Extended Research On The Applications Of Functional Ionic Liquids As Solvents/Catalysts In Organic Reactions

Chemistry industry is closely linked to our daily lives, which does not only create a variety of conveniences for us but also bring about numerous environmental pollutions and hazards. Ionic liquids (ILs) provide a feasible way to solve the pollution problems and promote to achieve sustainable development goals of green chemistry owing to the less volatile, non-flammable, wild liquid range, recyclable and other features. The unique ionic environment which ILs provide is different from molecular solvents and plays an important role in stabilizing the reactive catalytic species or the reaction intermediates, while molecular solvents lack these unparalleled advantages. IL is not only toxic volatile solvent ideal alternative, but also contributes much in speeding up the reaction rate, increasing the yield and product selectivity. Therefore IL is widely used in engineering technology, organic synthesis, material science and other fields. Task-specific ionic liquids (TSILs) with designable structures can be designed according to the specific needs of the reaction, which is the source of ILs to flourish.Based on the above idea, we studied the application of functional ILs as solvent or catalyst in organic reaction in this thesis. The work mainly consists of two sections. The first part is the research about application of IL in pyridazine derivative synthesis reaction as the reaction medium. The second part is the preparation of new Bronsted-Lewis complex basic functional ILs and their use as a catalyst in Mannich reaction. The details are as follows:1. An efficient and environmentally friendly procedure for synthesis of pyridazine derivatives in imidazolium ionic liquidsAn efficient and environmentally friendly procedure was developed for synthesis of pyridazine derivatives. A series of imiidazolium ILs Bmim]Br,[Bmim]BF4,[Bmim]PF6,[Bmim]HSO4,[Bm2im]Br,[Bp]Br,[Bhmim]Br were synthesized and used in preparation for pyradizine derivatives as benign solvents and catalysts. ILs with good ability to form hydrogen bond with1,2,4,5-tetrazine show excellent catalytical activities while the yields are lower in weak hydrogen bond donor such as [Bm2im]Br and [Bp]Br. We chose the synthesis in low-cost [Bmim]Br as a model reaction and study the effect of reaction temperature, time, reactant molar ration on the product yields to optimize the reaction conditions.[Bmim]Br was also investigated to catalyze reactions of1,2,4,5-tetrazines with a variety of dienophiles. Furthermore,[Bmim]Br showed excellent reusabilities with high desired product yields after recycled for six times. Finally, we studied the interaction between [Bmim]Br and reactants and proposed the possible reaction mechanism by the assistance of1HNMR spectrum.2. Mannich reaction catalyzed by novel Bronsted-Lewis complex basic ionic liquidThree kinds of novel Bronsted-Lewis complex basic ionic liquid [DEAEPy]OH,[DEAEPy]CH3COO,[DEAEPy]HCO3were prepared and characterized by’HNMR, FT-IR to certify their structure. Novel ILs were applied to catalyze one-pot three component Mannich reaction of benzaldehyde, aniline and cyclohexanone in comparison with other conventional pyridine ILs. The result revealed that the catalytic activities were closely related to their basicities. Selecting the best catalytic performances [DEAEPy]OH as a catalyst in Mannich reaction, we optimize reaction conditions in three aspects from different solvents, amount of catalyst, reaction time. After completion reaction,[DEAEPy]OH was easily reused to another run without further purification. In addition, we explored the possible reaction pathway of Mannich reaction in [DEAEPy]OH, and proposed cooperative catalysis by the cation and anion.