W(CO)5-amine catalyzed exo- and endo-selective cyclizations of omega-alkynyl silyl enol ethers: a highly useful method for the construction of polycyclic compounds.

[reaction: see text] A highly useful method for the construction of polycyclic compounds based on the amine-controlled exo- and endo-selective cyclizations of omega-alkynyl silyl enol ethers catalyzed by W(CO)5L is reported. When bis-alkynyl silyl enol ethers were treated with a catalytic amount of W(CO)6, DABCO, and water under photoirradiation, synthetically useful tricyclic ketones were obtained in good yield.