Ring-Opening/Expansion Rearrangement of Cycloprop[2,3]inden-1-ols Catalyzed by p-Toluenesulfonic Acid

A divergent approach to generate either 1-hydroxymethylindenes (which could then be converted to benzofulvenes through a dehydration reaction) or naphthalenes by the rearrangement of cycloprop[2,3]inden-1-ols is reported. The effect of the cyclopropyl ring substitution pattern on ring-opening/expansion rearrangements of the substrates was systemically studied.