Visible-Light-Catalyzed Synthesis of α-Naphthol Derivatives via a Radical Cascade Reaction of Phosphorus Ylides.

α-Naphthol constitutes the core scaffold of numerous anti-inflammatory and antitumor bioactive molecules, while conventional synthetic approaches suffer from harsh reaction conditions. Herein, a visible-light-catalyzed radical cascade cyclization is developed for the efficient assembly of α-naphthol derivatives using readily available phosphorus ylides and alkynes. With 4DPAIPN or fac-Ir(ppy)3 as the photocatalyst and HBF4 as the additive, this transformation proceeds under blue light at room temperature without additional oxidants or strong bases. The reaction exhibits broad substrate compatibility with various substituted aromatic rings, alkyl groups, and drug-derived alkynes. Mechanistic experiments confirm a radical pathway: phosphorus ylides react with HBF4 to form quaternary phosphonium salts in situ, which generate active radicals via single-electron transfer. Subsequent cyclization, oxidation, and deprotonation deliver target products, offering a mild and practical strategy for synthesizing α-naphthols.