Tris(benzocyclobutadieno)triphenylene and Its Lower Biphenylene Homologues by Palladium-Catalyzed Cyclizations of 2,3-Didehydrobiphenylene

<UFIGR ID="ol048548on00001">The Pd-catalyzed cycloaddition of didehydrobiphenylenes <BO>2a</BO>,<BO>b</BO>, generated from the corresponding 3-(trimethylsilyl)-2-biphenylenyl triflates with fluoride, furnishes the C<INF>3</INF>-symmetric trimers <BO>1a</BO>,<BO>b</BO> in which the embedded triphenylene unit is distorted to increase the aromaticity of the central benzene ring. Cocylization of <BO>2a</BO>,<BO>b</BO> with dimethyl acetylenedicarboxylate provides the phenanthrene- and naphthalenecarboxylic ester analogues, depending on the catalyst used.