Chiral recognition of ethers by NMR spectroscopy

Duddeck, H.; Gómez, Edison Díaz

doi:10.1002/chir.20605

Cited by 43 publications

(16 citation statements)

References 101 publications

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“…This is due to coalescence phenomena which have been discussed by us before. 3 If line broadening is hindering a safe determination of enantiomeric excess (ee), it can be removed or at least alleviated by heating the sample up to 40-508C.…”

Section: Resultsmentioning

confidence: 99%

“…4 Ligands L form kinetically labile 1:1-or 2:1-adducts with Rh1 depending on their relative molar composition (Scheme 2); ligand exchange rates are generally high relative to the NMR time-scale so that time-averaged NMR signals are observed at room temperature. 1:1-Adducts prevail under the so-called standard dirhodium experiment conditions, i.e., equimolar amounts of Rh1 and L, dissolved in CDCl 3 .…”

Section: Introductionmentioning

confidence: 99%

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Comparing various chiral dirhodium tetracarboxylates in the dirhodium method

et al. 2009

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Three enantiopure dirhodium tetracarboxylates are compared in their NMR properties to differentiate chiral ligands of various kinds (dirhodium method). The complex with four (S)-2-methoxy-2-(1-naphthyl) propionate (MalphaNP) residues (Rh2) is slightly better for strong donors than the complex with four Mosher acid anions (Rh1), but it is inferior for weak donors. On the other hand, the dirhodium tetracarboxylate complex with four (S)-N-phthaloyl-(S)-tert.-leucinate residues (Rh3) is generally more effective than Rh1. These results are explained by the estimated conformational behavior of the substituents within the equatorial acid residues and the anisotropy (ring-current) effect of aryl groups.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparing various chiral dirhodium tetracarboxylates in the dirhodium method

et al. 2009

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“…Araliphatic ethers [7] and thioethers (compounds 1 and 2, respectively, in Scheme 2) were chosen as candidates. Ethers form rather weak adducts with Rh * [7,8] and the binding energy is expected to be based primarily on electrostatic interaction. Orbital [highest occupied molecular orbital (HOMO)-LUMO] interaction does not contribute significantly if oxygen, as a secondrow element, is involved; the HOMO-LUMO gap is too large.…”

Section: Binding Sites and Adduct Formationmentioning

confidence: 99%

Experimental verification of diverging mechanisms in the binding of ether, thioether, and sulfone ligands to a dirhodium tetracarboxylate

Mattiza

Meyer

Duddeck

2010

Magnetic Reson in Chemistry

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Complexation of the oxygen atom in 2-butylphenylethers and sulfur in 2-butylphenylthioethers to a rhodium atom in dirhodium tetracarboxylate Rh((II)) (2)[(R)-(+)-MTPA](4) is compared. Oxygen atoms complex via electrostatic attraction exclusively leading to an increase in alpha effects on C-2 complexation shifts in the sequence OCH(3) > F > Br > NO(2). However, that trend is opposite in thioethers. This can be rationalized by an additional highest occupied molecular orbital (HOMO)-LUMO interaction and the response of this interaction upon complex formation shifts. Thereby, an experimental evidence was found for the existence of the HOMO-LUMO binding mechanism which has been proposed previously based on theoretical considerations and indirect spectroscopic evidence. Sulfones hardly bind to Rh((II)) (2)[(R)-(+)-MTPA](4). Diastereomeric dispersion effects at (13)C and (1)H signals can be observed for all compounds indicating that enantiodifferentiation is easy in all classes of functionalities.

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“…In NMR spectroscopy, three main protocols are used: chiral derivatization agents (CDA) [9,10], chiral lanthanide shift reagents (CLSR) [9][10][11] and chiral solvating agents (CSA) [9][10][11][12]. These methods rely on formation of diastereomeric complexes (between chiral resolving agent and analyte either through covalent or non-covalent coupling), which differ in the chemical shifts of some or all of their proton resonances.…”

Section: Introductionmentioning

confidence: 99%

Dynamic Processes in Prochiral Solvating Agents (pro-CSAs) Studied by NMR Spectroscopy

et al. 2014

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Several dynamic processes, including tautomerism and macrocyclic inversion, in 1H-NMR prochiral solvating agents (pro-CSAs) are investigated. Various features of pro-CSA, including modes of interaction for complex formation, stoichiometry, binding strength and temperature effects were compared for three representative pro-CSA molecules. Structural effects of conjugated tetrapyrrole pro-CSA on the mechanism of enantiomeric excess determination are also discussed. Detailed analysis of species (complexes) and dynamic processes occurring in solution and their 1H-NMR spectral manifestations at various temperatures is presented.

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Chiral recognition of ethers by NMR spectroscopy

Cited by 43 publications

References 101 publications

Comparing various chiral dirhodium tetracarboxylates in the dirhodium method

Comparing various chiral dirhodium tetracarboxylates in the dirhodium method

Experimental verification of diverging mechanisms in the binding of ether, thioether, and sulfone ligands to a dirhodium tetracarboxylate

Dynamic Processes in Prochiral Solvating Agents (pro-CSAs) Studied by NMR Spectroscopy

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