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 [Au2(μ-PY)2(MeCN)2]­OTf2 (2-OTf2) and [Au2(μ-PY)2(μ-CH2)­(MeCN)2]­OTf2 (3-OTf2) (PY = [(CH2)2PPh2]−) 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.