Coupling and Decoupling Approach Enables Palladium-Catalyzed Aerobic Bimolecular Carbocyclizations of Enediynes to 2,6-Diacylnaphthalenes

A formal palladium-catalyzed aerobic bimolecular carbocyclization reaction of (Z)-hexa-1,5-diyn-3-ene scaffolds has been successfully developed for the construction of 2,6-diacylnaphthalenes, wherein copper salts play a critical role in accomplishing the oxygenative homo- and heterodimerization processes of readily accessible enediyne-carboxylic acids and esters, respectively. The enediyne dimerization protocol provides a flexible and regiospecific approach to a variety of functionalized naphthalenes with up to six differentiated substituents in good yields by using a directing-group-assisted coupling and decoupling strategy. Mechanistic studies indicated that the two oxygen atoms being selectively incorporated into the crossover-annulation products of enediynecarboxylic acid and ester directly originate from atmospheric molecular oxygen and H2O, respectively.