Tandem Ruthenium-Catalyzed Transfer-Hydrogenative Cyclization/Intramolecular Diels–Alder Reaction of Enediynes Affording Dihydrocoumarin-Fused Polycycles

A tandem transfer-hydrogenative cyclization/intramolecular Diels-Alder reaction of enediyne substrates, containing 1,6-diyne, acrylate dienophile, and phenol tether moieties, was successfully accomplished using the combination of a cationic ruthenium complex, [CpRu(AN)3]PF6 (1b, Cp = η(5)-C5H5, AN = MeCN), as the catalyst and a Hantzsch ester as the H2 surrogate to afford interesting dihydrocoumarin-fused polycyclic products as single diastereomers.