Benjamin List

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTProline-Catalyzed Direct Asymmetric Aldol ReactionsBenjamin List, Richard A. Lerner, and Carlos F. BarbasView Author Information The Skaggs Institute for Chemical Biology and the Department of Molecular Biology The Scripps Research Institute 10550 North Torrey Pines Road, La Jolla, California 92037 Cite this: J. Am. Chem. Soc. 2000, 122, 10, 2395–2396Publication Date (Web):February 26, 2000Publication History Received7 December 1999Published onli

The field of asymmetric organocatalysis is rapidly developing and attracts an increasing number of research groups around the world. Here we present a brief overview of this area, guided by a mechanistic classification. Accordingly, organocatalysts are categorized as either Lewis base, Lewis acid, Brønsted base, or Brønsted acid catalysts.

Recently, the use of enantiomerically pure counteranions for the induction of asymmetry in reactions proceeding through cationic intermediates has emerged as an exciting new concept, which has been termed asymmetric counteranion-directed catalysis (ACDC). Despite its success, the concept has not been fully defined and systematically discussed to date. This Review closes this gap by providing a clear definition of ACDC and by examining both clear cases as well as more ambiguous examples to illust

ADVERTISEMENT RETURN TO ISSUEEditorialNEXTIntroduction: OrganocatalysisBenjamin ListView Author Information Max-Planck-Institut für KohlenforschungCite this: Chem. Rev. 2007, 107, 12, 5413–5415Publication Date (Web):December 12, 2007Publication History Published online12 December 2007Published inissue 1 December 2007https://doi.org/10.1021/cr078412eCopyright © 2007 American Chemical SocietyRequest reuse permissions This publication is free to access through this site. Learn MoreArticle Views3938

During the last six years the asymmetric catalysis of carbonyl transformations via iminium ion and enamine intermediates using chiral amines as organocatalysts has grown most remarkably. In this personal account an overview of this area is given. The field can be divided into two sub areas: (a) Iminium catalysis, which is typically used for cycloadditions and conjugate additions to enals and enones and (b) Enamine catalysis, which is commonly used in electrophilic alpha-substitution reactions of

The chemistry of preformed enamines, especially their use as enolate equivalents, has been a well-investigated area of research since the early 1950s. However, enamine catalysis, the catalysis of carbonyl transformations via enamine intermediates by using primary and secondary amines as catalysts, has only been fully appreciated as a powerful strategy for asymmetric synthesis since the beginning of this century. Contributions from this laboratory to the revitalized interest in asymmetric enamine

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTThe Direct Catalytic Asymmetric Three-Component Mannich ReactionBenjamin ListView Author Information Departments of Molecular Biology and Chemistry, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, California 92037 Cite this: J. Am. Chem. Soc. 2000, 122, 38, 9336–9337Publication Date (Web):September 7, 2000Publication History Received1 June 2000Published online7 September 2000Published inissue 1 September 2000https://pubs.

We have developed proline-catalyzed direct asymmetric three-component Mannich reactions of ketones, aldehydes, and amines. Several of the studied reactions provide beta-amino carbonyl compounds (Mannich products) in excellent enantio-, diastereo-, regio-, and chemoselectivities. The scope of each of the three components and the influence of the catalyst structure on the reaction are described. Reaction conditions have been optimized, and the mechanism and source of asymmetric induction are discu

[reaction: see text] Here we describe the proline-catalyzed Michael addition of unmodified ketones to nitro olefins. This novel reaction provides gamma-nitro ketones in modest enantioselectivity yet excellent yields.

This account focuses on novel amine-catalyzed reactions recently discovered in our laboratories. Among the newly developed transformations are efficient proline-catalyzed intermolecular aldol, Mannich, Michael reactions and a novel three-component reaction. 9 Conclusions

[reaction: see text] With this communication we extend the methodology of proline-catalyzed direct asymmetric aldol reactions to include alpha-unsubstituted aldehydes as acceptors. This important aldehyde class gives the corresponding aldols in 22-77% yield and up to 95% ee when the reactions are performed in pure acetone or in ketone/chloroform mixtures. On the basis of these results we have developed a concise new synthesis of (S)-ipsenol.

Small organic molecules are increasingly used as asymmetric catalysts, complementing the enzymes and metal complexes traditionally used to make chiral products.

The mechanism of the proline-catalyzed aldol reaction has stimulated considerable debate, and despite limited experimental data, at least five different mechanisms have been proposed. Complementary to recent theoretical studies we have initiated an experimental program with the goal of clarifying some of the basic mechanistic questions concerning the proline-catalyzed aldol reaction. Here we summarize our discoveries in this area and provide further evidence for the involvement of enamine interm