13C Chemical Shifts of Highly Substituted Bicyclo[2.2.1]heptanes

Abstract

The 13C chemical shifts have been determined for a series of highly substituted norbornanes. A comparison of the observed values with the expected chemical shifts, determined as described by Lippmaa, establishes that 13C shifts may be predicted reasonably accurately even in highly substituted norbornyl systems. Since substituted norbornanes definitely exist in synchro or contra twist forms as shown by Altona, the results show that Lippmaa's substituted shift parameters must already account for the major part of the increments that arise via hybridization changes resulting from the distortion of the [2.2.1]-skeleton.