Atom-Economic Route to Cyanoarenes and 2,2'-Dicyanobiarenes via Iron-Catalyzed Chemoselective [2 + 2 + 2] Cycloaddition Reactions of Diynes and Tetraynes with Alkynylnitriles.

An efficient protocol for the synthesis of cyanoarenes has been developed via an iron-catalyzed chemoselective [2 + 2 + 2] cycloaddition reaction of diynes with alkynylnitriles under mild reaction conditions with good to excellent yields. The reaction is catalyzed by the combination of FeCl2·4H2O as a metal source, 2-(2,6-diisopropylphenyl)iminomethylpyridine (dipimp) as a ligand, and Zn as a reducing agent in DME solvent. The protocol was further extended to the synthesis of 2,2'-dicyanobiarene skeletons from the reaction of tetraynes with alkynylnitriles.