Gold-catalyzed direct cycloketalization of acetonide-tethered alkynes in the presence of water

A methodology for the direct preparation of bridged acetals from acetonide-tethered alkynes under gold catalysis in the presence of water has been developed. The bicyclic ring structures bearing a bridged five-membered ring arise from the regioselective bis-oxycyclization by initial attack of the oxygen atom to the internal alkyne carbon.