Coupling and Decoupling
Approach Enables Palladium-Catalyzed
Aerobic Bimolecular Carbocyclizations of Enediynes to 2,6-Diacylnaphthalenes
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Abstract
A formal
palladium-catalyzed aerobic bimolecular carbocyclization
reaction of (<i>Z</i>)-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 hetero-dimerization 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 H<sub>2</sub>O, respectively