Tf₂NH-Mediated Twofold Aromatization Reaction of Dimers of Ethynylcyclopropanes to Bibenzoisocoumarins

Tf₂NH-mediated twofold aromatization reaction of dimeric ethynyl-substituted cyclopropanes followed by lactonization has been developed for facile synthesis of bibenzo[f]isocourmarin derivatives in moderate to good yields. In particular, with respect to the electron-rich phenyl ring for intramolecular hydroarylation with alkynes, a single or double direct ring-opening aromatization reaction occurred to produce the isomeric benzo[h]isocoumarin moiety. Preliminary photophysical properties of these bibenzoisocoumarin isomers are provided as well.