Electronic Role of 3‑Iminophosphine Ligands in Palladium-Catalyzed Intermolecular Hydroamination

This study of the electronic characteristics of (3-iminophosphine)­allylpalladium triflate complexes has yielded catalysts with moderate to high activity for the hydroamination of monosubstituted allenes utilizing a wide range of amines. Herein, a new series of these catalysts was synthesized by varying the group on the imine moiety in order to explore the effect of the electronics of the ligand’s imine on the catalytic activity for intermolecular hydroamination reactions. Four amine substrates were examined in the catalytic hydroamination of cyclohexylallene, and apparent first-order rate constants were obtained by ¹H NMR spectroscopy. Kinetic isotope effect studies were also performed in order to support a new proposed catalytic cycle in the hydroamination of cyclohexylallene with secondary amines using [(3IP)­Pd­(allyl)]­OTf catalysts.