Gold(I)-Catalyzed Cycloisomerization–Dimerization Cascade of Benzene-Tethered 1,6-Enynes

An unprecedented stereoselective domino reaction of 1,6-enynes with an aryl ring at C3–C4 in the presence of gold­(I) catalysts at low temperature is described. This process involves a novel 5-exo-dig cycloisomerization–dimerization sequence to afford formal Diels–Alder adducts that undergo a smooth gold-catalyzed double bond migration at room temperature. In addition, the first examples of the gold mesoionic carbene mediated [2+2+2] cycloaddition of these enynes with benzaldehyde are reported.