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

摘要

Enynes I cyclize by a 5-exo-dig pathway with electrophilic transition metal complexes or halides MX_n as catalysts to give a variety of cycloisomerization and addition derivatives via metal cyclopropyl carbenes II as intermediates (Scheme I).Thus,reaction with nucleophiles R'OH (alcohols or water) gives products of type III,whereas in the absence of nucleophiles,dienes IV by skeletal rearrangement or,less commonly,cyclobutenes V can be obtained.