Lewis Acid Catalyzed Cascade Reaction to Carbazoles and Naphthalenes via Dehydrative [3 + 3]-Annulation

A novel Lewis acid catalyzed dehydrative
[3 + 3]-annulation of
readily available benzylic alcohols and propargylic alcohols was developed
to give polysubstituted carbazoles and naphthalenes in moderate to
good yields with water as the only byproduct. The reaction was presumed
to proceed via a cascade process involving Friedel–Crafts-type
allenylation, 1,5-hydride shift, 6π-eletrocyclization, and Wagner–Meerwein
rearrangement.