Ruthenium-Catalyzed Intramolecular Homo-Diels−Alder Reaction of Alkyne-Tethered Norbornadienes. An Entry to Fused Angular Triquinanes
摘要:
2-(Pent-4-ynyl)norbornadienes undergo an intramolecular [2 + 2 + 2] cycloaddition in the presence of (nbd)RuCl2(PPh3)(2) as a catalyst affording annelated deltacyclenes in good to excellent yields. The usefulness of the reaction is illustrated by the straighforward conversion of pentacyclene 2a into the angularly fused triquinane 19.