Ring-Closing Metathesis with Vicinal Dibromoalkenesas Protected Alkynes: A Synthetic Approach to Macrocyclic Enynes.

A new strategy toaccess macrocyclic enynes was developed. To blockundesired ene–yne cyclization pathways, alkynes were protectedvia bromination and the resultant acyclic vic-(E)-dibromotrienes participated in selective ene–enering closing metathesis reactions. Zinc-promoted deprotection of (E)-dibromodienes provided macrocyclic enynes in high yields. [ABSTRACT FROM AUTHOR]