Sequential cyclization/silylation of enynes 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 1,6- and 1,7-enynes.. The catalyst's ability to insert the alkyne in preference to the alkene in a regioselective manner, combined with the high diastereoselectivity of the insertion process, yields a product with only one stereochemistry about the exocyclic olefin. The reaction proceeds under extremely mild conditions with short reaction times. Cyclization of enynes functionalized in the allylic position affords silylated carbocycles with high diastereoselectivities and excellent yields.