Lewis Acid Catalysis with Cationic Dinuclear Gold(II,II) and Gold(III,III) Phosphorus Ylide Complexes

The.dinuclear gold(II,II) and gold(III,III) complexes [Au-2(mu-PY)(2)(MeCN)(2)]OTf2 (2-OTf2) and [Au-2(mu-PY)(2)(mu-CH2)(MeCN)(2)]OTf2 (3-OTf2) (PY = [(CH2)(2)PPh2](-)) have been synthesized and evaluated as Lewis acid catalysts for Mukaiyama addition and alkyne hydroamination reactions. 2-OTf2 and 3-OTf2 provide similar or improved catalytic activity for these reactions compared to the commonly used gold(I) Lewis acids Ph3PAuOTf and IPrAuOTf. The versatile Lewis acidity of 2-OTf2 was further demonstrated by its superior performance in a cascade reaction involving intramolecular hydroamination followed by intermolecular conjugate addition to generate a 2,3-substituted indole.