Enhancement of double-bond participation in the solvolysis of 9-isopropylidene-endo-3,4-benzotricyclo[4,2,1,02,5]non-3-en-7-yl toluene-p-sulphonates by the effect of nonbonded interactions

Abstract

The rates and products of acetolysis of 9-isopropylidene-endo-3,4-benzotricyclo-[4,2,1,0^2,5]non-3-en-7-yl toluene-p-sulphonates (4b) and (6b) have been determined and compared with the analogous derivatives in the norbornyl- and endo-3,4-benzotricyclo[4,2,1,0^2,5]non-3-ene systems. An explanation based on the effect of nonbonded interactions on the reaction co-ordinate for the ionisation of (6b), has been advanced for the larger amount of double-bond participation found in the solvolysis of (6b) compared to that in the comparable norbornyl derivative (12). On the basis of product and rate studies of the solvolysis of (4b) a small contribution from participation of the C(5)–C(6) bond in the ionisation cannot be excluded.