Enantiomerization at sulfur, selenium and tellurium stereogenic centres: studies by dynamic chiral liquid chromatography and chiroptical methods.

While it has been shown that enantiomerization of chiral tri- and tetracoordinate sulfur compounds can take place via a variety of different mechanisms, much less is known concerning the corresponding selenium and tellurium analogues. Studies of the stereochemical integrity of heteroatom centers have often been hampered by the lack of access to, or the instability of, optically active material and most investigations have been made on epimerization reactions, i.e. diastereomer interconversions. By the application of dynamic chromatography on a chiral stationary phase, particularly dynamic LC, however, enantiomerization rates can be estimated without any isolation of the individual enantiomers. In addition to chiroptical methods, we have applied this technique, which involves a comparison of simulated and experimental chromatograms, to the study of some stereolabile S, Se and Te compounds in order to learn more about their enantiomerization mechanisms.