A palladium-catalyzed domino reaction to access 3-amino-2H-indazoles from hydrazines and 2-halobenzonitriles

The development of a novel selective synthesis of 3-amino-2H-indazoles from readily available 2-halobenzonitriles is presented. The reaction proceeds through a domino reaction sequence, consisting of a regioselective palladium-catalyzed coupling of monosubstituted hydrazines with 2-halobenzonitriles, followed by an intramolecular hydroamination through a 5-exo-dig cyclization and subsequent isomerization to directly afford a wide variety of substituted 2H-indazole analogues in good to excellent yields