2.5- Dehydro-4-protoadamantyl cations

Olah and coworkers NMR study of the 8,9-dehydro-2-adamantyl cation, obtained from the corresponding alcohol in superacidic medium, showed the equivalence of C2, C8 and C9 carbons ((5 C 157.0) in agreement with the conclusions of solvolytic studies Even at -120 °C the structure of the cation could not be frozen out to a static cation, showing the extremely fast equilibration of the threefold degenerate cyclopropylcarbinyl cation 74. An identical NMR spectrum was obtained from the ionization of the 2,5-dehydro-4-protoadamantanol, which prompted the suggestion of the intermediacy of the 2,5-dehydro-4-protoadamantyl cation 75. The ion rearranges to an ally lie cation 76 at -78 (equation 45). 

Two different dimethyl-8,9-dehydroadamantyl cations have also been investigated by Olah and coworkers. The 1,2-dimethyl-8,9-dehydroadamantyl cation [141] prepared by Olah et al. (1978b) was found to be a static cyclo-propylcarbinyl cation from —95°C to —10°C. No contribution from the 2,5-dehydro-4-protoadamantyl cation [142], and no degenerate rearrangement was observed for [141]. The other isomer, the 2,8-dimethyl-8,9-dehydro-... 

---