Palladium-catalyzed Annulation of 2-Substituted Silylethynyloxybiaryls through δ-C-H Activation

The intramolecular hydroarylation of 2-(silylethynyloxy)-biphenyls takes place with the aid of a palladium catalyst to give 6-methylene-6H-dibenzo[b,d]pyrans. The product can be transformed into 6,6-disubstituted dibenzopyrans via protodesilylation, followed by 1,2-addition. 1,4-Bis[2-(triisopropylsilylethynyloxy)phenyl]benzene is shown to undergo a dual intramolecular insertion reaction leading to the formation of pentacyclic condensed aromatics.