The camphenehydro (methylcamphenilyl) and isobornyl (bornyl) cations. I. Generation of the enantiomeric cations by the p- and s-routes of solvolysis.

The acetolysis of α-campholenyl [2-(2',3',3'-trimethylcyclopent-3'-enyl)] p-nitrobenzenesulphonate proceeds with π-bond participation to give cyclized products (99.7%) derived from the equilibrating classical camphene hydro and isopropyl cations. The composition of the product is similar, but not identical, to those formed by the σ-route from the acetolysis of suitable isopropyl and bornyl derivatives. When α-campholenyl p-nitrobenzenesulphonate and the isopropyl derivatives are prepared from (+)-camphor, the two enantiomers of camphene having high optical purities are formed. A simple procedure for the preparation of camphene of high optical purity from isoborneol is described.