<i>C</i><sub>3</sub>‐Symmetric Proline‐Functionalized Organocatalysts: Enantioselective Michael Addition Reactions

Moorthy, Jarugu Narasimha; Saha, Satyajit

doi:10.1002/ejoc.201000569

Cited by 42 publications

(23 citation statements)

References 65 publications

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“…However, the use of (S)-proline-2,4,6-trinitroanilide (20 mol%) as catalyst for the reaction of acetone and aromatic aldehydes gave only good results with aldehydes bearing electron-withdrawing groups (48-90% yield and 78-89% ee) [164]. Nevertheless, prolinamide 119 catalyzed the reaction of several ketones with aromatic aldehydes leading to the expected aldols with up to 95% ee in the presence of TFA as cocatalyst ((4), Scheme 3.28) [165]. The simple amide (120) has been used in the reaction between α-chloroacetone (X = Cl in 58) and aromatic aldehydes affording mainly the compound anti-59 with a minor amount of iso-60 (X = Cl, (5)) [166].…”

Section: Aldehydes As Electrophilesmentioning

confidence: 99%

Organocatalyzed Aldol Reactions

Guillena¹

2013

Modern Methods in Stereoselective Aldol Reactions

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The use of catalytic enantioselective methods to perform an aldol reaction provides a direct entry for the synthesis of chiral compounds and is probably the most attractive way to achieve this goal with high control of the chemo-, regio-, diastereo-, and enantioselectivity. The application of biochemical methods based on enzyme aldolases or antibodies, which are discussed in other chapters, avoid the use of preformed enolates or their equivalents for enhancing the global atom efficiency of the process [1] for which the narrow substrate scope is a major drawback. The discovery of methodologies to carry out the enantioselective direct aldol reaction [2] has eluded the production of stoichiometric by-products increasing the substrate scope. This task could be accomplished by using small molecules as catalysts, such as metal complexes (which are covered along this book) and organic molecules, also known as organocatalysts [3]. The growth of this last research area and the direct aldol reaction are closely linked [4], with the report on the use of (S)-proline as catalyst for the intermolecular aldol [5] definitely being the push for the development of the organocatalytic methods as a competitive methodology for the synthesis of chiral compounds.In a strict sense, an organocatalyzed reaction is a process in which all the involved reagents and catalysis are purely organic compounds of low-molecular weight, excluding boron-and silicon-containing derivatives. However, in some cases, the presence of a silyl group only plays a steric role and therefore can also be considered as an organocatalyzed process. Also, if the organocatalyst involved in a reaction is immobilized in a polymer, a dendrimer, or even an inorganic material that serves only as a support to facilitate its recovery [6], it could still be considered as an organocatalyst, although those types of derivatives have been scarcely used in the natural product synthesis and therefore will be excluded from this chapter. Therefore, a comprehensive overview of the direct aldol reaction [7], emphasizing the reactivity, scope, selectivity, and limitations of the methodology and giving several examples of their application to the synthesis of biologically active compounds, is discussed in this chapter.

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Section: Aldehydes As Electrophilesmentioning

confidence: 99%

Organocatalyzed Aldol Reactions

Guillena¹

2013

Modern Methods in Stereoselective Aldol Reactions

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“…The catalyst properties can be readily tuned by varying the stereo and electronic effects of the terminal amide to affect the ability of hydrogen bonding formation between the catalysts and the substrate. Strong electronwithdrawing nitro group was introduced to enhancing the amide NH acidity in the hope of improving stereocontrol [38][39][40][41].…”

Section: Introductionmentioning

confidence: 99%

l-Valine Dipeptide Organocatalysts with Two Amide Units for the Direct Asymmetric Aldol Reaction in Brine

Huang

Tian

et al. 2011

Catal Lett

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A series of valine dipeptide organocatalysts containing a primary amine group and two amide units have been developed and evaluated in the direct asymmetric intermolecular aldol reaction of 4-nitrobenzaldehyde and cyclohexanone. When 2,4-dinitrophenol (DNP) was used as an acidic additive, the catalyzed reactions of various aldehydes and ketones gave the corresponding aldol products with moderate to high enantioselectivities (up to 95%) and diastereoselectivities (up to [99/1, anti/ syn) in the presence of 3c in brine.

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“…Reaction between 4‐nitrobenzaldehyde ( 10 ) and cyclohexanone ( 11 ) in the presence of catalyst 63 afforded product ( 13 ) in 88% yield and anti/syn (98:2) with 98% ee . The catalysis is proceeding through enamine mechanism but additional effect of hydrogen bonding of amide with benzaldehyde is discussed (Scheme ) …”

Section: Prolinamide Catalysed Direct Asymmetric Aldol Reactionmentioning

confidence: 99%

Prolinamide‐Catalysed Asymmetric Organic Transformations

2019

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Proline was reported as an enantioselective organocatalyst for direct asymmetric aldol reaction in the early 1971 s by two independent groups of researchers and the reaction was called the Hajos‐Parrish‐Eder‐ Sauer Wiechert reaction. The breakthrough of enantioselective organocatalysis was demonstrated by List and co‐workers in 2000 for intermolecular aldol reaction between benzaldehydes and ketone using proline as a catalyst. After this report many researchers were applied the proline as a catalyst for other organic transformation. The proline has a carboxylic functional group which can easily convert to the amide and known as prolinamide. Prolinamides were found to be a better catalyst compared to proline in the most of cases. In this review article we are compiling the results of the prolinamides catalyzed asymmetric organic transformation with insight of the mechanism of catalysis.

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C₃‐Symmetric Proline‐Functionalized Organocatalysts: Enantioselective Michael Addition Reactions

Abstract: C3‐Symmetric, tripodal catalyst 4 based on 1,3,5‐triethylbenzene, which incorporates the features of a molecular receptor, is shown to catalyze Michael addition reactions ofcarbonyl compounds to β‐nitrostyrenes in a high stereoselectivity (up to 99:1 dr and up to 98 % ee).

Cited by 42 publications

References 65 publications

Organocatalyzed Aldol Reactions

Organocatalyzed Aldol Reactions

l-Valine Dipeptide Organocatalysts with Two Amide Units for the Direct Asymmetric Aldol Reaction in Brine

Prolinamide‐Catalysed Asymmetric Organic Transformations

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C3‐Symmetric Proline‐Functionalized Organocatalysts: Enantioselective Michael Addition Reactions

Abstract: C3‐Symmetric, tripodal catalyst 4 based on 1,3,5‐triethylbenzene, which incorporates the features of a molecular receptor, is shown to catalyze Michael addition reactions ofcarbonyl compounds to β‐nitrostyrenes in a high stereoselectivity (up to 99:1 dr and up to 98 % ee).

Cited by 42 publications

References 65 publications

Organocatalyzed Aldol Reactions

Organocatalyzed Aldol Reactions

l-Valine Dipeptide Organocatalysts with Two Amide Units for the Direct Asymmetric Aldol Reaction in Brine

Prolinamide‐Catalysed Asymmetric Organic Transformations

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C₃‐Symmetric Proline‐Functionalized Organocatalysts: Enantioselective Michael Addition Reactions