Thermal and Au(I)-Catalyzed Intramolecular [4+2] Cycloaddition of Aryl-Substituted 1,6-Diynes for the Synthesis of Biaryl Compounds

1,6-Diynes, possessing aryl groups on their termini, undergo an intramolecular [4+2] cycloaddition via strained cyclic allene intermediates to give various biaryl compounds. Under thermal conditions, isomerization of the intermediates occurs, while, in the presence of a cationic gold catalyst, skeletal rearrangement is a ­major pathway.