Montmorillonite K-10-catalyzed intramolecular rearrangement of vinylidenecyclopropanes

A series of naphthalene, indene, and 6aH-benzo[c]fluorene derivatives are synthesized by intramolecular rearrangement of vinylidenecyclopropanes using a heterogeneous solid acid catalyst, montmorillonite K-10, under mild reaction conditions in good to excellent yields. The solid acidic catalyst, montmorillonite K-10, can be recovered and reused.