Ionic Liquids Catalyzed Conversion Of Carbon Dioxide To Fine Chemicals

CO2 is a main greenhouse gas which causes global warming. On the other hand, CO2 is one of the most economic, non-toxic and renewable Cl feedstocks. The use of abundant CO2 resource is in line with the requirement of green chemistry, which is attracting many attentions from scientists. Eco-friendly ionic liquids exhibit unique advantages for capture and transformation of CO2, due to their excellent properties including negligible vapor pressure, tunable structure and good solubility. This dissertation focuses on ionic liquid catalyzed conversion of CO2 to high value-added fine chemicals. Novel synthetic routes have been developed to fully utilize CO2 resource and avoid drawbacks in traditional synthetic routes, such as using toxic materials, tedious procedures or harsh reaction conditions. The main results are as follows:1. Binary Ionic liquids Synergistic Catalysts for Conversion of CO2, Ethylene Oxide and Amines to 3-Aryl-2-oxazolidinonesA novel method for the conversion of CO2, ethylene oxide and amines to 3-aryl-2-oxazolidinones and ethylene glycol has been developed. This method consists of two parallel reactions and a subsequent cascade reaction between the two products of the corresponding parallel reactions. Ethylene oxide as a high-energy molecule is used to fix CO2 to ethylene carbonate. Meanwhile ethylene oxide reacts with aniline to form the intermediate 2-(phenylamino)ethanol. Then,2-(phenylamino)ethanol reacts with ethylene carbonate to yield 3-phenyl-2-oxazolidinone and ethylene glycol. Notably, the binary ionic liquids of 1-buty 1-3-methyl-imidazolium bromide (BmimBr) and 1-buty 1-3-methyl-imidazolium acetate (BmimOAc) demonstrate a synergistic catalytic effect on this new strategy. BmimBr is essential in two parallel reactions owing to the good nucleophilicity and leaving ability of bromide, and BmimOAc plays a dominant role in the subsequent cascade reaction owing to the strong basicity of acetate. In addition, the binary ionic liquids can be used three times without significant loss of catalytic activity.2. DBU and DBU-Derived Ionic liquid Synergistic Catalysis for the Conversion of CO2 to 3-Aryl-2-oxazolidinonesAn intermolecular synergistic catalytic combination of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and a DBU-derived bromide ionic liquid HDBUBr has been developed for the conversion of CO2, epoxides and amines. Various 3-aryl-2-oxazolidinones are produced in moderate to excellent yields under metal-and solvent-free conditions within a short reaction time. NMR spectroscopy and DFT calculations demonstrate that DBU as a hydrogen bond acceptor and the HDBUBr as a hydrogen bond donor activate the substrates cooperatively by inducing hydrogen bonds to promote the reaction effectively. Based on these results, a possible reaction mechanism on the synergistic cataly sis of DBU and HDBUBr is proposed.3. Ionic liquids Catalyzed "One-Pot Multi-Step" Conversion of CO2 to 5-S ubstituted-3-aryl-2-oxazolidinonesWe have developed a method for ionic liquid catalyzed "one-pot multi-step" reaction of CO2 with epoxides, amines without separation of intermediate cyclic carbonates to synthesize 5-substituted-3-aryl-2-oxazolidinones. Different ionic liquids have been investigated as catalysts. Upon using BmimOAc, the "one-pot multi-step" reaction of CO2, propylene oxide and aniline affords 5-methyl-3-phenyl-2-oxazolidinone in a yield of> 99%. When usinga mixture of BmimOAc and BmimBr, the reaction gives desired product in the yield of >90% under the condition of lower catalysts amount. Additionally, the ionic liquids can be used three times without significant loss of catalytic activity. This study opens an avenue for synthesis of more complex 5-substituted-3-aryl-2-oxazolidinones directly from CO2.4. Ionic liquids Catalyzed Conversion of CS2, Ethylene Trithiocarbonate to [l,3]Dithiolan-2-ylidene-arylamineA novel method for the conversion of CS2, ethylene oxide and amine to [l,3]dithiolan-2-ylidene-arylamine has been developed. Under optimized reaction conditions, the product is obtained in a moderate yield. A reaction course is proposed for the generation of [1,3]dithiolan-2-ylidene-phenylamine. CS2 reacts with ethylene oxide viathe formation of an intermediate 153-oxathiolane-2-thione to afford ethylene trithiocarbonate, followed by reaction of ethylene trithiocarbonate with aniline giving the desired product. Subsequently, we have investigated the preparation of [l,3]dithiolan-2-ylidene-phenylamine from ethylene trithiocarbonate and aniline. Acetate ionic liquids exhibit good catalytic activity for the reaction, which the yields of product are>85%. And BmimOAc can catalyze conversion of various aromatic amines to corresponding [1,3]dithiolan-2-ylidene-arylamines smoothly.5. Ionic liquid Catalyzed One-Pot Reaction of CO2, Epichlorohydrin and Amines to Synthesize 4-(AryIamino)methyl-ethylene carbonateIonic liquids are firstly used as catalysts for one-pot synthesis of amino functionalized cyclic carbonates from CO2, epichlorohydrin and amines. The catalytic activity of catalysts is affected by the anions of ionic liquids, and follows the order of Cl"> Br’> OAc"> BF4"> PF6". In addition, the effects of the ratio of epichlorohydrin and aniline, ionic liquid amount, reaction temperature, reaction time and CO2 pressure are investigated. Under optimized reaction conditions,4-(phenylamino)methyl-ethylene carbonate is generated in a moderate yield. And a possible reaction mechanism is proposed based on the reaction results.