The role of protons in hydroamination reactions involving homogeneous and heterogeneous catalysts

Abstract

The addition of amines to CC double and triple bonds using different transition metal catalysts was investigated. Lewis acidic complexes of rhodium, palladium, copper and zinc are effective catalysts for the cyclisation of 3-aminopropyl-vinylether and 6-aminohex-1-yne. The catalytic activity of these homogeneous catalysts is significantly increased in the presence of catalytic amounts of Brønsted acids. The higher activity of corresponding heterogeneous catalysts, here shown for zinc ion exchanged beta zeolites, is probably related to residual protons in the material. The respective role played by Lewis acidic metal centres and protons in the catalytic systems is discussed. It is concluded that Brønsted and Lewis acids, and their respective properties, have to be taken into account in the rational design of hydroamination processes mediated by late transition metals.