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Synthesis of 1,4-naphthoquinone methides via acid-catalyzed cascade cyclizations of benzannulated enediynyl alcohols.

Treatment of benzannulated enediynyl alcohols with trifluoroacetic acid at room temperature promoted a cascade sequence of cyclization reactions, leading to 1,4-naphthoquinone methides. The transformation involved an unusual two-carbon ring expansion from the cyclic alcohols and the construction of the p-quinone methide ring from an acyclic system along the reaction pathway.