A study of cations generated from 1-Methyl- and 7,7-Dimethyl-2-phenylbicyclo-[2,2,1]heptan-2-ols

Abstract

Attempts to generate the 1-methyl-2-phenylbicyclo[2,2,1]hept-2-yl cation (6) by reaction of 1-methyl-exo-2-phenylbicyclo[2,2,1]heptan- endo-2-ol (5) with HSO₃F in SO₂ClF were not successful, due to spontaneous rearrangement to endo-6-methyl-2-phenylbicyclo[2,2,1]hept- 2-yl cation (7). This cation (7) itself rearranges at higher temperatures to exo-6-methyl-2-phenylbicyclo[2,2,1]hept-2-yl cation (10) probably by a double Wagner-Meerwein rearrangement involving the intermediacy of 3-methyl-1-phenylbicyclo[3,1,1]hept-2-yl cation (11). The 7,7-dimethyl-2-phenylbicyclo[2,2,1]hept 2-yl cation (13) has been generated and shown to rearrange to 5,5-dimethyl-2- phenylbicyclo[2,2,1]-hept-2-yl cation (14). At higher temperature, the bicyclic skeleton collapses to 3-isopropyl-1-phenyl-cyclohex-2-en-1-yl cation (15). These results demonstrate the structural requirements for cleavage of the 1,7-bond in the bicyclo[2,2,1]heptane skeleton.