Extended Research On The Applications Of Ionic Liquids In Organic Synthesis

Currently, a major drive is underway in academia and industry to substitute more environmentally friendly technologies for traditional ones in which damaging catalysts and volatile organic solvents are heavily used. Room temperature ionic liquid (RTIL, called IL for short) are considered as environmentally benign solvents, not only because of their low vapor pressures, but more importantly, also because of their ability to act as catalysts. Moreover, RTILs have several other attractive properties, including chemical and thermal stability, nonflammability, high ionic conductivity, and a wide electrochemical potential window. Recent years, ILs have been widely used as catalysts and solvents in organic synthesis, but those researches of application in the synthesis of aspirin, aromatic amines and sulbactam acid were hardly reported. On the other hand,the traditional technology for the three kind of syntheses, using organic reagent and inorganic acid as solvent or catalyst, which inevitably brought on serious environmental pollution and equipment corrosion,but instead,those problems can be solved by introducing ionic liquids as solvent or catalyst applied to the reaction. Therefore, further extended researches of ILs in organic synthesis have great significance and application values. This dissertation includes the three following aspects:1. Research on the application of ILs in synthesis of AspirinSynthesis of Aspirin can be carried out in sulfuric acid, however, having some shortcomings, such as:the existence of many side reactions, corrosion of equipment and environmental pollution and etc. In this paper the synthesis of aspirin was investigated in 5 kinds of ionic liquids 1,3-dialkylimidazolium. The effects of reaction time and ratio of acid to alcohol on the reaction were examined. Experimental results showed that ionic liquid [bmim]Br could be used as a catalyst of aspirin. The optimized estefification conditions were:(n)salicylic acid:(n)acetic anhydride=1:2, catalyst 2 mL, reaction temperature 80-85℃, reaction time 3 h. The yield of esterification could reach 81.6%. The isolation of desired products could be achieved via simple decantation and the ILs can be reused five times without significant decrease of its catalytic activity. 2. Research on the application of ILs in synthesis of aromatic amineSynthesis of aromatic amine can be carried out in organic solvents, such as formic acid, acetic acid, dichloroethane and other organic solvents, which have some shortcomings:a long reaction time, a large amount of hydrazine hydrate, and serious environmental pollution and etc. In this paper, by employing 5 kinds of Brφnsted acidic ionic liquids as the reaction solvent, the reduction of nitrobenzene to aniline in the presence of hydrazine hydrate catalyzed by Y-alumina can be achieved.The effects of reaction time, temperature and amount of hydrazine hydrate and catalyst on the reaction were also examined. Experimental results showed that the optimized reduction conditions were:(n) nitrobenzene:(n) hydrazine hydrate=1:1.9, catalyst 0.3 g, reaction temperature 80℃. reaction time 1h. The yield of reduction could reach 96.0%. This study identified several advantages of the reaction carried out in ionic liquids, namely:1)shorter reaction time,milder conditions,satisfied yield; 2) higher catalyst distribution in the ionic liquids,exerted a strong influence on catalytic activity; 3)lower concentration of hydrazine hydrate, eased the cost.3. Research on the application of ILs in synthesis of Sulbactam acidSulbactam acid synthesis can be carried out in organic phases of ethyl acetate or methylene chloride with using sulfuric acid as the catalyst and solvent, which have some shortcomings, such as:the existence of low yield, and serious corrosion and pollution. In this paper, by employing 3 kinds of Brφnsted acidic ionic liquids both as the reaction solvent and catalyst, hydrazine hydrate as the hydrogen source,cast iron as the electron transfer agent of the environment, the synthesis of Sulbactam acid can be achieved. The effects of reaction time, temperature and amount of hydrazine hydrate and cast iron powder on the reaction were also examined. Experimental results showed that the optimized reduction conditions were:The optimized conditions were:n(dibromo penicillin sulfoxide acid):n(hydrazine hydrate):n(cast iron powder)=1:10:4.5, reaction temperature 25℃, reaction time 4 h, the yield obtained 87.0% at most. The study identified several advantages, such as:milder conditions, satisfied yield, no serious corrosion and pollution. Therefore, it provided a new approach for the preparation of halogen-containing compounds synthesized through dehalogenation, and also for the management of wastewater pollution of aromatic halides, a theoretical and practical value of the new approach.