An adamantane rearrangement. A new pathway

Tricyclo(4.2.2.o^1,5)decane ($\text{7}$) in the presence of AlBr₃ rearranges partly “forwards” to adamantane ($\text{1}$) and partly “backwards” to tetrahydrodicyclopentadiene ($\text{2}$, largely the oxo isomer). Intermediate $\text{14}$, characterizing the $\text{7}$→exo-$\text{8}$→$\text{14}$→$\text{3}$→$\text{1}$ forward pathway, is found only in small amounts. The detection of a new intermediate, $\text{12}$, also shows that a second major rearrangement route from $\text{7}$ to $\text{1}$ is being utilized (see dashed lines in Figure 1).