The EtAlCl2-mediated intramolecular addition of silyl enol ethers to both terminal and internal unactivatedalkynes, bearing alkyl and phenyl susbstituents at the alkyne moiety, proceeded exclusively in the endo-fashion to give mono- and bicyclic β,γ-unsaturated ketones in good to excellent yields. The mechanism of this regiospecific Lewis acid-assisted carbocyclization is proposed.
The EtAlCl2-mediated intramolecular addition of silyl enol ethers to both terminal and internal unactivatedalkynes, bearing alkyl and phenyl susbstituents at the alkyne moiety, gave mono- and bicyclic β,γ-unsaturated ketones in good to excellent yields. On the other hand, the silyloxy-substituted cyclic vinylsilanes were obtained in moderate to high yields when the reactions were catalyzed by B(C6F5)3