Synthesis Of DBU-based Alkaline Ionic Liquids And Their Performances In Catalyst

Cyclic carbonates and amides are widely used in the fields of biomedical intermediates,electrochemistry,organic synthesis,etc.It is of great significance to efficiently synthesize cyclic carbonates and amides under green and mild conditions.However,the existing catalysts have some problems such as high price,difficulty in recycling,harsh reaction conditions,organic solvent addition,and complicated reprocessing.In this thesis,two novel DBU（1,8-diazabicyclo[5.4.0]undec-7-ene）based alkaline ionic liquids（[DBUH]₂[Cys]and[DBUH][Cl CH₂COO]）were designed and prepared and used to efficiently catalyze the CO₂cycloaddition reaction and the amidation reaction of carboxylic acid and amine under mild,green and solent-free conditions,respectively.The main findings are as follows:（1）Biomass-based alkaline ionic liquid[DBUH]₂[Cys]was synthesized for the first time using L-cysteine and DBU as materials,and the ionic liquid was used in the cycloaddition reaction of CO₂ and epoxides.The results showed that[DBUH]₂[Cys]could efficiently catalyze this reaction at room temperature and atmospheric pressure,and the yield of cyclic carbonate could reach 96%.After the reaction,the product and[DBUH]₂[Cys]were easy to separate,and the catalytic activity of[DBUH]₂[Cys]did not decrease significantly after 5cycles,indicating its high stability.The reaction mechanism showed that the anions and cations of[DBUH]₂[Cys]had synergistic catalytic effects,especially the-S^-in[Cys]^2-enhanced the catalytic effect of[DBUH]₂[Cys].The results above provide a new idea for the preparation of sulfur-containing ionic liquid catalysts.（2）A novel alkaline ionic liquid[DBUH][Cl CH₂COO]was synthesized firstly with chloroacetic acid and DBU as the materials,and the ionic liquid was used in the amidation reaction of amine and carboxylic acid.The results showed that[DBUH][Cl CH₂COO]could efficiently catalyze the reaction of amines and carboxylic acids in equimolar ratios under mild,solvent-free conditions with high yield Amides.After the reaction,the product and the catalyst were easy to separated.[DBUH][Cl CH₂COO]had high stability,and the catalytic activity did not decrease significantly after being recycled for 4 times.Besides,[DBUH][Cl CH₂COO]has excellent universality.The possible reaction mechanism showed that the N-H bond of the cation and the proper basicity of the anion in[DBUH][Cl CH₂COO]were the keys to its high catalytic activity.This novel ionic liquid will provide new ideas for the design and preparation of catalysts in amination reactions.