Brønsted Acid-Catalyzed Intramolecular Tandem Double Cyclization of γ‑Hydroxy Acetylenic Ketones with Alkynes into Naphtho[1,2‑b]furan-3-ones

A metal-free and atom-economic route for the synthesis of naphtho­[1,2-b]­furan-3-ones has been realized via p-TsOH·H2O-catalyzed intramolecular tandem double cyclization of γ-hydroxy acetylenic ketones with alkynes in formic acid. The benzene-linked furanonyl-ynes are the key intermediates obtained by the scission/recombination of C–O double bonds. Further, the structural modifications of the representative product were implemented by reduction, demethylation, substitution, and [5 + 2]-cycloaddition.