Stereoselective Synthesis of Tricyclic Pyranoxepin Derivatives by Ruthenium-Catalyzed Enyne Metathesis/Diels-Alder Reaction

Synthesis of tricyclic oxepin-annulated pyrone derivatives has been achieved by the ring-closing enyne metathesis using the firstgeneration Grubbs’ catalyst under a nitrogen atmosphere. The Diels-Alder reaction of these cyclized products with the dienophile proceeded smoothly to afford the tricyclic compounds in ­excellent yield.