Resolution and Enantiomerization Barrier of Tetramesitylethylene

Article abstract of DOI:10.1021/jo00039a033

The 1H NMR spectrum of tetramesitylethylene (2) was analyzed, and the signals were assigned by means of a 2D NOESY spectrum.Attempts to observe anisochrony of the enantiotopic groups of a racemic mixture of 2 in a chiral solvent by 1H NMR were unsuccesful.Molecular mechanics and MNDO calculations satisfactorily reproduce the ground-state conformation.The calculated barrier for the enantiomerization process is 21.8 (MM2) and 28.2 (MNDO) kcal mol^-1. 2 was chromatographically resolved on a (+)-poly(triphenylmethyl)methacrylate (PTrMA) column.Its specific rotation is <α>²⁵ = -12100 deg at 365 nm and -2300 deg at 589 nm (D line).The activation parameters for the enantiomerization of 2 in perhydrofluorene are ΔG = ΔH = 39.6 kcal mol^-1 and ΔS = 0 cal mol^-1 K^-1.The barrier for 2 is the highest determined experimentally for a correlated rotation.