Synthesis Of Acidic Functional Ionic Liquids And Their Widening Application In Organic Reactions

Along with the deepen understanding of environmental protection, the idea of green chemistry, the concept of functional ionic liquids was proposed. Recent years, acidic functional ionic liquids have received increasing attention for their prominent application in organic synthesis, enzyme catalysis, extraction separation and material science etc. Therefore, it is very important to investigate a cheap, clean, effective and simple method of synthesizing novel acidic ionic liquids, which have small environmental contamination after expiration, design and synthesize new ionic liquids, enrich ionic liquids species, break new domain of research and application area for ionic liquid are required to satisfy the idea of green chemistry.This paper had developed two new kinds of acidic functional ionic liquids: Multiple-SO3H ionic liquids and the ionic liquids with both Br(?)nsted&Lewis. We studied the preparation, characterization of novel acidic ionic liquids and widening application in organic acid catalysis reactions.The synthesis and application of functional ionic liquids include following parts:1. Synthesis of multiple-SO3H ionic liquidsFive multiple-SO3H ionic liquids [Bis-Bs-DABCO][HSO4]2(MIL1).[Q-Bs-HMA][HSO4]4(MIL2),[PPh3-(SO3H)4][HSO4](MIL3),[Bis-BsImB][HSO4]2(MIL4),[Bis-BsMoB][HSO4]2(MIL5) were synthesized use1,4-diazabicyclo [2.2.2]octane,hexamethylenetetramine,triphenyl phosphine,imidazole and morpholine as raw materials, through two or three steps. For polyamine, such as1,4-diazabicyclo [2.2.2]octane and hexamethylenetetramine, two steps were used to alkylation and acidification could obtain the multiple-SO3H ionic liquids MIL1and MIL2; For ordinary amine such as imidazole and morpholine, we should synthesize the dual-core compounds firstly, then synthesize the ionic liquids MIL4and MIL5similar as synthesizing MIL1and MIL2; For triphenyl phosphine, we induce a group of-SO3H through alkylation firstly, then do acidification and sulfonation simultaneously. At last, we obtain a novel ionic liquids MIL3. Through the NMR, FT-IR and Elemental analysis, we insure the structure of ionic liquids we had synthesized. Through the TG-DTG, we investigate the thermal stability of ionic liquids. Through the characterization of UV-visible spectroscopy combined with Hammett method, we determine their acidity.2. Synthesis of Br(?)nsted&Lewis ionic liquidsA series of novel ionic liquids with both Lewis and Br(?)nsted acid sites were synthesized use triethylamine, pyridine, aluminium chloride, ferric chloride, Zinc chloride and cuprous chloride as raw materials, through multiple steps. According to different cation, the ionic liquids were classified into two types:[bPy-SO3H]Cl-FeCl3(XFeCl3=0.3～0.75) and [N(CH3CH2)3-SO3H]Cl-MCly (XMCly=0.67).Through NMR, we ascertain the structure of ionic liquids. Through the FT-IR using pyridine as probe, we investigate the Br(?)nsted-Lewis acidic type of ionic liquids [bPy-SO3H]Cl-FeCl3(XFeCl3=0.3-0.75). The results show that only when the molar fraction of FeCl3is more than0.5, the ionic liquids can have both Br(?)nsted and Lewis acid. Through the FT-IR using acetonitrile as probe, we discussed the relation of different metal chloride and Lewis acidic strength. Through TG, the thermal stability of ionic liquids was also discussed.3. Application of multiple-SO3H ionic liquids as catalyst in acetalization of aldehydes and ketones with diolsThe multiple-SO3H ionic liquids MIL1,MIL4,MIL5,MIL2were used as environmentally benign catalysts for acetalization of different aldehydes and ketones in reflux condition and room temperature respectively. The results show that the ionic liquids were very efficient for the acetalization of diols either in reflux condition or in room temperature. The average yield was above92%using MIL1and MIL4as catalyst at reflux temperature at optimal reaction conditions. When use MIL5and MIL2as catalyst in solvent free system at room temperature, the highest yield is99%using MIL2as catalyst in short time. The results also show that the diols with electron withdrawing substituents can enhanced the rate of acetals formation. UV-visible spectroscopy combined with Hammett method had used to determine the acidity of those ionic liquids and the results are consistent with the order of catalytic activities observed in acetalization reaction. The reusability of catalyst was also investigated, it can be reused at least seven times without obvious activity loss. 4. Application of multiple-SO3H ionic liquids as catalyst in oxathioacetalizationThe conversion of aldehydes or ketones to the corresponding oxathioacetal derivatives were catalyzed by the multiple-SO3H ionic liquids MIL3in solvent free system, at room temperature. The results showed that the novel ionic liquid was very efficient for the reactions with the average yields over90%. Mild reaction conditions, high yields, small amount of usage, operational simplicity, without need of any solvent, wide applicability, and reusability are the key features of this methodology.5. Application of multiple-SO3H ionic liquids as catalyst in Friedel-Crafts reaction1) Alkylation of p-cresol with tert-butanol catalyzed by MIL4The multiple-SO3H ionic liquids MIL4was used as catalyst for alkylation of p-cresol with tert-butanol (TBA) to2-tert-butyl-p-cresol (TBC) in cyclohexane at first time. The optimal reactions are p-cresol (5mmol):TBA:MIL4(molar ratio)=1:1:0.4; cyclohexane3ml;343K;7h. At this condition, the highest conversion of TBA is85.3%and selectivity to TBC is95.2%. Meanwhile, the catalytic activity of this novel ionic liquid was compared with other four traditional ionic liquids. The results showed that IL1has superior catalytic activity to other four traditional ionic liquids. UV-visible spectroscopy combined with Hammett method had also used to determine the acidity of those ionic liquids and the results are consistent with the order of catalytic activities observed in alkylation. Operational simplicity, small amount of usage, high activity, reusability and selectivity are the key features of this methodology.2) Acetylation of alcohols and phenols catalyzed by multiple-SO3H ionic liquidsThree multiple-SO3H functional acidic ionic liquids MIL1, MIL4, MIL5were used as catalysts for the acetylation of acetic anhydride with various alcohols and phenols at room temperature under solvent-free condition. Results showed that all reactions can went smoothly at low temperature in a few minutes, and nearly no by-products. The catalytic reusabilities were also examined, and all mulitiple ionic liquids can be reused at least five times. Compatible with the substrates having other functional groups, fast, high yielding, clean, safe are the key features of this method.6. Application of Br(?)nsted&Lewis ionic liquids as catalyst in Michael addition A series of Br(?)nsted&Lewis ionic liquids[N(CH3CH2)3-SO3H]Cl-FeCl3(XFeCl3>0.5) were used as catalyst for the conjugate addition of various amines to electron deficient alkenes. Through the FT-IR using acetonitrile as probe, we discussed the relation of molar fraction of FeCl3and Lewis acidic strength. Results showed that the Lewis acidic strength rised as the increasing the molar fraction of FeCl3. For michael addition, the ionic liquid[N(CH3CH2)3-SO3H]Cl-FeCl3(XFeCl3=0.67) has the best catalytic activity, the average yield was about90%in several minutes. This method has several key features including operational simplicity, no need of any solvent, low cost of the catalyst used, high yields, reusability, excellent chemoselectivity, and wide applicability.