Carbon-13 NMR spectra of 3-aryl-2-thioxo-4-imidazolidinones. Conformational isomerism and substituent effects

A ¹³C NMR study of a series of 3-aryl-2-thioxo-4-imidazolidinones, which are capable of existing as enantiomeric or diastereomeric rotational isomers about the aryl C? N bond, shows that rates of internal rotation are slow at the probe temperature. The effects of hetero- and aryl-ring substituents on hetero-ring carbon atoms have been established.