Gold-catalyzed cycloisomerization of siloxy enynes to cyclohexadienes.

We have described the first Au-catalyzed cycloisomerization of 1-siloxy-5-en-1-ynes. The reaction is efficiently catalyzed by AuCl (1 mol %) to afford siloxy cyclohexadienes, which can be readily converted to the corresponding 1,2- and 1,3-cyclohexenones. The catalytic process displays a broad substrate scope and exceedingly mild reaction conditions (30 min, 20 degrees C). The presence of a siloxy alkyne moiety is crucial for enabling the skeletal reorganization process, which is postulated to proceed via a novel reaction mechanism involving a cascade of 1,2-alkyl migrations.