HNTf₂‑Catalyzed Regioselective Preparation of Polysubstituted Naphthalene Derivatives Through Alkyne–Aldehyde Coupling

We report herein the preparation of polysubstituted naphthalene derivatives by the original Brønsted-acid-catalyzed benzannulation reaction of phenylacetaldehydes with alkynes. This reaction, which was usually performed with Lewis acids under thermal activation, is efficiently promoted by 15 mol % of triflimide (HNTf₂) at room temperature under metal-free and mild reaction conditions and leads with a perfect regioselectivity to a wide variety of diversely functionalized naphthalenes in 41–78% yield. A catalytic cycle is proposed together with some further applications of this catalytic system in the related benzannulation transformations of epoxide and acetal derivatives