Gold-Catalyzed Formation of Oxonium Ions from Enynes and Their Intra- and Intermolecular Trapping with Allylsilanes

Gold-catalyzed ring closure of 1,5-enyne containing a silyl ether at the allylic position induces a skeletal rearrangement to form an oxonium intermediate, which then undergoes a smooth allylation in both an intra- and intermolecular manner. In the intramolecular allyl transfer, the additive alcohol becomes positioned on the silicon of the silyl ether by forming a new Si–OR bond, whereas, in the intermolecular allylation, the alcohol is incorporated in the homoallylic carbon by forming a C–OR bond.