Functionalized Polymer-Supported Pyridine Ligands for Palladium-Catalyzed C(sp3)–H Arylation

The use of ligands to tune the reactivity and selectivity of transition-metal catalysts for C(sp3)–H bond activation is a current central challenge. One of us previously developed an uncommon example of a homogeneous catalyst that performs controlled C(sp3)–H arylation using pyridine derivatives as ligands, along with Pd [Science, 2014, 343, 1216–1220]. In this work, we report a functionalizable and tunable polymer support used in the immobilization of pyridine derivatives that yields a soluble, polymeric ligand platform facilitating C(sp3)–H activation reactions with good yields, selectivities differing from the homogeneous catalyst, and recovery of Pd. Unlike the homogeneous system, the supported catalysts in Pd-catalyzed C–H monoarylation reactions respond sensitively to the steric hindrance of the coupling partners.