NMR-based Enantiodifferentiation of Chiral trans-2-Phenylcyclopropane Derivatives Using a Chiral Lanthanide Shift Reagent

Cho, Nam Sook; Kim, Hyun Sook; Song, Mi Sook

doi:10.5012/bkcs.2011.32.6.2076

Cited by 3 publications

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“…Presumably because of their relatively labile coordination bonds, the rotaxanes 3 ·2TFPB and 5· TFPB, which we had isolated using flash chromatography, were both unstable under the conditions of high-performance liquid chromatography (HPLC), making it impractical to resolve them through chiral HPLC. Nevertheless, the addition of 10 equiv of europium tris[3-(trifluoromethylhydroxymethylene)-(+)-camphorate] [Eu(tfc) 3 ] or tetrabutylammonium Δ-tris(tetrachloro-1,2-benzenediolato)phosphate(V) (Bu 4 N· Δ -TRISPHAT) to a solution of the rotaxane 5· TFPB (1.8 mM) in CD 2 Cl 2 allowed us to differentiate the enantiomers through 1 H NMR spectroscopy at 233 and 298 K, respectively, by splitting of the two doublets for the methylene protons (H Ĺ́ and H ĺ́ ) located between the pyridyl ring and the noncoordinating tertiary amino group into two nearby sets (Figure S2). Interestingly, europium tris[3-(heptafluoropropylhydroxymethylene)-(+)-camphorate] [Eu(hfc) 3 ] was less sensitive to 5· TFPB but practical for resolution of the rotaxane 3 ·2TFPB.…”

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Metal-Ion-Induced Mechanical Chirality: Achiral Rotaxane as the Only Ligand in Chiral Palladium(II)–N-Heterocyclic Carbene Complexes

et al. 2022

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We report the insertion of Pd(II) into an originally achiral rotaxane producing two chiral metallorotaxanes: one is planar-chiral, with its two interlocked components both chelating nonequivalently to the metal center; the other is C 2 -symmetricalchiral, with the dynamically exchangeable stereogenic units stabilized by the interlocked structure. Chiral additives confirmed the existence of chirality, with the enantiomers of the C 2 -symmetrical N-heterocyclic carbene complex being resolved using chiral TRISPHAT counteranions.Letter pubs.acs.org/OrgLett

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Metal-Ion-Induced Mechanical Chirality: Achiral Rotaxane as the Only Ligand in Chiral Palladium(II)–N-Heterocyclic Carbene Complexes

et al. 2022

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Advances in the use of Lanthanide Enolates as Nuclear Magnetic Resonance Shift Reagents

Wenzel

Patton

2016

Patai's Chemistry of Functional Groups

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The use of lanthanide enolates as NMR shift reagents is described. Strategies to reduce broadening in the NMR spectrum with paramagnetic lanthanide ions are discussed. Recent studies of achiral donors are presented. Recent studies in which lanthanide enolates are used for structural and conformation analysis are described. The use of paramagnetic and diamagnetic chiral lanthanide complexes for analysis of enantiopurity by NMR spectroscopy is discussed. Recent studies in which NMR spectroscopy is used to characterize lanthanide β‐diketonate complexes are described.

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Chiral Derivatizing Agents, Macrocycles, Metal Complexes, and Liquid Crystals for Enantiomer Differentiation in NMR Spectroscopy

Wenzel

2013

Topics in Current Chemistry

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Enantiomerically pure chiral auxiliary agents are often used in NMR spectroscopy to facilitate the differentiation of enantiomers. Chiral derivatizing agents are covalently bound to the substrate and differences in chemical shifts of the resulting diastereomeric complexes are used in the analysis. Macrocycles such as cyclodextrins, crown ethers, and calix[4]resorcinarenes are chiral solvating agents that associate with the substrate through non-covalent interactions. Enantiomeric differentiation occurs in the NMR spectrum because of the diastereomeric nature of the associated complexes and/or because of the differences in association constants between the two enantiomers and the chiral reagent. Metal complexes are Lewis acids that bind to suitable Lewis base donor compounds. Exchange of substrate can be slow or fast depending on the particular metal ion, mimicking the behavior of a chiral derivatizing or solvating agent, respectively. Chiral liquid crystals undergo a partial alignment in an applied magnetic field and enantiomers dissolved in the liquid crystal undergo a partial alignment as well. If the alignment of the two enantiomers is different, enantiomeric differentiation can potentially be observed by differences in chemical shifts, differences in dipolar coupling constants, and different magnitudes of splitting of quadrupolar nuclei such as deuterium. The chiral reagents described herein can be used to determine enantiomeric composition and sometimes to assign absolute configuration. Significant discoveries as well as recent findings with each of these types of systems are described.

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NMR-based Enantiodifferentiation of Chiral trans-2-Phenylcyclopropane Derivatives Using a Chiral Lanthanide Shift Reagent

Cited by 3 publications

References 20 publications

Metal-Ion-Induced Mechanical Chirality: Achiral Rotaxane as the Only Ligand in Chiral Palladium(II)–N-Heterocyclic Carbene Complexes

Metal-Ion-Induced Mechanical Chirality: Achiral Rotaxane as the Only Ligand in Chiral Palladium(II)–N-Heterocyclic Carbene Complexes

Advances in the use of Lanthanide Enolates as Nuclear Magnetic Resonance Shift Reagents

Chiral Derivatizing Agents, Macrocycles, Metal Complexes, and Liquid Crystals for Enantiomer Differentiation in NMR Spectroscopy

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