Highly efficient access to bi- and tricyclic ketals through gold-catalyzed tandem reactions of 4-acyl-1,6-diynes.

Single step: Fused bicyclic and bridged tricyclic ketals were synthesized in a single step from the reactions of easily available 4-acyl-1,6-diynes with H(2)O and alkanols (see scheme). The highly efficient AuCl(3)-catalyzed multicomponent domino reactions, involving five C-O bond formations, can proceed in a highly regio- and diastereoselective manner at room temperature under air and lead to structures of high molecular complexity from simple starting materials in an atom economic way.