Influence of the nature of chiral auxiliaries on the diastereoselective hydrogenation of ortho-substituted benzoic acid derivatives

Бессон, М.; Gallezot, P.; Neto, Samuel; Pinel, Catherine

doi:10.1016/s0957-4166(00)00112-9

Cited by 17 publications

(8 citation statements)

References 10 publications

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“…Fig 3b). This better control of the NPs growth could result from the pre-stabilization of Ru 0 hydrosol with hydronium ions or other hydrated ions (H 5 [53] Moreover, in comparison with Ru 0 @RaMeCD systems, [46] these NPs exhibited smaller diameters. As previously mentioned, [53,54] this phenomenon could be explained by the protonation of Ala or Leu moieties at pH of medium (~4.9), thus producing ammonium forms that may reinforce the NPs stability within aqueous solution thanks to coulombic interactions [55,56] while the RaMeCD backbone provides only a steric stabilization.…”

Section: Characterisation Of Ruthenium(0) Nanoparticlesmentioning

confidence: 99%

“…Optically active cyclohexyl moieties play a key role in the synthesis of various biologically active molecules or auxiliaries. [1] Among the various strategies, enzymatic or chemical resolution approaches [2] or chiral auxiliarybound substrates [3][4][5][6] were used to produce these optically enriched intermediates. An elegant alternative method will rely on the catalytic diastereoselective hydrogenation of monocyclic polysubstituted benzenes.…”

Section: Introductionmentioning

confidence: 99%

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β-Cyclodextrins grafted with chiral amino acids: A promising supramolecular stabilizer of nanoparticles for asymmetric hydrogenation?

Chau¹,

Guégan²,

Menuel³

et al. 2013

Applied Catalysis A: General

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International audienceWater-soluble ruthenium nanoparticles stabilized by randomly methylated β-cyclodextrins (RaMeCDs) grafted with chiral amino-acid moieties like l-alanine (Ala) and l-leucine (Leu) were prepared in aqueous solution by two approaches: (i) a one-step hydrogen reduction of ruthenium trichloride as metal source in the presence of appropriate cyclodextrins (one-pot method) or (ii) a NaBH4 reduction of the metal salts, followed by the stabilization of ruthenium hydrosol by the addition of chirally modified RaMeCDs (cascade method). The influence of the ligand's nature and the synthesis methodologies on the size, dispersion and surface properties of the obtained ruthenium colloids were studied by TEM and NMR analyses. The spherical ruthenium suspensions contain very small particles (0.82-1.00 nm) with narrow size distributions. Their catalytic properties were evaluated in biphasic hydrogenation of various prochiral compounds (olefins, ketones and disubstituted arenes) showing promising results in terms of activity and selectivity. Nevertheless, no significant enantiomeric excesses were observed

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Section: Characterisation Of Ruthenium(0) Nanoparticlesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

β-Cyclodextrins grafted with chiral amino acids: A promising supramolecular stabilizer of nanoparticles for asymmetric hydrogenation?

Chau¹,

Guégan²,

Menuel³

et al. 2013

Applied Catalysis A: General

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“…Indeed, the hydrogenation of (S)-N -(2-methylbenzoyl)-prolinol was much slower than with the proline derivative, and the d.e. was moderate (<20%; [110]. The pantolactone derivative is not rigid enough as the chiral auxiliary is linked through an ester bond instead of an amide bond.…”

Section: Diastereoselective Hydrogenation Of Aromatic Ringsmentioning

confidence: 99%

Diastereoselective Catalysis

Бессон

Pinel

2008

Handbook of Heterogeneous Catalysis

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IntroductionA reaction is referred to as stereoselective when a substrate S, which may yield a series of stereoisomer products (P 1 , P 2 , . . . P n ) gives preferentially -or even exclusively -one of these. Today, the preparation of stereoisomeric compounds is generating tremendous academic and industrial interest. Especially, the synthesis of enantiopure chiral compounds is becoming increasingly important in the production of pharmaceuticals, agrochemicals, fragrances, and flavor substances. Among the different methods used to prepare pure enantiomers, asymmetric catalysis plays an important role, particularly hydrogenation. Currently, two types of asymmetric hydrogenation with solid catalysts are utilized, namely enantioselective and diastereoselective synthesis.In enantioselective hydrogenation, one enantiomer of a chiral product is formed preferentially from a prochiral precursor, the stereoselectivity being induced by a chiral catalyst. Immobilization of very selective metal-ligand complexes and modification of active metals by an adsorbed chiral organic molecule (chiral modifier) have been extensively studied [1]. In some cases, high enantioselectivities approaching 98% enantiomeric excess (e.e.) have been obtained with modified supported metal catalysts. The numerous investigations devoted to the understanding of the mechanism have been summarized in several reviews [1][2][3][4][5]. The most effective catalysts are Ni-tartaric acid, Pt-cinchona, Pd-cinchona and, to a lesser extent, Rh-cinchona systems. The field of reaction types is still limited to a narrow range of asymmetric hydrogenations.The other frequently used catalytic strategy for the synthesis of pure enantiomers is based on diastereoselective hydrogenation. This involves the selective formation of one diastereoisomer by creating a new stereogenic center in a chiral molecule. In this approach, the reaction consists of three simple steps. First, a covalent bond between the prochiral substrate and a chiral moiety (chiral auxiliary) is formed. Then, the diastereoselective hydrogenation is performed over various noble metal catalysts, leading stereoselectively to a new chiral center. This step does not require a chiral catalyst, but the stereogenic center in the chiral auxiliary is able to induce the stereoselectivity. The desired molecule can finally be obtained by selective cleavage of the chiral auxiliary from the product which can be recycled.

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“…Reduction of α,βunsaturated sultams has been shown to give the highest levels of diastereoselectivity using hydrogenation conditions 367 while the diastereoselective hydrogenation of ortho-substituted benzoic acid derivatives has been shown to be most effective using a pyroglutamic acid derivative. 368 Asymmetric Birch reduction followed by quenching with methyl iodide has been optimised using proline-based auxiliaries 72 capable of controlling the intermediate enolate geometry by hindered rotation (Scheme 47). 369 Products 73 with diastereomeric ratios of 93 : 7 have been obtained in this way.…”

Section: Scheme 46mentioning

confidence: 99%

Stoichiometric asymmetric processes

Jones

2001

J. Chem. Soc., Perkin Trans. 1

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Influence of the nature of chiral auxiliaries on the diastereoselective hydrogenation of ortho-substituted benzoic acid derivatives

Cited by 17 publications

References 10 publications

β-Cyclodextrins grafted with chiral amino acids: A promising supramolecular stabilizer of nanoparticles for asymmetric hydrogenation?

β-Cyclodextrins grafted with chiral amino acids: A promising supramolecular stabilizer of nanoparticles for asymmetric hydrogenation?

Diastereoselective Catalysis

Stoichiometric asymmetric processes

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