Studies On The Application Of Several Basic Imidazolium Ionic Liquids In Some Organic Reactions

There is a series of problems such as equipment corrosion,additional cost of production and treatment,waste of resource and environmental pollution,etc.in the traditional ways of organic catalysis.In recent years,due to their unique physical and chemical properties,ionic liquids not only can replace traditional organic solvents as newly green media,but also exhibit unique catalytic activity in the organic reactions.For basic imidazolium ionic liquid,on the one hand,it can replace the traditional base and organic solvent in the organic reaction,reducing the corrosion of the equipment and environmental pollution;On the other hand,the basic anion could deprotonate the C2-H of the imidazolium cation and then enable the formation of a nucleophilic nitrogen heterocyclic carbene(NHC)in a basic imidazolium ionic liquid in-situ.Therefore,basic imidazolium ionic liquid has great development potential and application prospect in organic reactions.However,the related report about the basic ionic liquids was rare,and the catalytic mechanism of ionic liquids in these reactions is still unclear,which greatly limits the further development of ionic liquids and their industrial applications.Based on the above problems,five kinds of imidazolium ionic liquids composed of basic anions were designed and synthesized in this paper.These ionic liquids were used as green solvents and catalysts for benzoin condensation reaction,transesterification reaction,cyanosilylation reaction and the carbon dioxide conversion reaction which can be catalyzed by NHC or base catalysts.The catalytic effect of the ionic liquids and their influencing factors have been studied in detail.At the same time,the catalytic mechanism of ionic liquids was studied by NMR spectroscopy.The interaction between basic imidazolium ionic liquids and reaction substrates were analyzed.The role of anion or cation in the reaction process was presumed,which could provide a theoretical reference for the further development of ionic liquid and the promotion of its industrialization process.As a part of the National Natural Science Foundation of China(NO.21573061),main research contents of this paper are as follows:1.Five basic imidazolium ionic liquids consisting of basic anions([Im]~-,[BnIm]~-,[4-Triaz]~-,[BTA]~-and[Ac]~-)were synthesized and purified by anion exchange method in two steps.Then these ionic liquids were characterized by NMR spectroscopy.The water content and thermal decomposition temperature of these basic ionic liquids were determined.2.These basic imidazolium ionic liquids were applied in benzoin condensation reaction.The catalytic activity of these ionic liquids was examined.Various influence factors were investigated,including the kinds of anions and cations,the amount of ionic liquids,the water content,the temperature and the solvent.By the acquisition and characterization of the NHC-PhCHO adduct of the reaction mixture,the participation of the NHC in the reaction was confirmed.A possible catalytic mechanism was proposed.3.To take advantage of their basic activity,these ionic liquids were applied in transesterification reaction and their catalytic activity was examined.Different influence factors were studied in detail,including the kinds of anions and cations,the amount of ionic liquids and the reaction time.The application range of substrate was extended.At the same time,by analyzing the NMR spectra before and after the interaction of ionic liquid with the substrate benzyl alcohol,the role of ionic liquid for the reaction was investigated.A possible catalytic mechanism was obtained.4.In order to exert the nucleophilic ability of the basic anion,these basic imidazolium ionic liquids were used in cyanosilylation reaction and their catalytic activity was tested.The effects of different factors on the reaction were investigated,such as the types and the amount of ionic liquids.And then the range of substrate was expanded.By analyzing the NMR spectra before and after the interaction of ionic liquid with the substrate trimethylcyanosilane(TMSCN),the role of ionic liquid in the reaction was investigated.A possible catalytic mechanism was provided.5.Based on the carbon dioxide adsorption effect by basic ionic liquids and the hydrogen bonding between o-aminobenzonitrile and these ionic liquids,they were used for catalyzing the reaction of o-aminobenzonitrile with carbon dioxide.The influence factors of the reaction were investigated,including the kinds of anions and cations,the amount of ionic liquids,the temperature and the reaction time.The recyclability of ionic liquid was also studied.The interaction between ionic liquid and o-aminobenzonitrile were analyzed by nuclear magnetic resonance,and a possible reaction mechanism was provided.