Assembly of Substituted 3-Aminoindazoles from 2-Bromobenzonitrile via a CuBr-Catalyzed Coupling/Condensation Cascade Process

CuBr-catalyzed coupling reaction of 2-halobenzonitriles with hydrazine carboxylic esters and CuBr/4-hydroxy-L-proline-catalyzed coupling reaction of 2-bromobenzonitriles with N'-arylbenzohydrazides proceed smoothly at 60-90 degrees C to provide substituted 3-aminoindazoles through a cascade coupling/condensation (or coupling/deacylation/condensation) process. A wide range of 3-aminoindazoles with substituents at both the 1-position and the phenyl ring part can be prepared from the corresponding coupling partners.