Sulfuric acid catalyzed rearrangements of 1- and 3-homoadamantanols

4-Homoadamantyl cation. III. Sulfuric acid catalyzed rearrangement of 4-homoadamantanol-5-13C

“…Dihedral angles between Scheme IV 10 -18.77°a Calculated heats of formation (kcal/mol) of the corresponding hydrocarbons.13 the 2-homoadamantyl cation empty p orbital and the migrating C-C bonds are similar in all four cases (20-40°). However, the calculated heats of formation (as well as strain energies) of the hydrocarbons corresponding to cations 8, 9, 10, and 11 are significantly different.13 Since all four cations (8)(9)(10)(11) are secondary, the relative stabilities of these cations should roughly parallel to the relative stabilities of the corresponding hydrocarbons. Cation 8 appears to be the most stable, whereas cations 9 and 10 are considera- bly less stable.…”

“…Using the same approach it can be predicted that rearrangement pathways b and c of the 2-homoadamantyl cation probably cannot compete successfully with pathways a and d (see Scheme IV). A reasonable mechanism of the conversion of the 4-homoadamantyl cation to 4-homoisotwistane via 8 is outlined in Scheme V. However, cation 11 is only about 2 kcal/mol less stable than cation 8 and cannot be excluded as a possible intermediate in the conversion of the 4-homoadamantyl cation to 4-homoisotwistane. There are a number of possible pathways for this conversion via cation 11 several of which involve only cationic intermediates with stabilities comparable to that of 8 and 11.…”