PEG-based Dicationic Ionic Liquids Exhibiting Temperature-dependent Phase Behavior And Their Applications In Organic Reactions

Separation and recovery of catalyst with high efficiency plays an important role in green chemistry. New catalytic system possess the thermoregulated biphasic behavior of "mono-phase under high temperature, bi-phase under room temperature" have been attracted much attention due to their advantages of both homogeneous and heterogeneous catalysis with high product yield and the easy separation of product from catalytic system. ILs, as environmental friendly reaction media or catalysis, have attracted increasing attention. And, ionic liquids based on the thermoregulated biphasic behavior have been proposed because of their obvious advantages. In this paper, PEG-DIL and PEG-DAIL have been studied. PEG-1000-based dicationic ionic liquid (PEG₁₀₀₀-DAIL, PEG₁₀₀₀-DIL) exhibiting temperature-dependent phase behavior with toluene (water) and their applications in different organic reactions were studied.Five new neutral PEG-based dicationic ionic liquids (PEG₂₀₀-DIL, PEG₄₀₀-DIL, PEG₁₀₀₀-DIL, PEG₂₀₀₀-DIL, PEG₄₀₀₀-DIL) and two new acidic PEG-based dicationic ionic liquids (PEG₂₀₀-DAIL, PEG₁₀₀₀-DAIL) were synthesized. It was found that PEG₁₀₀₀-DAIL/ toluene system and PEG₁₀₀₀-DIL/toluene system could be formed excellent thermoregulated biphasic system. And PEG₁₀₀₀-DIL/water could be formed "mono-phase under room temperature, bi-phase under high temperature" system. Moreover, PEG₁₀₀₀-DAIL could be used as both solvent and catalyst. Applications of PEG₁₀₀₀-DAIL/toluene thermoregulated system in acetalizations, esterifications, one-pot three-component condensations and Biginelli reactions were investigated. PEG₁₀₀₀-DIL acted as solvent for acetalizations (p-toluenesulfonic acid as catalyst) and nitro-group reduction (FeOOH as catalyst) in PEG₁₀₀₀-DIL/toluene system. And applications of PEG₁₀₀₀-DIL/water system in Knoevenagel reaction and PEG₂₀₀-DAIL in nitration of toluene and nitrolysis of DPT were investigated also. Efects of reaction temperature, reaction time, amount of calalyst, and ratio of raw materials on these reactions were investigated. It was found that these reactions had advantages such as, short reaction time, high yields, easy separation without any apparent loss of catalytic activity and little loss of weight even after more times recycling.PEG-based ionic liquids were developed. Novel "mono-phase under high temperature, bi-phase under room temperature" systems (PEG₁₀₀₀-DAIL/toluene system and PEG₁₀₀₀-DIL/toluene system) and "mono-phase under room temperature, bi-phase under high temperature" system (PEG₁₀₀₀-DIL/water system) have been found highly effective for some organic reactions.