Intramolecular [4 + 2] Cycloadditions of 1,3-Enynes or Arylalkynes with Alkenes with Highly Reactive Cationic Phosphine Au(I) Complexes

New Au(I) complexes with bulky, biphenyl phosphines are the most reactive catalysts for the cyclizations of enynes. 1,6-Enynes with an aryl ring at the alkyne give 2,3,9,9a-tetrahydro-1H-cyclopenta[b]naphthalenes by a 5-exo-dig cyclization followed by a Nazarov-type ring expansion. 1,8-Dien-3-ynes also cyclize by a 5-exo-dig pathway to form hydrindanes.