Synthesis of 2H-Indazoles via Lewis Acid Promoted Cyclization of 2-(Phenylazo)benzonitriles
摘要:
Lewis-acid promoted "coarctate" cyclization of 10 2-(phenylazo) benzonitrile derivatives furnishes the isoindazole ring system in ca. 65-95% yield. A plausible mechanism for this unusual transformation is proposed.
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