Tandem Ring Expansion of Alkenyl Benzocyclobutenol Derivatives into Substituted Naphthols

Abstract

Twice expanded: Substituted naphthols were prepared in a novel synthetic route starting from alkenyl benzocyclobutenol derivatives. The conversion includes two successive ring-enlargement processes (A→B→C; see scheme). The halonium ion (X+) induces expansion of the four-membered ring to a five-membered ring, and SmI2 promotes the expansion of the five-membered ring to the six-membered ring with concomitant elimination of ROSmI2.