Acid-Catalyzed Skeletal Rearrangement of Epoxy Alkynes: A Fast Access to Highly Functionalized Allenes

The acid-catalyzed reaction of epoxy alkyne involves an epoxide ring-opening attacked by π-alkyne, leading to a semipinacol-type rearrangement. In this process, a type of carbon−carbon 3,3-migration of the alkyne system has been discovered, which is promoted both by epoxide inducing and hydroxide promoting. This transformation enables the fast synthesis of allenes in mild conditions.