A series of phosphine-ligated palladium precatalysts based on N-methyl- and N-phenyl-2-aminobiphenyl have been developed. Substitution at the nitrogen center prevents the presence of traces of aminobiphenyls that contain a free –NH2 group from contaminating cross-coupling products. These precatalysts produce N-substituted carbazoles upon activation, which cannot consume starting materials. These precatalysts were efficiently generated from 2-aminobiphenyl with minimal purification and found to be highly effective in Suzuki–Miyaura and C–N cross-coupling reactions.
“N-Substituted 2-Aminobiphenylpalladium Methanesulfonate Precatalysts and Their Use in C–C and C–N Cross-Couplings”, J. Org. Chem., 2014, 79(9), 4161 - 4166.