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Benjamin List

Publications and source records attributed to Benjamin List.

25 records · Page 2Linked to original sources
PubMed2004

Combinatorial chemistry and high-throughput screening for the discovery of organocatalysts.

In recent years, interest in organocatalysis, the catalysis with small organic molecules, has been revitalized. Independently, high-throughput-screening and combinatorial chemistry became practical methodologies in the discovery of novel catalytic entities. The logical extension of these methodologies to organocatalysis has led to several interesting results, which are highlighted in this review.

Catalysis↗
PubMed2004

Enamine catalysis is a powerful strategy for the catalytic generation and use of carbanion equivalents.

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 catalysis are summarized in this Account.

Journal Article↗
PubMed2003

Quantum mechanical predictions of the stereoselectivities of proline-catalyzed asymmetric intermolecular aldol reactions.

Quantum mechanical calculations were employed to predict the ratio of four stereoisomeric products expected from two complex reactions involving the aldol reactions of cyclohexanone with benzaldehyde or with isobutyraldehyde catalyzed by (S)-proline. Experimental tests of these predictions provide an assessment of the state-of-the-art in quantum mechanical prediction of products of complex organic reactions in solution.

Alcohols↗
PubMed2003

Kinetic and stereochemical evidence for the involvement of only one proline molecule in the transition states of proline-catalyzed intra- and intermolecular aldol reactions.

Contrary to the widely accepted mechanism of the Hajos-Parrish-Eder-Sauer-Wiechert reaction, we have obtained evidence for the involvement of only one proline molecule in the transition states of both inter- and intramolecular aldol reactions. Our conclusions are based on kinetic measurements and the absence of nonlinear and dilution effects on the asymmetric catalysis, and are supported by B3LYP/6-31G* calculations. Complementary to recent theoretical studies, our results provide the foundation of a unified enamine catalysis mechanism of proline-catalyzed inter- and intramolecular aldol reactions.

Alcohols↗
PubMed2002

Direct catalytic asymmetric alpha-amination of aldehydes.

The first direct catalytic asymmetric alpha-amination of aldehydes is described herein. alpha-Unbranched aldehydes react in this novel proline-catalyzed reaction with dialkyl azodicarboxylates to give alpha-amino aldehydes in excellent yields and enantioselectivities.

Aldehydes↗
PubMed2002

The proline-catalyzed direct asymmetric three-component Mannich reaction: scope, optimization, and application to the highly enantioselective synthesis of 1,2-amino alcohols.

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 discussed. We further present application of our reaction to the highly enantioselective synthesis of 1,2-amino alcohols.

Aldehydes↗