Palladium-catalyzed formation of highly substituted Naphthalenes from arene and alkyne hydrocarbons

Several highly substituted naphthalenes 3 have been synthesized in a one-pot reaction by treatment of arenes 1 with alkynes 2 in the presence of palladium acetate and silver acetate. In this Pd-catalyzed protocol, an arene provides a benzo source for the construction of a naphthalene core through twofold aryl C-H bond activation. Reaction of triphenylphosphine with diphenylethyne (2a) under the catalysis of Pd-IV complexes produced 1,2,3,4-tetraphenylnaphthalene (3ba) in 62% yield. Here, triphenylphosphine undergoes one aryl C-P bond cleavage and one aryl C-H bond activation to serve as a benzo moiety. Crystal structures of cycloadducts 3ea, 3ga, and 3ac have been analyzed. The twisted naphthalenes arise not only from the overcrowded substituents but also from the contribution of the CH3-pi interaction.