H-1 AND C-13 NMR-STUDIES ON 3-ARYL-5-ALKYL-2,4-OXAZOLIDINEDIONES - MAGNETIC NONEQUIVALENCE OF ISOMERIC NUCLEI

Magnetic non‐equivalence of diastereotopically related proton and 13C nuclei in enantiomeric and diastereomeric rotational isomers of 3‐aryl‐5‐alkyl‐2,4‐oxazolidinedlones has been investigated. Steric interactions between the aryl and the heterocyclic moieties of these compounds produce sufficient restriction to rotation about the aryl CN bond that the presence of torsional isomers may be detected at normal temperatures. Free energies of activation for rotation have been calculated. Chemical shift differences, associated with rotational isomerism, may be detected for both the proton and the 13C nuclei on the hetero ring, but only in the 13C spectra of the nuclei on the aryl moiety. Copyright © 1979 Heyden & Son Ltd.