The interrupted Pummerer reaction in a sulfoxide‐catalyzed oxidative coupling of 2‐naphthols

A benzothiophene S‐oxide catalyst, generated in situ by sulfur oxidation with H2O2, mediates the oxidative coupling of 2‐naphthols. Key to the catalytic process is the capture and inversion of reactivity of a 2‐naphthol partner, using an interrupted Pummerer reaction of an unusual benzothiophene S‐oxide, followed by subsequent coupling with a second partner. The new catalytic manifold has been showcased in the synthesis of the bioactive natural products, (±)‐nigerone and (±)‐isonigerone. Although Pummerer reactions are used widely, their application in catalysis is rare, and our approach represents a new catalytic manifold for metal‐free C−C bond formation.