ChemInform Abstract: Dynamic Kinetic Resolution in the Asymmetric Synthesis of β‐Amino Acids by Organocatalytic Reduction of Enamines with Trichlorosilane.

Malkov, Andrei V.; Stončius, Sigitas; Vranková, Kvetoslava; Arndt, Matthias; Kočovský, Pavel

doi:10.1002/chin.200905060

Cited by 3 publications

(3 citation statements)

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“…The catalyst 2c has very recently also proved to be suitable for the development of a new protocol for the enantioselective synthesis of β‐amino acid derivatives from enamine precursors (Scheme ) 18. Treatment of β‐ketoesters/‐nitriles with p ‐anisidine afforded enamines, which themselves cannot be reduced by Cl 3 SiH.…”

Section: Discussionmentioning

confidence: 99%

Trichlorosilane‐Mediated Stereoselective Reduction of C=N Bonds

2010

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The reduction of C=N bonds represents a powerful and widely used transformation allowing new nitrogen‐containing stereocenters to be generated. Chiral amino groups are ubiquitous in a variety of bioactive molecules such as alkaloids, natural products, drugs, and medical agents, so the development of a catalytic stereoselective process for the preparation of enantiomerically enriched amines through ketoimine reduction is attracting increasing interest, especially in view of future industrial applications. Great efforts to develop efficient organocatalytic methods to perform enantioselective imine reductions and reductive amination processes have recently been made. In the last few years, trichlorosilane‐mediated reductions have received constantly increasing attention because the potential to generate chiral catalysts for imine reduction simply by coordination of HSiCl3 with a chiral Lewis base has allowed the development of several efficient organocatalytic systems. Here we offer a complete overview of different chiral promoters of stereoselective reductions with trichlorosilane, classified as N‐formyl derivatives, which may be considered historically the first class of compounds developed as chiral activators of trichlorosilane, picolinamide derivatives, and miscellaneous compounds presented in that order.

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Section: Discussionmentioning

confidence: 99%

Trichlorosilane‐Mediated Stereoselective Reduction of C=N Bonds

2010

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“…38 The authors noted that pivotal for the activity and selectivity of the catalyst was the introduction of precise quantities (1 equivalent) of acetic acid, it's role being suggested to facilitate tautomerisation of the β-enamino ester/nitrile to the imine form, the active substrate for hydrosilylation. 38 The authors noted that pivotal for the activity and selectivity of the catalyst was the introduction of precise quantities (1 equivalent) of acetic acid, it's role being suggested to facilitate tautomerisation of the β-enamino ester/nitrile to the imine form, the active substrate for hydrosilylation.…”

Section: Methodsmentioning

confidence: 99%

Trichlorosilane mediated asymmetric reductions of the CN bond

2012

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Chiral amines are key components in numerous bioactive molecules. The development of efficient and economical ways to access molecules containing this functional group still remains a challenge at the forefront of synthetic chemistry. Of the methods that do exist, the trichlorosilane mediated organocatalytic reduction of ketimines offers significant potential as an alternative strategy. In this perspective, we wish to highlight the progress made in the past decade in this field and offer a direct quantitative comparison to transition-metal mediated process.

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“…However, there is only limited examples of enantioselective hydrosilylation of β‐enamino esters 7b. 8 To our knowledge, a general, highly enantioselective Lewis base organocatalyzed hydrosilylation of β‐enamino esters has not been reported, and thus remains an important challenge.…”

Section: Methodsmentioning

confidence: 99%

Highly Enantioselective Synthesis of β‐Amino Acid Derivatives by the Lewis Base Catalyzed Hydrosilylation of β‐Enamino Esters

Zheng

Chen

et al. 2008

Chemistry A European J

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Optically active b-amino acids are very important chiral building blocks for the synthesis of b-peptides, b-lactams, natural products, and physiologically active substances. [1] Therefore, efficient methods for the synthesis of optically active b-amino acids would be of great value for drug discovery and organic synthesis. Among the approaches to chiral b-amino acids, [2] the most straightforward and atom economic one is catalytic asymmetric reduction of b-enamino esters. Pioneered by Noyori et al., [3a] many chiral transition-metal complexes were developed to catalyze high-pressure hydrogenation of N-acyl b-enamino esters, [3] N-aryl benamino esters, [4] or N-unprotected b-enamino esters [5] with high enantioselectivities. However, transition-metal-catalyzed hydrogenation cannot get rid of the problems of metal leaching, high pressure, the cost of the catalyst, and its regeneration.Recently, asymmetric reactions involving the strategy of Lewis base activation of Lewis acids attracted much attention.[6] Among these reactions, Lewis base catalyzed enantioselective hydrosilylation of ketimines has become an important alternative to transition-metal catalysis in synthesis of chiral amines.[7] However, there is only limited examples of enantioselective hydrosilylation of b-enamino esters. [7b, 8] To our knowledge, a general, highly enantioselective Lewis base organocatalyzed hydrosilylation of b-enamino esters has not been reported, and thus remains an important challenge.Herein, we describe the first general, highly enantioselective organocatalytic hydrosilylation of b-enamino esters. Matsumura and co-workers reported the hydrosilylation of unprotected b-enamino ester 1 a catalyzed by N-picolinoylpyrrolidine derivative 2 a that resulted in poor yield and enantioselectivity (Scheme 1).[7b] However, to our delight, we found that the same catalyst 2 a and its analogues displayed excellent activities and enantioselectivities in promoting hydrosilylation of N-aryl b-enamino esters.First, N-picolinoylpyrrolidine derivatives 2 a-2 e and N-picolinoylephedrine (4) [7m] were evaluated in hydrosilylation of (Z)-methyl 3-phenyl-3-(phenylamino)acrylate.[9] As can be seen in

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ChemInform Abstract: Dynamic Kinetic Resolution in the Asymmetric Synthesis of β‐Amino Acids by Organocatalytic Reduction of Enamines with Trichlorosilane.

Abstract: Amines Q 0120 Dynamic Kinetic Resolution in the Asymmetric Synthesis of β-Amino Acids by Organocatalytic Reduction of Enamines with Trichlorosilane. -(MALKOV*, A. V.; STONCIUS, S.; VRANKOVA, K.; ARNDT, M.; KOCOVSKY, P.; Chem. Eur. J. 14 (2008) 27, 8082-8085; Dep. Chem.,

Cited by 3 publications

References 1 publication

Trichlorosilane‐Mediated Stereoselective Reduction of C=N Bonds

Trichlorosilane‐Mediated Stereoselective Reduction of C=N Bonds

Trichlorosilane mediated asymmetric reductions of the CN bond

Highly Enantioselective Synthesis of β‐Amino Acid Derivatives by the Lewis Base Catalyzed Hydrosilylation of β‐Enamino Esters

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