Palladium‐Catalyzed Intermolecular [4+1] Spiroannulation by C(sp 3 )−H Activation and Naphthol Dearomatization

A novel palladium‐catalyzed [4+1] spiroannulation was developed by using a C(sp 3 )−H activation/naphthol dearomatization approach. This bimolecular domino reaction of two aryl halides was realized through a sequence of cyclometallation‐facilitated C(sp 3 )−H activation, biaryl cross‐coupling, and naphthol dearomatization, thus rendering the rapid assembly of a new class of spirocyclic molecules in good yields with broad functional‐group tolerance. Preliminary mechanistic studies indicate that C−H cleavage is likely involved in the rate‐determining step, and a five‐membered palladacycle was identified as the key intermediate for the intermolecular coupling.