Phosphine ligands, such as triphenylphosphine or the Trost ligand, have been used to greatly expand the scope of the Tsuji–Trost reaction. These ligands can modulate the properties of the palladium catalyst such as steric bulk as well as the electronic properties. Importantly, these ligands can also instill chirality to the final product, making it possible for these reactions to be carried out asymmetrically as shown below.