Regioselective synthesis of 1-arylindazoles via N-arylation of 3-trimethylsilylindazoles

The copper(II)-catalyzed cross-coupling reaction of 3-trimethylsilylindazoles bearing substituents on the benzene ring with arylboronic acids regioselectively gave the corresponding 1-aryl-3-trimethylsilylindazoles and no 2-aryl isomers were formed at all. Moreover, the trimethylsilyl group of the resulting indazoles was easily removed by treatment with ethanolic KOH to give 1-arylindazoles.