2-Norbornyl cations with spiroannellated cyclobutane rings clobutane] (29, 33, 34). In both series, ring expansion of the spiroannellated cyclobutane, by exo-3,2-C shift, was the were generated for comparison with the previously studied cyclopropane analogues. Starting with the Diels-Alder reac-major reaction, giving rise to a uniquely endo-selective tertiary cation (36). Analogously positioned cyclopropane rings tion of cyclopentadiene with methylenecyclobutane, spiro-[bicyclo[2.2.1]heptane-2,1Π-cyclobutan]-6-one (11) was pre-remain intact, due to stabilizing interactions with the neighboring positive charge which are lacking in the cyclobutane pared. The tosylhydrazone 12 of 11 was photolyzed in NaOD/D 2 O to give the analogous alcohol 13 with a ca. 1:1 systems. Οͺ In CDCl 3 solution, the tosylate 32 produced mixtures of isomeric tosylates by way of ion pair recombination. distribution of deuterium. Ring expansion was not observed, in contrast to the cyclopropane analogue. Οͺ The tosylhydra-We observed that exo Η exo shifts of the counterion proceed with little scrambling of 18 O whereas complete equilibration zone 22 of spiro[bicyclo[2.2.1]heptane-2,1Π-cyclobutan]-3one (21) and the related tosylates (28, 32) rearranged, in part, of the tosylate oxygens is attained in exo Η endo shifts. to afford derivatives of spiro[bicyclo[2.2.1]heptane-7,1Π-cy-