Palladium-Catalyzed Four-MemberedRing Annelation Reactions at Dibenzobarrelene

A palladium-catalyzed coupling process of dibenzobarrelene withannelated aryl halides leads to special benzocyclobutenes, resemblingDiels-Alder adducts of antiaromatic benzocyclobutadieneswith anthracene. Moderate steric pressure in intermediary five-memberedpalladacycles seems to be decisive for this type of transformation.