Residual Enantiomerism and Chromatographic Resolution of a 1,1,2‐Triarylalkene

A three‐ring flip A⇄B is the isomerization mechanism of lowest activation enthalpy for triarylalkene propeller molecules. NMR studies on 1, for which this mechanism leads to a diastereomerization rather than an enantiomerization, gave a value of 79.5 kJ mol ⁻¹ for this process. After chromatographic separation of the enantiomers of 1, it was also possible to determine the activation enthalpy of its enantiomerization, which presumably occurs by a [β,β′] two‐ring flip: 92.7 kJ mol⁻¹. (Figure Presented.)