Tandem bicycle: A gold‐catalyzed geminal carbo‐functionalization reaction of 3‐siloxy‐1,3‐dien‐8‐ynes proceeded smoothly to give bicyclo[4.3.0]nonanes stereoselectively through ring expansion of the bicyclic carbene complex intermediates. The product configuration was different from that of the thermal Diels–Alder adduct.
Tungsten(0)‐ and rhenium(I)‐catalyzed reactions of acetylenic dienolsilylethers based on the concept of geminal carbo‐functionalization of alkynes are reported. Treatment of 3‐siloxy‐1,3‐diene‐7‐ynes with catalytic amounts of [W(CO)6] or [ReCl(CO)5] under photoirradiation conditions gives synthetically useful bicyclo[3.3.0]octane derivatives in good yields. Extremely high catalytic activity is noted