Ruthenium-catalyzed intramolecular homo-diels-alder reaction of alkyne-tethered norbornadienes. An entry to fused angular triquinanes.

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.