A study of methyl-substituted 2-Arylbicyclo[2,2,1]hept-2-yl cations

Abstract

The ¹³C and ¹H N.M.R. spectra of a series of 2-aryl-1,7,7- trimethylbicyclo[2,2,1]hept-2-yl cations generated in strong acid at low temperature are reported. These cations reorganize at higher temperatures to 2-aryl-5,5,endo-6-trimethylbicyclo[2,2,1]hept-2-yl cations, thereby relieving the unfavourable C 1 methyl-C 2 aryl steric interaction present in the parent cations. At higher temperatures the bicyclic skeletons collapse to monocyclic allylic cations.