Evolution of propargyl ethers into allylgold cations in the cyclization of enynes

1,n-Enynes with propargyl alcohol, ether, or silyl ether units undergo gold(I)-catalyzed intramolecular 1,(n-1)-migration via allylgold cations (see scheme). These intermediates have been trapped by olefins, indole, and by a formal intramolecular C-H insertion. In the case of aryl-substituted 1,7-enynes, a cascade process involving a Nazarov-type cyclization leads to 6,7-dihydro-5H-benzo[c]fluorenes.