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 H 2 O 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.