Carboxylate‐Directed Oxidative Annulation via C(Alkenyl)－H Activation/Double Alkyne Insertion/1,4‐Pd Migration: Synthesis of Functionalized Naphthalenes

A palladium‐catalyzed double consecutive C(alkenyl)–H activation/alkyne insertion method utilizing a free carboxylic acid as a directing group in the preparation of functionalized naphthalenes is reported. The reaction mechanism involves a sequence of the C (alkenyl)−H activation/alkyne insertion/1,4‐palladium migration/reductive elimination steps. The second alkyne insertion occurred at the phenyl ring of the intermediate generated from the first alkyne insertion via 1,4‐palladium migration, which is an uncommon case in typical C–H activation/alkyne insertion chemistry, providing functionalized naphthalene products. Additionally, the kinetic studies and control experiments as well as density functional theory (DFT) studies are also investigated to elucidate the reaction mechanism.