Nucleophilic carbon-carbon bond formation by 1-En-3-ynes via zirconocene-η2-1-en-3-yne complexes

Abstract

Nucleophilic reactions by the C1 atom of 1-en-3-ynes toward organic electrophiles such as ketones, nitriles and isocyanates, via their organozirconium species, were investigated.Zirconocene complexes of conjugated 1-en-3-ynes coordinating in a η2-fashion were prepared, and then reacted with ketones, nitriles and isocyanates to afford seven-membered intermediate organozirconium compounds via CC bond formation. The corresponding alcohols, ketones, pyrroles and amides were obtained after hydrolysis. The products were, in principle, the same as those obtained from five-membered zirconacycloallene complexes, which were prepared from low-valent zirconocene and 1-en-3-ynes in the absence of ancillary ligands. Because only a limited number of 1-en-3-ynes can form zirconacycloallenes in significant yields, the present study allows a wider scope of 1-en-3-ynes for this synthetically useful reaction.