Highly selective formation of imines catalyzed by silver nanoparticles supported on alumina

The oxidative dehydrogenation of alcohols to aldehydes catalyzed by Ag nanoparticles supported on Al2O3 was studied. The catalyst promoted the direct formation of imines by tandem oxidative dehydrogenation and condensation of alcohols and amines. The reactions were performed under mild conditions and afforded the imines in high yield (up to 99%) without any byproducts other than H2O. The highest activity was obtained over 5 wt% Ag/Al2O3 in toluene with air as oxidant. The reactions were also performed under oxidant-free conditions where the reaction was driven to the product side by the production of H2 in the gas phase. The use of an efficient and selective Ag catalyst for the oxidative dehydrogenation of alcohol in the presence of amines gives a new green reaction protocol for imine synthesis.

Graphical AbstractA green method to synthesis imines by aerobic oxidative coupling of amines and alcohols under mild reaction conditions with Ag/Al2O3 as catalyst was shown.Figure optionsDownload full-size imageDownload as PowerPoint slide