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

[GRAPHICS] 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)(5)(L) 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.