Conjugated Azomethine Ylides

Melo, Teresa M. V. D. Pinho e

doi:10.1002/ejoc.200500892

Cited by 148 publications

(27 citation statements)

References 73 publications

(66 reference statements)

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“…[11] However, under these reaction conditions [[Cu(CH 3 CN) 4 ]PF 6 (10 mol %), fesulphos ligand (3; 10 mol %), and Et 3 N (18 mol %) in CH 2 Cl 2 at room temperature] we observed the formation of a complex mixture of isomers. [14] In an attempt to improve the selectivity of the cycloaddition we next turned to using the diastereoisomeric dipolarophile, methyl (Z)-3-phenylsulfonylpropenoate (2).…”

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confidence: 92%

“…[3] In this context, the metalcatalyzed asymmetric [3+2] cycloaddition of stabilized azomethine ylides with electron-deficient alkenes has emerged as one of the most convergent and atom-economical tools for the enantioselective synthesis of pyrrolidine and proline-type derivatives. [4,5] The regioselectivity in the cycloaddition of stabilized Nmetalated azomethine ylides (usually derived from glycine esters) with unsymmetrically substituted electron-deficient olefins is controlled by electronic effects, leading to pyrrolidine rings, which are substituted at the 2-and 4-positions, as the sole product.[6] However, this excellent regiocontrol hampers the preparation of the regioisomeric pyrrolidine rings with electron-withdrawing substituents at the 2-and 3-positions. This type of structural unit is frequently found in natural, and biologically active compounds.…”

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confidence: 99%

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The Phenylsulfonyl Group as a Temporal Regiochemical Controller in the Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of Azomethine Ylides

2008

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Pyrrolidine derivatives are a significant group of heterocycles which are present in an array of natural and synthetic biologically active products.[1] Furthermore, proline analogues have applications as chiral ligands and as organocatalysts in asymmetric synthesis.[2] This synthetic and biological relevance has encouraged the development of efficient routes for the stereoselective and enantioselective preparation of substituted pyrrolidines. [3] In this context, the metalcatalyzed asymmetric [3+2] cycloaddition of stabilized azomethine ylides with electron-deficient alkenes has emerged as one of the most convergent and atom-economical tools for the enantioselective synthesis of pyrrolidine and proline-type derivatives. [4,5] The regioselectivity in the cycloaddition of stabilized Nmetalated azomethine ylides (usually derived from glycine esters) with unsymmetrically substituted electron-deficient olefins is controlled by electronic effects, leading to pyrrolidine rings, which are substituted at the 2-and 4-positions, as the sole product.[6] However, this excellent regiocontrol hampers the preparation of the regioisomeric pyrrolidine rings with electron-withdrawing substituents at the 2-and 3-positions. This type of structural unit is frequently found in natural, and biologically active compounds. For instance, 2,3-dicarboxylic acid substituted pyrrolidine units are potent and selective inhibitors of glutamate receptors and glutamate transporters, [7] and they have been used in the design of new peptides and constrained peptidomimetics.[8] Taking into account that most methods currently used in the preparation of pyrrolidines with 2,3-dicarboxylic acid substitution are based on multistep approaches from a-amino acid precursors, [9] the development of more convergent synthetic strategies is highly desirable.We have recently reported that unsubstituted vinyl sulfones [10] and bis(sulfonyl)ethylenes [11] are excellent dipolarophiles in the catalytic asymmetric 1,3-dipolar cycloaddition of azomethine ylides. Bearing in mind the excellent properties of the sulfonyl group both as a powerful electronwithdrawing group and as an easily removed substituent, [12] we envisaged that the regioselectivity of the catalytic asymmetric reaction of sulfonyl acrylates with azomethine ylides derived from iminoesters could be controlled by the sulfonyl moiety rather than the ester group, [13] and lead to the regioselective and stereoselective formation of 2,3-dicarboxylic acid substituted pyrrolidines (Scheme 1). Herein, we describe the scope of this strategy and its application to the enantioselective synthesis of a variety of 2,3-dicarboxylic ester substituted pyrrolidines and derivatives.First, we carried out the reaction of methyl (E)-3-phenylsulfonylpropenoate and N-benzylideneglycine methyl ester (1 a) under the optimal reaction conditions previously reported by us for the copper-catalyzed 1,3-dipolar cycloaddition of azomethine ylides and bis(sulfonyl)ethylenes. [11] However, under these reaction conditions [[Cu(CH 3 CN) 4 ]...

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confidence: 92%

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confidence: 99%

The Phenylsulfonyl Group as a Temporal Regiochemical Controller in the Catalytic Asymmetric 1,3‐Dipolar Cycloaddition of Azomethine Ylides

2008

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“…[4] Regarding N-ylides, the most intensive attention has always been paid to azomethine ylides and the conjugated azomethine ylides with a double bond or a 1,4-diene moiety, which was reported by Pinho e Melo in 2006. [5] Among the N-ylides, N-imide ylides have recently attracted attention for incorporating a nitrogen atom into molecules for the synthesis of nitrogen-containing structures. N-Imide ylides are more stable than other N-ylides, due to the carbonyl N-protecting groups.…”

Section: Introductionmentioning

confidence: 99%

N‐Imide Ylide‐Based Reactions: CH Functionalization, Nucleophilic Addition and Cycloaddition

Qiu

Kuang

2014

Adv Synth Catal

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As valuable building blocks for introducing nitrogen, N-imide ylides represent an important class of reactive species and are synthons for the synthesis of nitrogen-containing heterocycles that potentially have biological activities. During the past decades, tremendous efforts have been devoted to the tandem processes involving N-imide ylides as well as their asymmetric applications. In particular, several types of N-imide ylide-based reactions have been established, such as C À H functionalization, nucleophilic addition, and cycloaddition, etc. In this review, recent advances in N-imide ylides chemistry are presented ordered according to the sequence of various reaction types.

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“…1e5 Despite various known contributions to the chemistry of these building blocks, their use in 1,3-dipolar cycloadditions either as dipolarophiles or 1,3-dipole precursors is a less explored research area. 5 Nevertheless, allenes have been used to generate cyclic and acyclic nitrones through the reaction with hydroxylamines. 6 On the other hand, the main strategy to obtain 4-isoxazolines (2,3-dihydroisoxazoles) has been the 1,3-dipolar cycloaddition between nitrones and alkynes or allenes.…”

Section: Introductionmentioning

confidence: 99%