One-pot N-alkylation of primary amines to secondary amines by gold clusters supported on porous coordination polymers

Gold clusters and nanoparticles were deposited on the three kinds of porous coordination polymers (PCPs), MOF-5, CIPIL-2, and Al-MIL53 by the solid grinding method. The size of Au particles depended on the kinds of PCPs and increased in the order of Al-MIL53 < CPL-2 < MOF-5. The mean diameter of Au particles supported on Al-MIL53 was estimated to be 1.6 nm by HAADF-STEM. Such small Au clusters on Al-MIL53 can catalyze one-pot synthesis of secondary amines from primary amines by sequential oxidation/hydrogenation owing to the remarkable improvement of hydrogenation efficiency of imine. Gold clusters deposited on Al-MIL53 can also promote N-alkylation of amine with alcohol to form a secondary amine under N-2 atmosphere without using O-2 and H-2.