Ring‐Closing Metathesis of Ene‐Ynamide: Application to the Synthesis of Medium‐Sized Cyclic Dienamide

Summary: Ring‐closing metathesis (RCM) of ene‐ynamide, which could be applied to the synthesis of various heterocycles containing 7‐ and 8‐membered rings, was investigated. Ene‐ynamides are easily synthesized by the known method. When a toluene solution of ene‐ynamide was stirred in the presence of a catalytic amount of second‐generation ruthenium carbene complex 1 under an ethylene atmosphere, RCM proceeded smoothly to provide a heterocyclic compound having a diene moiety in good to high yield. A substituent of the ynamide moiety affected the yield of the cyclized product.