Bicycloheptyl, Bicyclohexyl, and Bicyclooctyl Cations

4 Bicycloheptyl, Bicyclohexyl, and Bicyclooctyl Cations 4.1 Hie fficyclo/2,2,l/hexyI Cation 

It is interesting to compare the 2-norbornyl cation with its lower homologue — the 2-bicyclo[2,l,l]hexyl cation. Calculations with the MINDO/3 method show that the steric strain in the bicyclo[2,l,l]hexyl ion makes it a particularly favourable model for exhibitingCT-participation 

Meinwald et al. ) assumed from kinetic and stereochemical data that the solvolysis of the 2-endo-tosyloxy-bicyclo[2,l,l]hexane 142 yields an intermediate nonclassical ion 143  

The CNDO calculations show that the activation energy for this rearrangement must be very low . At the same time the nonclassical ions can be expected to permit but a low rate of hydrogen migration from the methylene group to the cation centre. 

It is of interest to compare the chemical shifts in the PMR spectra of the 2-norbomyl 5 and the 2-bicyclo[2,l,l]hexyl 143 cations. While the bridge-head protons 

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