Yujiro Hayashi

The direct, catalytic, asymmetric Michael addition of aldehydes to nitroolefins in the presence of a chiral diphenylprolinol silyl ether organocatalyst is described (see scheme). The desired 1,4-addition products were obtained in nearly optically pure form in good yield with high syn diastereoselectivity. TMS=trimethylsilyl. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z500599_s.pdf or from the author. Please note: The publis

The one-pot synthesis of a target molecule in the same reaction vessel is widely considered to be an efficient approach in synthetic organic chemistry. In this review, the characteristics and limitations of various one-pot syntheses of biologically active molecules are explained, primarily involving organocatalytic methods as key tactics. Besides catalysis, the pot-economy concepts presented herein are also applicable to organometallic and organic reaction methods in general.

Going green: The synthetically very important aldol reaction can proceed in water without a metal catalyst with excellent enantioselectivity. The key to the reaction is a small, synthetic organic catalyst based on trans-hydroxyproline with a siloxy group. Thus, this method is an environmentally friendly process for the synthesis of chiral molecules. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z502488_s.pdf or from the author

Die direkte, katalytische, asymmetrische Michael-Addition von Aldehyden an Nitroolefine in Gegenwart eines chiralen Diphenylprolinolsilylether-Organokatalysators (siehe Schema) liefert hoch syn-diastereoselektiv die gewünschten 1,4-Addukte in nahezu optisch reiner Form und guter Ausbeute. TMS=Trimethylsilyl.

Grüne Chemie: Aldolreaktionen, die in vielen Synthesen eine wichtige Rolle spielen, verlaufen auch in Wasser und ohne Metallkatalysator mit ausgezeichneten Enantioselektivitäten. Entscheidend für diese umweltverträgliche Synthese chiraler Verbindungen ist ein synthetischer Organokatalysator mit trans-Hydroxyprolin-Gerüst und einer Siloxygruppe (siehe Bild; TBDPS=tert-Butyldiphenylsilyl). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_200

What expression best conveys the recent examples of “aqueous” organocatalyzed aldol reactions? It is suggested that a reaction occurs “in water” if the participating reactants are dissolved homogeneously in water (or buffer), or “in the presence of water” if it proceeds in a concentrated organic phase with water present as a second phase that influences the reaction in the former.

Frost formation process was studied by photographic observation, and frost formation types were classified into several groups according to their structure in the temperature range of 0 ∼ −25°C. Frost properties, density and effective thermal conductivity, were clarified in connection with the classified frost formation types, and the prediction of the thermal conductivity was performed by the presented structural model of a frost layer.

A double-crossed reaction: The use of proline as an organocatalyst enables a one-pot, direct, cross-Mannich reaction to be performed between two different aldehydes and 4-methoxyaniline in a highly syn-diastereo- and enantioselective manner (see scheme). Organocatalytic enantioselective reactions1 have received great attention in recent years since the discovery by List and Barbas et al. of aldol reactions using proline as an organocatalyst.2 These reactions are intermolecular variants of the Ha

Why not combine the two? The asymmetric direct aldol reaction of two different aldehydes was catalyzed by a combined proline–surfactant organic catalyst in the presence of water. A stable emulsion was formed in the reaction mixture, and the aldols were obtained with excellent diastereo- and enantioselectivities (see scheme). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2006/z601156_s.pdf or from the author. Please note: The publis

Nitrosobenzene is the oxygen source in the direct catalytic enantioselective α-aminoxylation of ketones catalyzed by L-proline [Eq. (1)]. Versatile α-aminoxylated ketones are obtained in high yield and with excellent enantioselectivities.

Zweifach über Kreuz: Der Einsatz von Prolin als organischem Katalysator ermöglicht eine direkte gekreuzte Eintopf-Mannich-Reaktion zwischen zwei unterschiedlichen Aldehyden und 4-Methoxyanilin, die hochgradig syn-diastereo- und enantioselektiv abläuft.

A choice of three: The tandem Michael/Henry reaction of a nitroalkene and pentane-1,5-dial (generated in situ) proceeded efficiently when diphenylprolinol silyl ether was used as an organocatalyst to afford substituted nitrocyclohexanecarbaldehydes with high diastereo- and enantioselectivity (see scheme; TMS: trimethylsilyl). Isomerization under basic or acidic conditions diastereoselectively converts the product into two stereoisomers, without compromising the enantioselectivity. Supporting inf

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTA Novel Chiral Super-Lewis Acidic Catalyst for Enantioselective SynthesisYujiro Hayashi, Jeffrey J. Rohde, and E. J. CoreyView Author Information Department of Chemistry, Harvard University Cambridge, Massachusetts, 02138 Cite this: J. Am. Chem. Soc. 1996, 118, 23, 5502–5503Publication Date (Web):June 12, 1996Publication History Received8 March 1996Published online12 June 1996Published inissue 1 January 1996https://pubs.acs.org/doi/10.1021/ja9607