Medium-Sized Cyclophanes. VI. High-Temperature NMR Spectra of [2.2]Metacyclophane and Optical Resolution of 4,14-Disubstituted Derivatives

The NMR spectra of [2.2]metacyclophane have been shown to be held unchanged over a wide range of temperature, ca. −80 to 190°C, indicating that the ten-membered ring system undergoes no inversion and is frozen in a chair conformation. It may, then, be expected that suitably substituted derivatives of [2.2]metacyclophane would become disymmetric due to restricted inversion; such was proved to be the case by carrying out the optical resolution of the 4, 14-di-substituted derivatives. The 4,14-dimethyl derivative was resolved by means of a complex formation with Newman’s reagent, [α]57826=−3.4 and +4.2°. 4,14-Dicarboxylic acid was also resolved by converting it to the quinine salt, [α]d22=+5.0°.