New phase-separable polyisobutylene palladium catalysts for Buchwald-Hartwig amination reaction

This paper reports the efficient synthesis of the first class ofpolyisobutylene(PIB)-supported palladium-PEPPSI precatalyst (PEPPSI =pyridine-enhanced precatalyst preparation, stabilization, and initiation).The new complexes are employed in Buchwald–Hartwig amination of arylchlorides and are found to be reasonably active in the titled cross-couplingreaction. The supported catalysts are tested in polar (1,4-dioxane and1,2-dimethoxyethane) as well as in aliphatic reaction media (toluene andn-heptane) and display superior activity in the highly lipophilic solvent (n-hep-tane). The catalytic efficacy of PIB-Pd-PEPPSI precatalyst is measured to becomparable to its nonsupported analog. Pd-leaching is determined by induc-tively coupled plasma mass spectrometry (ICP-MS) after a simple liquid/liquid extraction and is found to be 2 ppb in the product phase, translatinginto a recovery of ≈99.8% of the palladium.