Selective Reduction Of Aromatic Aldehydes And Reductive Amination Of Aldehydes/Ketones Under Mild Conditions

Alcohols and amines are important compounds in synthetic organic or bioorganic chemistry.They are also important intermediates in pharmaceuticals,agrochemicals,fine chemicals,polymers,dyes and plasticizers,with excellent economic value.In the laboratory and industry,the reduction of organic compounds are important reactions in which the catalyst plays an important role.In this thesis,a novel heterogeneous palladium nanocatalysts?Pd-NPs?were chemically synthesized from the metal precursor K₂PdCl₄ and varied ligands.The catalysts have high selectivity and activity,can be reused and recycles.After several repeated experiments,still have high catalytic activity.Using one of the ligands was found to be best,Pd-NPs completed the following two parts:?1?selective reduction of aromatic aldehydes;?2?reductive amination of aldehydes and ketones.The first part of this thesis is that under room temperature and pressure,H₂ is used as the hydrogen source and water is used as solvent.Aromatic aldehyde can be efficiently and selectively reduced to their corresponding aromatic alcohols using palladium-based catalyst?Pd-ligand?.Initial reactions were carried out using benzaldehyde as the model substrate,the effects of Pd-ligands,loading of catalyst,and reaction times on the yields of aromatic alcohols were investigated.Among all the tested conditions,the best one is:ligand,o-phenylenediamine;catalyst loading,1.0 mg;and reaction time,5 h;under which,the yield of the desired product benzyl alcohol was obtained to be up to 99%.The structures of all products were characterized by ¹H NMR and ¹³C NMR.The newly synthesized Pd-NPs were characterized by TEM,FT-IR,XPS,XRD,EA,ICP-OES.The second part of the thesis is that under room temperature,1 bar of H₂ is used as the hydrogen source,and green non-pollution water?pH=2.0?is used as the solvent to achieve efficient reductive amination by using palladium-based catalyst?Pd-ligand?.Initial reactions were carried out using benzaldehyde as the model substrate,reductived amination to benzylamine,the effects of Pd-ligands,ammonia sources,pH and temperature on the yields of benzylamine were investigated,and obtained the optimal conditions.Under this optimal condition,the substrates range were extended,and a large amount of aldehydes and ketones were reductived amination to the corresponding amines,products structure were characterized by ¹H NMR and ¹³C NMR.The newly synthesized Pd-NPs were characterized by TEM,FT-IR,XPS,XRD,EA,ICP-OES.