Synthesis And Application Research Of Novel Peg Functionalized Ionic Liquids

Green Chemistry as a new concept was firstly proposed by American Chemical Society in1991. Then it became the main direction of chemical development worldwide. The ideas of reducing emissions of toxic substances, saving energy, and sustainable development are the starting points when scientists design new chemical reactions currently. Every year hundreds of tons of chemical wastes are discharged into the nature, most of which are organic solvents. This is a heavy burden on the natural environment. Developing organic reactions using green solvents can solve this problem radically. Among the green solvents which have been reported, water is an abundant and nontoxic solvent. It has been applied in many organic reactions.Dimethyl carbonate is a new non-toxic chemical reagent and it has important applications in chemical industry, such as methylation reagent, carbonylation reagent and solvent. At present the main methods for the preparation of dimethyl carbonate are transesterification and oxidation carbonylation. Since transesterification achieve the CO2conversion with any toxic gas, it has become a hot research area. However, compared with other methods, it in includes two steps, bringing complicated operation, high cost and other issues. Most reported systems which prepare dimethyl carbonate by the use of epoxides, CO2and methanol need high pressure conditions. Our group has been investigated the environment-friendly system in order to complete the reactions under green and mild conditions. On this purpose, we mainly report the following contents in this paper:1. We prepared a series of poly(ethylene glycol)-functionalized ionic liquid IL1-7by means of the deceloped methods in our group and characterized their structures. Synthesis of the ionic liquids was conducted without inert gas, solvents and catalyst. Most yields of the synthesis reactions were more than80%.2. We applied the PEG--functionalized ionic liquids to the aqueous Suzuki reaction. After conducting the optimization of bases and ligands, we found that the imidazolium salts which could form N-heterocyclic carbenes can promate the reaction. Under the optimal condition, substrates bearing either electron-donating or electron-withdrawing groups provided more than89%isolated yields within25min.3-Pyridyl bromides bearing different substituents provided more than87%isolated yields with60min.3. We prepared a ionic liquid IL8by means of the traditional methods in our group and applied it and bases to develop a one-pot process for the preparation of dimethyl carbonate by using ethylene oxide, CO2and methanol as raw materials. The dimethyl carbonate yield was more than30%and the selectivity of dimethyl carbonate ethylene carbonate was89%.After optimizing the bases, dimethyl carbonate yield can reach more than70%. Then we further investigated the activity of this system on the one-pot process for the preparation of dimethyl carbonate by using propylene oxide, CO2and methanol as raw materials. After conducting the optimization of bases, pressure and temperature, it exhibits good catalytic activity. When the initial CO2pressure was only0.5MPa, the dimethyl carbonate yield was more than50%and the selectivity of dimethyl carbonate and propylene carbonate was more than80%.