Optimizing dirhodium(II) tetrakiscarboxylates as chiral NMR auxiliaries

J Mattiza, Joerg G.G. Fohrer, Helmut Duddeck, M Gardiner, Ashraf Ghanem

Research output: Contribution to journalArticle

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Abstract

Thirteen enantiopure paddlewheel-shaped dirhodium(II) tetrakiscarboxylate complexes have been checked for their efficiency in the dirhodium method (differentiation of enantiomers by NMR spectroscopy); six of them are new. Their diastereomeric dispersion effects were studied and compared via so-called key numbers KN. Adducts of each complex were tested with five different test ligands representing all relevant donor properties from strong (phosphane) to very weak (ether). Only one of them, the dirhodium complex with four axial (S)-N-2,3-naphthalenedicarboxyl-tert-leucinate groups (N23tL), showed results significantly better for all ligands than the conventional complex Rh* [Rh(II)2[(R)-(+)-MTPA]4; MTPA = methoxytrifluoromethylphenylacetate]. On the basis of 1H{1H} NOE spectroscopy and X-ray diffraction, a combination of favourable anisotropic group orientation and conformational flexibility is held responsible for the high efficiency of N23tL in enantiodifferentiation. Both complexes, Rh* and N23tL, are recommended as chiral auxiliaries for the dirhodium experiment.
Original languageEnglish
Pages (from-to)6542-6550
Number of pages9
JournalOrganic Molecular Chemistry
Volume9
Issue number19
DOIs
Publication statusPublished - 2011

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phosphine
Nuclear magnetic resonance
Ligands
nuclear magnetic resonance
Enantiomers
X-Ray Diffraction
Ether
Nuclear magnetic resonance spectroscopy
Spectrum Analysis
Magnetic Resonance Spectroscopy
Spectroscopy
X ray diffraction
ligands
enantiomers
spectroscopy
adducts
ethers
flexibility
Experiments
diffraction

Cite this

Mattiza, J ; Fohrer, Joerg G.G. ; Duddeck, Helmut ; Gardiner, M ; Ghanem, Ashraf. / Optimizing dirhodium(II) tetrakiscarboxylates as chiral NMR auxiliaries. In: Organic Molecular Chemistry. 2011 ; Vol. 9, No. 19. pp. 6542-6550.
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abstract = "Thirteen enantiopure paddlewheel-shaped dirhodium(II) tetrakiscarboxylate complexes have been checked for their efficiency in the dirhodium method (differentiation of enantiomers by NMR spectroscopy); six of them are new. Their diastereomeric dispersion effects were studied and compared via so-called key numbers KN. Adducts of each complex were tested with five different test ligands representing all relevant donor properties from strong (phosphane) to very weak (ether). Only one of them, the dirhodium complex with four axial (S)-N-2,3-naphthalenedicarboxyl-tert-leucinate groups (N23tL), showed results significantly better for all ligands than the conventional complex Rh* [Rh(II)2[(R)-(+)-MTPA]4; MTPA = methoxytrifluoromethylphenylacetate]. On the basis of 1H{1H} NOE spectroscopy and X-ray diffraction, a combination of favourable anisotropic group orientation and conformational flexibility is held responsible for the high efficiency of N23tL in enantiodifferentiation. Both complexes, Rh* and N23tL, are recommended as chiral auxiliaries for the dirhodium experiment.",
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Optimizing dirhodium(II) tetrakiscarboxylates as chiral NMR auxiliaries. / Mattiza, J; Fohrer, Joerg G.G.; Duddeck, Helmut; Gardiner, M; Ghanem, Ashraf.

In: Organic Molecular Chemistry, Vol. 9, No. 19, 2011, p. 6542-6550.

Research output: Contribution to journalArticle

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AB - Thirteen enantiopure paddlewheel-shaped dirhodium(II) tetrakiscarboxylate complexes have been checked for their efficiency in the dirhodium method (differentiation of enantiomers by NMR spectroscopy); six of them are new. Their diastereomeric dispersion effects were studied and compared via so-called key numbers KN. Adducts of each complex were tested with five different test ligands representing all relevant donor properties from strong (phosphane) to very weak (ether). Only one of them, the dirhodium complex with four axial (S)-N-2,3-naphthalenedicarboxyl-tert-leucinate groups (N23tL), showed results significantly better for all ligands than the conventional complex Rh* [Rh(II)2[(R)-(+)-MTPA]4; MTPA = methoxytrifluoromethylphenylacetate]. On the basis of 1H{1H} NOE spectroscopy and X-ray diffraction, a combination of favourable anisotropic group orientation and conformational flexibility is held responsible for the high efficiency of N23tL in enantiodifferentiation. Both complexes, Rh* and N23tL, are recommended as chiral auxiliaries for the dirhodium experiment.

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