Conformational Studies by Dynamic NMR. 100. Enantiomerization Process of Stereolabile Atropisomers in Pyridine-Substituted Adamantane Derivatives

The barriers for interconverting the conformational enantiomers (stereolabile atropisomers) of pyridine-substituted adamantane derivatives have been determined by dynamic 13C NMR spectroscopy. The trend of these values parallels that anticipated by MM calculations. In at least one case, the computed structure was found to agree with that obtained by single-crystal X-ray diffraction. In addition, it has been possible to achieve a physical separation of a pair of these stereolabile atropisomers at −60 °C by means of the enantioselective cryogenic HPLC technique.