Preparation of [4]- and [5]Ferrocenophanes by Ruthenium-Catalyzed Ring-Closing Ene−Yne Metathesis

Transannular ring-closing ene−yne metathesis of 1-(ω-alkenyl)-1′-propargylferrocene derivatives affords the corresponding ferrocenophanes in good yields in the presence of the second-generation Grubbs Ru catalyst. The reaction is applicable to the preparation of [4]- and [5]ferrocenophanes. The ferrocenophanes obtained by the present reaction possess a conjugated diene functionality in the bridging side chain, and their further modification is attained via Diels−Alder cycloaddition with tetracyanoethylene or dimethyl acetylenedicarboxylate in a highly diastereoselective fashion.