Palladium complexes supported by (o-biphenyl)P(t-Bu)(2) (3) or (o-biphenyl)PCy2 (4) are efficient catalysts for the catalytic amination of a wide variety of aryl halides and triflates. Use of ligand 3 allows for the room-temperature catalytic amination of many aryl chloride, bromide, and triflate substrates, while ligand 4 is effective for the amination of functionalized substrates or reactions of acyclic secondary amines. The catalysts perform well for a large number of different substrate combinations at 80-110 degrees C, including chloropyridines and functionalized aryl halides and triflates using 0.5-1.0 mol % Pd; some reactions proceed efficiently at low catalyst levels (0.05 mol % Pd). These ligands are effective for almost all substrate combinations that have been previously reported with various other ligands, and they represent the most generally effective catalyst system reported to date. Ligands 3 and 4 are air-stable, crystalline solids that are commercially available. Their effectiveness is believed to be due to a combination of steric and electronic properties that promote oxidative addition, Pd-N bond formation, and reductive elimination.
“Simple, Efficient Catalyst System for the Palladium-Catalyzed Amination of Aryl Chlorides, Bromides, and Triflates”, J. Org. Chem., 2000, 65(4), 1158-1174.