Selective Activation of Alcohols in the Presence of Reactive Amines over Intermetallic PdZn: Efficient Catalysis for Alcohol-Based N-Alkylation of Various Amines

Pd-based intermetallic compounds supported on Al2O3 (PdxMy/Al2O3, where M = Bi, Cu, Fe, Ga, In, Pb, Sn, or Zn) were prepared and tested as catalysts for the selective activation of alcohols in the presence of reactive amines, which is highly challenging and is the key strategy for alcohol-based N-alkylation of amines. Although the Pd/Al2O3 catalyst exhibited a high catalytic activity, undesired side reactions such as amine dimerization (via amine activation) and C–O bond scission occurred, resulting in a poor yield of the N-alkylation product. In contrast, the PdZn/Al2O3 catalyst acted as an efficient catalyst for this reaction, displaying high catalytic activities, selectivities, and atom efficiencies and a wide substrate scope. Detailed kinetic and computational studies revealed that the relative affinity of Pd for alcohol and amine drastically changes by the formation of a PdZn intermetallic phase. On monometallic Pd, the adsorption and activation of amines are preferred over those of alcohols in terms...