Heteroannulation of bicyclobutane derivatives via Au-catalyzed hydration to enol ethers and intramolecular cyclization giving spirocyclobutanes

We report the heteroannulations of bicyclobutane derivatives bearing enol ether groups in the presence of H2O under mild conditions. The reaction affords spirocyclobutanes with cyclic acetal groups via the Au-catalyzed hydration of the enol ether group and subsequent intramolecular cyclization.