Efficient Control of π-Alkyne and Vinylidene Complex Pathways for the W(CO)₅(L)-Catalyzed Synthesis of Two Types of Nitrogen-Containing Bicyclic Compounds

When ω-acetylenic dienol silyl ethers containing NMs part in the tether were treated with a catalytic amount of W(CO)6 under photoirradiation, 2-azabicyclo[3.3.0]octanes were obtained in good yield via π-alkyne complexes. On the other hand, treatment of the same substrates with a catalytic amount of W(CO)6 in the presence of n-Bu3N under the same reaction conditions gave 3-azabicyclo[3.3.0]octanes in good yield exclusively via vinylidene complexes. Thus, the π-alkyne and vinylidene complex pathways are easily controlled by using a catalytic amount of W(CO)5(L) and an amine.