ABSTRACT
The 1H, 13C, and 31P NMR signals of six chiral phospholene chalcogenides (X = O, S, Se) are duplicated in the presence of one mole equivalent of the chiral auxiliary Rh2[(R)-MTPA]4 (diastereomeric dispersion Deltanu; in Hz). The samples were investigated as nonracemic mixtures of enantiomers with known absolute configurations so that signs can be attributed to the Deltanu-values and each signal set can be assigned to the respective enantiomer. The signs are uniform--in particular those of 1H nuclei--and nearly independent of the nature of the chalcogen atom. Thus, if the absolute configuration of one compound is known, it is possible to derive absolute configurations in the whole series (correlation method).
Subject(s)
Chalcogens/chemistry , Organophosphorus Compounds/chemistry , Rhodium/chemistry , Acetone/chemistry , Cadmium Chloride/chemistry , Chalcogens/analysis , Chalcogens/chemical synthesis , Magnetic Resonance Spectroscopy , Molecular Conformation , Molecular Structure , Organophosphorus Compounds/analysis , Organophosphorus Compounds/chemical synthesis , Phosphoric Acids/chemistry , Reference Standards , Rhodium/analysis , Solubility , StereoisomerismABSTRACT
Full NMR spectral assignments of the phospholene chalcogenides 1-12 are presented and their stereochemistry proven. The enantiomeric ratio of any of these compounds can be monitored easily by adding one mole equivalent of the chiral auxiliary Rh(2)[(R)-MTPA](4) (MTPA-H identical with Mosher's acid) and subsequent NMR inspection. Some surprisingly large diastereomeric signal dispersion is observed in the (1)H NMR spectra of the adducts, leading to the conclusion that intramolecular anisotropy interaction between groups inside the ligand molecules exists. The dependence of dispersion effects on the nature of the chalcogenide atom is investigated.
