierry Brigaud
Keyword(s):  
Chiral Auxiliary ◽  
Aldol Reactions ◽  
Asymmetric Aldol

Asymmetric aldol and alkylation reactions mediated by the “quat” chiral auxiliary (R)-(−)-5-methyl-3,3-dimethyl-2-pyrrolidinone

1994 ◽  
Vol 35 (15) ◽  
pp. 2373-2376 ◽  
Author(s):  
Stephen G. Davies ◽  
Gilles J.-M. Doisneau ◽  
Jeremy C. Prodger ◽  
Hitesh J. Sanganee
Keyword(s):  
Chiral Auxiliary ◽  
Asymmetric Aldol ◽  
Alkylation Reactions
Sign in / Sign up

Export Citation Format

Share Document