Palladium-catalyzed highly selective ortho-halogenation (I, Br, Cl) of arylnitriles via sp2 C-H bond activation using cyano as directing group.

A palladium-catalyzed ortho-halogenation (I, Br, Cl) of arylnitrile is described. The optimal reaction conditions were identified after examining various factors such as catalyst, additive, solvent, and reaction temperature. Using cyano as the directing group, the halogenation reaction gave good to excellent yields. The method is compatible to the arylnitriles with either electron-withdrawing or electron-donating groups. The reaction is available to the substrate in at least gram scale. The present method was successfully applied to the synthesis of the precursors of paucifloral F and isopaucifloral F.