Synthesis Of Ionic Liquids And Their Applications In Organic Reactions

In recent years, considerable attention has been focused on the use of ionic liquids as novel organic solvents. There are many reports concerning their applications in organic reaction, material chemistry, electrochemistry, polymer chemistry, analytical chemistry and separation technology. Our researches mainly interested in the study of the applications of ionic liquids as new reaction media in Ullmann-type cross coupling reactions, the synthesis of new chiral ionic liquids and their applications in asymmetric reactions. This thesis consists of four main parts:In chapter one, the research progress is reviewed on applications of ionic liquids as novel organic solvents in chemistry, especially in organic synthesis. Based on the data of SCI papers from 1997 to 2006, the basic characteristics of ionic liquids researches in the recent decade are summarized and the trends for their future are also prospected. In addition, three aspects of most important and meaningful applications of ionic liquids in organic synthesis have been briefly discussed.In chapter two, the use of ionic liquids as new reaction media in Ullman-type reactions promoted by amino acids and their derivatives has been studied. A new and efficient method for the copper-catalyzed coupling of imidazoles with vinyl bromides in ionic liquids has been developed. It provides a novel methodology for the highly stereoselective synthesis of N-vinylimidazoles. On the other hand, a method for the synthesis of (Z)-vinyl chalcogenides by the coupling of vinyl bromides with thiols or diphenyl diselenide using copper(I) salts as catalysts in ionic liquids based on amino acids also has been described. The ionic liquids play multiple roles in the reaction: they act as solvent, base, and excellent promoter for the copper-catalyzed coupling reactions. Compared with the previous methods, our copper-catalyzed reactions in ionic liquids have milder reaction conditions, higher reaction yields, and easier product separations. Furthermore, the reaction catalysts and solvents can be recycled and reused.In chapter three, four kinds of new chiral ionic liquids have been synthesized from natural products, such as tartaric acid, lactic acid, amino acids and their derivatives. Their applications in asymmetric reactions have been extensively studied. When the chiral ionic liquids based on dipeptides anion were used as organocatalysts, up to 92%ee were obtained in asymmetric Aldol reaction.In chapter four, a real continuous-flow process for synthesis of alkyl bromides or cyanides was demonstrated by nucleophilic substitution reactions of tosylates with bromide and/or cyanide conducted in ionic liquid. The new process, which the substrate is continuously flowed into the reactor and the product is continuously distilled out at the same time, provides higher reaction yield and shorter reaction time. In perspective, we believe that the real continuous-flow process can significantly contribute towards clean and economically designed chemical engineering.