The Cobalt-Way to Heterophenylenes: Syntheses of 2-Thianorbiphenylenes, Monoazabiphenylenes, and Linear 1-Aza[3]phenylene {Biphenyleno[2,3-a]- cyclobuta[1,2-b]pyridine}.

CpCo(CO)₂ catalyzes the cocyclization of ortho-diethynylthiophenes and -pyridines with alkynes to construct the corresponding thia- and azaphenylenes. This strategy is applied to the synthesis of linear 1-aza[3]phenylene, the first higher heterophenylene. [ABSTRACT FROM AUTHOR]