Acetolysis of exo- and endo-bicyclo[3.3.1]nonan-3-yl toluenesulphonates

Abstract

The rate constants for buffered acetolysis at 25° of exo- and endo-bicyclo[3.3.1]nonan-3-yl toluenesulphonates (2a and b) have been found to be 5.78 × 10^–5 and 5.96 × 10^–4 s^–1, respectively. The value found for (2b) differs from that given in an earlier report. Activation parameters are reported. The major product in both cases is bicyclo[3.3.1]non-2-ene. The bicyclo[3.3.1]nonan-3-yl acetate formed in the acetolysis of (2a) shows excess of retained stereochemistry. By use of a deuterium-labelled substrate the total amount of 3,7-hydride shift occurring in the reaction of (2a) has been found to be 5.9%, with the largest proportion of rearrangement (20.8%) appearing in the acetate of retained configuration. Empirical force field calculations on exo- and endo-bicyclo[3.3.1]nonan-3-ols (3a and b) and on the bicyclo[3.3.1]nonan-3-yl cation have been used to elucidate a possible course of reaction.