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 H2O and alkanols (see scheme). The highly efficient AuCl3-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.