Catalytic Scaffolding Ligands: An Efficient Directing Group Strategy Kian Tan, Department of Chemistry, Boston College The control of chemo-, regio-, and stereoselectivity is a paramount goal for any synthetic chemist. We have launched a program aimed at developing general approaches for controlling selectivity in organic reactions. Directing-group strategies are a powerful means of controlling selectivity and enhancing reactivity in chemical transformations; however, they often require the use stoichiometric quantities of metal-binding ligands such as phosphines or heterocycles. Such directing group strategies, though a powerful means of controlling selectivity, are hampered by the necessity of incorporating and removing the directing group with additional synthetic steps. We have developed a strategy that overcomes these limitations with an appropriate ligand that both reversibly and simultaneously binds the metal catalyst and a common organic functionality on the substrate (Scheme 1). By using a ligand as a scaffold to temporarily join the catalyst and substrate together, the power of directing groups to control selectivity is coupled to the practicality of catalysis. The value of our strategy is that we can apply a synthetically useful functional group to bind to the ligand, and then tailor the ligand for optimal performance in the desired transformation.