Stereoselective Synthesis of the Benzo­dihydro­pentalene Core of the Fijiolides

An efficient stereoselective synthesis of the enantiomer of the benzo­dihydro­pentalene core of fijiolides A and B has been achieved. The asymmetric conjugate addition of styrylboronic acid to an indenone produced the first stereocenter. Ring C was installed by ring-closing metathesis of a <i>cis</i> disubstituted indanone. Regioselective epoxide opening by NaSePh and subsequent oxidative elimination produced an allylic alcohol. The final introduction of the cyclopentadiene was possible by elimination of an <i>in situ</i> formed triflate.