Acetolysis of endo-5-Methyltricyclo-[2,2,1,02,6]hept-exo-3-yl and endo-5-Methyltricyclo[2,2,1,02,6]hept-endo-3-yl p-Bromobenzenesulfonates

Abstract

Acetolyses of the title compounds (4b) and (5b) at 25�7� proceed with steady first-order kinetics and with comparable rate constants. Some isomerization of (5b) to (4b) occurred during acetolysis of (5b). The products derived from acetolysis of each p-bromobenzenesulfonate were comparable and included endo-5-methyltricycl0[2,2,1,02,6]hept-exo-3-yl acetate (4c), endo-5-methyltricyclo- [2,2,1,02,6]hept-endo-3-yl acetate (5c), endo-3-methylbicyclo[2,2,1]hept-5-en-exo-2-yl acetate (6) and anti-7-methylbicyclo[2,2,1]hept-5-en-exo-2-yl acetate (7). These results are rationalized in terms of a reaction mechanism involving isomerization of the endo to the exo intimate ion pair, (10) to (ll), as well as a capturable intermediate carbocation which is common to the acetolysis of both p-bromo- benzenesulfonates.