Basic function of Cu/Ni-based catalyst in a colloidal state for one-pot amination alcohols to N,N-dimethyl tertiary amines

One-pot amination of fatty alcohols with dimethylamine at normal pressure, using Cu/Ni-based colloidal catalyst stabilized by barium sterate (Cu/Ni/Ba colloidal catalyst, Cu:Ni:B = 5:1:1). proceeded without charging bulk hydrogen with an amine yield of more than 90%. It demonstrated the effective use of active hydrogen, generated by the dehydrogenation of a starting alcohol over copper, for the following hydrogenolysis of an aldehyde-dimethylamine adduct to form the final product, N,N-dimethil-long alkyl-tertiary amines. The basic function generated by the combination of copper and nickel, especially in a colloidal state, was named as “Self-supplying System for Active Hydrogen”. On the other hand, reductive amination of aldehydes with dimethylamine, in the presence of hydrogen flow at a normal pressure using the same colloidal catalyst, proceeded with an amine yield of 40–80%, and significant amount (12–26%) of aldols were formed. These observations demonstrated the essential difference between one-pot amination of alcohols containing active hydrogen and reductive amination of aldehydes in the presence of bulk hydrogen which has to be activated separately. This is the first description of basic function of Cu/Ni-based catalyst by the original inventors of the catalytic system. More than five-fold increase in catalytic activity by incorporation of calcium stearate with Cu/Ni was observed for one-pot amination of fatty alcohols. Comparison of catalytic activity of Cu/Ni-based catalyst in a colloidal state and in a solid state showed superiority of the former catalyst in catalytic activity, 40–50 times higher based on a unit amount of copper.