Active Pd species in the formation of polysubstituted olefins and naphthalenes in the reaction between arylboronic acid and diphenylacetylene

‘Ligand-free’ Pd-catalyzed reaction between arylboronic acid and diphenylacetylene affords a set of polyphenylated olefins and 1,2,3,4-tetraphenylnaphthalene whose yields are dependent on counteranion of Pd^II salt and additive nature. Tetraphenylethylene and hexaphenylbuta-1,3-diene are likely formed in tandem arylation/cross-coupling reaction with the participation of hydroxo/alkoxo alkenyl Pd species, whereas 1,2,3,4-tetraphenylnaphthalene formation probably proceeds through tandem arylation/C–H activation by halide-containing alkenyl Pd complexes.