Preparation Of Nickel-based Catalysts And Research On The Synthesis Of Amine Derivatives From Alcohol Dehydrogenation

Traditional chemical reactions should be continuously improved to meet the requirements of green chemistry,from the aspects of raw materials and synthetic methods.The acceptorless dehydrogenation of alcohol has the advantages of atom economy and environmental friendliness.It still has certain research value that to realize the value-added of chemicals by using earth’s abundant base metals as catalysts.In this paper,two nickel homogeneous catalysts and one nickel-supported heterogeneous catalyst were designed and synthesized.Using benzyl alcohol and aniline as template substrates,the effect of different reaction conditions on the product yield was investigated.The target product was selectively synthesized through the optimization of the conditions,and the reaction mechanism of two catalytic systems was discussed.The main research contents and results of this paper are as follows:（1）Bipyridine ligand/Ni Br₂ was used to catalyze the reaction of alcohol and amine in situ.The effects of ligand,base,reaction solvent,temperature and time on the conversion were investigated.The applicability of 13 types of substrates was investigated,and the mechanism of this reaction system for catalyzing alcohol dehydrogenation was discussed.The optimum reaction conditions when the product is secondary amine:the mass ratio of 2,2′-bipyridine-5,5′-dicarboxylic acid/Ni Br₂ is 1（?）1,the base is t-Bu OK,the reaction solvent is toluene,and the reaction temperature 140°C,the reaction time is 48 h,the highest yield is 92%;the optimal reaction conditions when the product is imine:2,2′-bipyridine-5,5′-dicarboxylate/Ni Br₂ material ratio is 2（?）1,the base was t-Bu OK,the reaction solvent was toluene,the reaction temperature was140°C,the reaction time was 42 h,and the highest yield was 93%.The results show that the type of ligand will affect the selectivity of the reaction product.When the ligand is 2,2′-bipyridine-5,5′-dicarboxylic acid,the product secondary amine is obtained,and when the ligand is 2,2′-methyl bipyridine-5,5′-dicarboxylate,the product imine is obtained.Under optimal conditions,the product secondary amine and the imine were selectively obtained in moderate to good yields for different substrates containing electron-withdrawing or electron-donating substituents,respectively.Preliminary mechanism studies showed that under different reaction conditions,the target products were obtained through the outer-layer mechanism and the inner-layer mechanism,respectively.（2）Nickel-supported bipyridyl MOF catalyst Bpy-Ui O-Ni was prepared by mild post-synthesis modification with Ui O-67-bpy as carrier.The catalyst was characterized by XRD,SEM,XPS,FT-IR and other methods.The results showed that Bpy-Ui O-Ni was a regular octahedral crystal with large specific surface area and microporous structure,and the metal nickel was uniformly loaded into the MOF.When aniline and benzyl alcohol were added 0.1 mmol at a ratio of 1:4,Bpy-Ui O-Ni（5 mg）and t-Bu OK（130 mol%）can catalyze reaction between benzyl alcohol and aniline.The conversion rate of the first round of catalysis was up to 100%（the separation yield was96%）.After 4 cycles,the catalytic efficiency of the material did not decrease significantly,which showing a good recyclability.Substrate expansion experiments showed that the catalytic system can obtain a series of N-alkylated products with excellent conversion and selectivity.