Gold‐Catalyzed Cyclizations of Alkynyl Silyl Enol Ethers: An Easy Access to Bicyclo[3.2.1]octanone Derivatives

The efficient gold‐catalyzed cyclization reactions of alkynyl silyl enol ethers were successfully applied to the preparation of bicyclo[3.2.1]octanone derivatives. Accordingly, after optimization of the gold catalytic system, several bicyclic α,β‐unsaturated keto adducts were synthesized in good to excellent yields. The process followed a major 5‐ exo cyclization via an anti addition of the silyl enol ether to the π‐activated intermediate, which was demonstrated by a deuterium incorporation experiment. A 6‐ endo cyclization process was observed for a silyl enol ether bearing an electron‐donating aromatic group.