Application Research Of Imidazolium-based Ionic Liquids In Electrophilic Arylthiolation And Nitroreduction

Imidazolium-based ionic liquids are widely used in the field of organic synthesis due to their advantages of modifying easily,low vapor pressure and easy to recycle.The thesis aims to design a recyclable green reaction system based on the structure and properties of imidazolium-based ionic liquids and study its applications in the synthesis of diaryl sulfides and arylamines.First,a new way was developed to synthesis diaryl sulfides by aromatic electrophilic substitution reaction of the electron-rich aromatics in the presence of mineral acids,in which imidazolium-based ionic liquid[Hmim]Br and sodium arylsulfinates were used as the solvent and the sulfur source respectively.Meanwhile,[Hmim]Br was also used as a reducer during the reaction.Under the optimal conditions,electron-rich organic compounds,such as phenols,arylamines,indoles and other heterocyclic compounds,can be easily transformed into corresponding products,and the yields are as high as 97%.In addition,the reaction mechanism was studied by control experiments,and the reducibility of bromide anion was also confirmed.The experiments on the recovery of ionic liquid showed that the system can be reused 10 times without any obvious effect on the yield of the target product.At the same time,the method features simple operation and mild reaction conditions,thereby making it suitable for large-scale industrial production.Secondly,a stable and recyclable aqueous vesicular palladium catalyst system was designed to synthesis arylamines by reducing aromatic nitro compounds under relatively mild conditions,in which the Pd nanoparticles were stabilized by the PEG-grafted imidazolium-based ionic liquids.In the reaction,hydrazine hydrate was used as a reducer,avoiding the use of hydrogen.The morphology of ionic liquids in the aqueous phase was also characterized by dynamic light scattering and transmission electron microscopy,and the vesicles formed in water were confirmed.In addition,the size of the vesicles was found to be inversely proportional to the length of the alkyl chain on the imidazolium cation,inversely proportional to the ionic liquid concentration,and inversely proportional to the product yield.It is believed that small-sized vesicles can contribute to disperse Pd nanoparticles and improve its stability,which leads to high yields,after the analysis.Through the recovery experiments,it was found that the system can be reused for 4 times without any significant effect on the yield of the target products.