Abstract
A cascade reaction for 1,8-dibromobiphenylene A with arylboronic acid B toward an unusual product C was comprehensively investigated. The initially formed Suzuki product D underwent an unprecedented palladium-catalyzed cycloisomerization, yielding E with a unique 5-8-5-membered ring framework. In most cases, E proceeded via thermal rearrangement to form C. This work also examined the scope and limitations of the cascade reaction, probed its mechanism, and verified the structures of C and E by X-ray crystallography.