Oxonium allyl ether rearrangements

Allylic alcohols, esters, and ethers undergo acid-catalyzed isomerizations, and allylic alcohols and ethers isomerize at appreciable rates only in the presence of acids. The migrating groups in these reactions are uncharged molecules derived from the oxonium ion conjugate acids of the starting materials. For this reason, and because they are mechanistically related to anionotropic isomerizations, Braude named these reactions oxotropic rearrangements. 

Gold-catalysed ring closure of 1,5-enyne eontaining a silyl ether at the allylic position has been reported to induce a skeletal rearrangement to form an oxonium intermediate, which undergoes intra- and inter-molecular allylation (Scheme 119). ... 

---