Substituent Effects in the Preparation of Naphthacenes by the Coupling Reaction of Diyne‐Derived Zirconacyclopentadienes with Tetraiodobenzene

The synthesis of a series of substituted naphthacene derivatives through the coupling reaction of zirconacyclopentadienes with diiodobenzenes is reported. A reaction of bis(propargyl)benzenes with zirconacene dibutyl afforded the corresponding tricyclic zirconacyclopentadienes, which reacted with o-diiodobenzenes to afford the corresponding dihydronaphthacenes. The yields of the coupling reactions were dependent on the substituents on both of the zirconacycles and o-diiodobenzenes. The reactions of diphenyl-substituted zirconacycles gave higher yields than those of the alpha,alpha'-dialkyl-substituted derivatives. The iodide functions thus introduced allowed further introduction of substituents by well-established cross-coupling reactions after construction of the naphthacene skeletons.