Sequential cyclization/silylation of dienynes catalyzed by an organoyttrium complex

The organoyttrium complex Cp*2YCH3. THF (Cp* = C5Me5) has been shown to be an effective precatalyst for the selective sequential cyclization/silylation of dienynes. The catalyst's ability to insert the alkyne in preference to the alkenes in a regioselective manner, combined with the high diastereoselectivity of the intramolecular insertion process, leads to bicyclo[3.3.0]octane products in high yield. The stereochemistry of the exocyclic olefin, the ring fusion, and the ring substituents are all controlled in the reaction. The cyclization of dienynes thus affords silylated carbobicyclics with high diastereoselectivities in excellent yields.