Study On Activated Carbon Supported Ruthenium Nanoparticles Catalyzed Cross-coupling Of Alcohols With Amines And Oxdation Of Amines

The cross-coupling of alcohols with amines to imines and the oxidation of amines to the corresponding nitriles are very important reactions in organic and medical synthesis,using molecular oxygen as oxidant to realize these processes meets the requirements of green chemistry.In this paper,the x%Ru/AC?x%represents the weight percentage of ruthenium in the catalyst?catalysts were prepared by the method of liquid phase reduction.The x%Ru/AC catalysts were applied to the cross-coupling of alcohols with amines to imines with oxygen as oxidant under atmospheric pressure.The optimized conditions were obtained by investigating the ruthenium content in the catalyst,catalyst loading,the molar ratio of alcohols to amines,reaction temperature and the types of solvent with the cross-coupling of benzyl alcohol with aniline to N-?phenyl?benzylamine as a model reaction,which were:5%Ru/AC in 5ml toluene,the molar ratio of benzyl alcohol to aniline is 1:1.1,catalyst loading5 mol%,reaction temperature 90?C and oxygen balloon.The catalytic system showed good performances on the cross-coupling of aromatic,heterocyclic primary alcohols with aromatic,aliphatic primary amines to the corresponding imines under the optimized conditions,the yield of imines is up to 90%?GC?.The catalysts were characterized by XRD,TEM-EDX,and N₂ adsorption-desorption analysis and ICP-AES.Ru particles well dispersed on the surface of the pores,the Ru nanoparticles were nanometer scale,and no obvious leaking of Ru took place during the catalytic run.Meanwhile,the catalysis of the catalysts is very sensitive to the Ru nanoparticle sizes.The 5%Ru/AC performed best among the catalysts,the Ru particle sizes in which is about 1.1 nm.Aggregation of Ru nanoparticles due to weak Ru-AC interactions is the main reason leading to the deactivation of the catalyst.The x%Ru/AC?x%represents the weight percentage of ruthenium in the catalyst?catalysts were prepared by the method of liquid phase reduction.The x%Ru/AC were applied to the oxidation of amines to nitriles.The optimal reaction conditions were obtained with the oxidation of benzylamine to benzonitrile as a model reaction by investigating the effects of catalysts,catalyst loading,temperature,the pressure of oxygen and the type of solvent on the reaction.The optimized conditions were:5%Ru/AC in 5ml toluene,substrates 1mmol,catalyst loading 3 mol%,reaction temperature 150?C and oxygen pressure 0.5 MPa.The catalytic system showed good performances on the cross-coupling of aromatic,heterocyclic and aliphatic primary amines to the corresponding nitriles under the optimized conditions,and the yields were higher in the cases of aliphatic primary amines,which were more than 90%?GC?.The catalyst was easily recovered and no ruthenium leaking was found in the catalytic run.From the result of the TEM characteration,the aggregation of Ru nanoparticles during the catalytic run is the main reason causing the deactivation of the catalyst.