Non-noble Metal Catalyzed Hydrogen Transfer Coupling Reactions To Synthesize Amine Compounds

With the rapid development of modern industry,non-renewable fossil energy with limited reserves is being increasingly consumed,accompanied by a series of pollution problems to the environment,such as: greenhouse effect,PM 2.5,acid rain,etc.these problems pose serious threat to human living environment.More and more researchers are committed to the green and sustainable catalytic methods to generate various high-value-added chemicals.Therefore,the development of catalytic systems with mild、green reaction conditions and compatibility with industrial production is particularly important for the development of human society.The noble metal catalysts have been widely studied in the field of catalysis for their excellent activity、 selectivity and stability.However,it is undeniable that their exorbitant price and limited reserves are the disadvantageous for the large-scale applications.The non-noble metal catalysts,compared with noble metal catalysts,have attracted the attention to vast researchers for their low price,abundant reserves,widely distribution,and excellent thermal stability.At present,numbers of researchers are devoted to improving the catalytic activity of non-precious metal catalysts in terms of catalysis to the partial replacement or full replacement of precious metal catalysts used in industries.At the same time,amines,which is an important chemical intermediate,are widely used in the production of medicines,pesticides,and polymers.Through the process of catalytic hydrogen transfer reaction,amine compounds can be obtained from the nitro compounds and further be coupled with the aldehyde compounds or the alkylating reagent to generate the imines or N-alkylation products.These reactions extend the application range of the nitro compounds and provide an effective method for the production of amines and their derivatives.The catalytic hydrogen transfer reactions avoid the use of flammable and explosive hydrogen,further reducing the requirements on reaction equipment and increasing the safety of reactions.Here,we developed a series of non-noble metal catalysts based on cobalt and copper described as followings:1.A nitrogen-doped carbon material supported cobalt catalyst was designed and used in a one-pot process to catalyze reductive amination of carbonyl compounds with nitro compounds to prepare secondary amines.ZIF-67 as an important kind of metal organic framework,which is composed of Co²⁺and imidazole ligands.Herein,a graphene-directed assembly route was used to prepare the nitrogen-doped carbon-based cobalt catalysts,in which Co nanoparticles were embedded in the nitrogen-doped carbon structure.As prepared catalysts were found to be highly active and stable for one-pot reductive amination of carbonyl compounds with nitro compounds with formic acid as the hydrogen donor.2.Carbon materials and metal oxide co-supported copper catalysts were designed for the synthesis of N-methylamines using methanol both as the methylation agent and the reductant agent,which leads a high atom efficiency and the avoidance of the separation of amines.By selecting filter paper as a carbon source that can absorb the solution containing metal ions,which is mainly due to the rich pore structure inside the filter paper.The Cu/MgO-C-T catalysts（T stands for calcination temperature）were obtained by calcining the filter paper that has adsorbed copper ions and magnesium ions.The catalyst has the advantages of simple and rapid preparation method and cheap raw materials.To our pleasure,the as-prepared Cu/MgO-C-T catalyst demonstrated the excellent activity towards the one-pot synthesis of N-methylated amines from nitro compounds with methanol,in which the basic MgO assisted the dehydrogenation of methanol and its mesoporous structure with large surface area facilitated the mass transfer of the reaction molecules and the products.