A Pronounced Anionic Effect in the Pd‐Catalyzed Buchwald–Hartwig Amination Reaction Revealed in Phosphonium Salt Ionic Liquids

Abstract The Pd‐mediated Buchwald–Hartwig amination reaction of aryl halides in a phosphonium salt ionic liquid consisting of a trihexyl(tetradecyl)phosphonium cation with a range of anions has been investigated. A pronounced anionic effect was uncovered with the reaction proceeding readily with weakly nucleophilic diarylamines only in the presence of noncoordinating anions. A mechanism is postulated to explain these results and it involves a rate‐limiting ligand exchange step that proceeds through a dissociative pathway.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)