Aromatic enynes can be transformed into arylnaphthalenes or benzofulvenes depending on the reaction conditions. Under gold(I) catalysis, exclusive or major 6‐endo‐dig cyclization took place leading to arylnaphthalenes. However, a catalytic system based on palladium iodide/1,3‐bis(diphenylphosphino)propane, in the presence of cesium carbonate as a base was necessary to furnish exclusively 5‐exo‐dig cyclization pattern, regardless of the electronic effects of the substituents. In the latter transformation, a mechanistic study (kinetic isotopic effect, density functional theory) involving a CH activation is suggested for the exclusive formation of benzofulvenes. magnified image
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Aziz et al. (2013) studied this question.