Atropisomeric 3-aryl-2-oxo-4-oxazolidinones and some thione analogues-Enantiodifferentiation and ligand competition in applying the dirhodium method

The atropisomeric 2‐oxo‐4‐oxazolidinones 1Z bind weakly to the rhodium atoms in the complex Rh (II)2[(R)‐(+)‐MTPA]4 (Rh*, MTPA‐H = methoxytrifluoromethylphenylacetic acid ≡ Mosher's acid), presumably via the C‐2 carbonyl oxygen atom. There are some 1H and 13C NMR signals in these compounds whic...

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Bibliographic Details
Published in:Chirality (New York, N.Y.) N.Y.), 2008-03, Vol.20 (3-4), p.344-350
Main Authors: Gómez, Edison Díaz, Doğan, İlknur, Yilmaz, Müjde, Demir-Ordu, Öznur, Albert, Dieter, Duddeck, Helmut
Format: Article
Language:English
Subjects:
1H and 13C NMR
3-aryl-2-oxo-4-oxazolidinone derivatives
adduct formation
atropisomerism
axial chirality
chiral recognition
dirhodium complexes
rhodanines
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Summary:The atropisomeric 2‐oxo‐4‐oxazolidinones 1Z bind weakly to the rhodium atoms in the complex Rh (II)2[(R)‐(+)‐MTPA]4 (Rh*, MTPA‐H = methoxytrifluoromethylphenylacetic acid ≡ Mosher's acid), presumably via the C‐2 carbonyl oxygen atom. There are some 1H and 13C NMR signals in these compounds which show small dispersion effects suitable for enantiodifferentiation. In contrast, the thiocarbonyl sulfur atoms in 2Z and 3Z bind strongly so that significant complexation shifts (Δδ) and diastereomeric dispersion effects (Δν) can be observed, and chiral discrimination and the determination of enantiomeric ratios of these thiocarbonyl compounds is easy. So, it is shown that—as expected—CS is a much better binding site when competing with CO. In compounds of Series 2 a “syn‐methyl effect” was discovered which describes the dependence of dispersion effects of syn‐oriented methyl groups 6 on the nature of the substituents Z. A mechanism of combined steric and electronic interaction influencing the conformational equilibria inside the adducts is proposed. Determination of absolute configurations by correlation fails, at least on the basis of the data available. Chirality, 2008. © 2007 Wiley‐Liss, Inc.
ISSN:0899-0042
1520-636X
DOI:10.1002/chir.20446