Studies On Syntheses, Properties And Applications Of Vilsmeier Salts And Guanidinium Ionic Liquids

Room-temperature ionic liquids (RTILs) are defined as salts that melt below room temperature. RTILs are composed of a cation and an anion, whose forces of attraction are not sufficiently strong to hold them together as a solid at ambient temperature, and therefore these salts are liquids, unlike traditional molten salts such as for instance sodium chloride that melts above 800°C. RTIL's are organic fluids typically containing nitrogen-based organic cations and inorganic anions. This property allows them to dissolve organic compounds and serve as potential solvents for industrially important organic reactions. They are emerging as a novel replacement for volatile organic compounds traditionally used as industrial solvents. RTIL's might be a good possibility for helping create"greener"chemistry, since there are any ways of combining ions to make them. This has been referred to as'designing'thesolvent system for a particular reaction process, which could result in unique product selectivities or even new chemistry compared to the traditional solvents.The RTILs show useful properties such as thermal stability, high ionic conductivity, negligible vapor pressure and large electrochemical window. The RTILs emerged as an alternative recyclable environmentally benign reaction media for chemical process including bio and chemical catalysis.The physical and chemical properties of RTILs, often defined as"green solvents and designed solvents",can indeed varied over a wide range by selection of suitable cations and anions.The most common RTILs in use are salts with N-alkylpyridinum and N,N- dialkylimidazolium cations, such as [Bmim][PF6] (1- butyl -3-Methylimidazolium hexafluorophosphate) and [Bmim][BF4] (1-butyl-3-methylimidazolium tetrafluoroborate). At present,in order to substitute toxic,harmful organic solvents and develop highly efficient green chemistry process,to develop synthesis and application of RTIL,especially, as solvents and catalysts have received much attention. There are several advantages and reasons for synthesizing alkylguanidinium- based ionic liquids: 1. The positive charge in the guanidinium salts is delocalized over one carbon and three nitrogen atoms, which gives them a high degree of thermal stability compared to tetraalkylammonium salts. 2. The alkyl- guanidinium salts are widely used as phase transfer catalyst due to their exceptional stability at high temperature. 3. Alkylguanidinium salts exhibit some particularities due to its extraordinary bulkiness. For example, the literature reports structural features, which support the existence of an electron-deficient state at the central carbon atom surrounde by the three nitrogen atoms.N, N, N', N'-tetramethylchloroformamidinium chloride (Vilsmeier salt), is prepared through the reaction between 1,1,3,3-tetramethylurea and POCl3 under the mild condition. It is an efficient dehydration reagent, but also the intermediate of the preparation of guanidinium ionic liquids. Owing to the similar framework of Vilsmeier reagent, Vilsmeier salt has also been tried in organic reactions.Developments of new basic reactions and new synthetic methods are the basis for the innovation and advance of organic chemistry. Based on the research achievement of our group in room temperature guanidinium ionic liquids, my thesis starts from the design and synthesis of room temperature guanidinium ionic liquids, aming to develop new basic reactions and new synthetic methods for task functional ionic liquids, particularly, developing a new synthetic strategy to provide a general and simple route to polysubstituted six-membered ring systems. At the same time, starting from the N, N, N', N'-tetramethylchloroformamidinium chloride (Vilsmeier salt), investigations were also carried out on the synthetic methodology for six-membered oxygen-, and nitrogen-containing heterocycles by intermolecular addition. The contents in this thesis mainly include two parts and five aspects.Knoevenagel reactions could occur in high polar solvents, such as DMF or DMSO, and ionic liquids, which are absolutely made up of anions and cations, can also be considered as high polar solvents, so Knoevenagel reactions in ionic liquids have been paid more attentions. In the recent years, different ionic liquids, different catalysts, different kinds of reagents have been tried to develop Knoevenagel reactions. As a reaction medium, cyclic guanidinium lactate ionic liquid can catalyze the Knoevenagel condensation of one of aromatic aldehydes with each of active methylene compounds at room temperature in a high yield of over 90% within just 1–7 min. At the same time, the work-up procedure is very simple and the products are not needed to be further purified. The ionic liquid can be easily reused without activity loss.Carbon-carbon bond formation and transformation of functional group are the most important and basic reactions to contribute the skeleton of carbon construction. Base on our study about Knoevenagel and Michael reactions in guanidinium lactate ionic liquids, we developed a new method to syntheses polysubstituted benzenes through tandem Knoevenagel and Michael reactions in one pot reactions in guanidinium lactatic ionic liquids.Six-member N-heterocycles exist widely in nature products as a key structure cell, and they are also useful intermediates in organic synthesis. The vast number of bioactive natural products and pharmaceutical drugs based on the pyridin-2(1H) -one ring system, such as elfamycin and ilicolicin, has become very important in the area of natural product and pharmacetical chemistry. In addition, functionalized pyridin-2(1H)-ones have been used as versatile intermediates in the synthesis of a wide range of nitrogen-containing heterocycles, such as pyridine, piperidine, quinolizidine, and indolizidine alkaloids. Because of the similar structures between N, N, N', N'-tetramethylchloroformamidinium chloride (Vilsmeier salt) and Vilsmeier reagent, we syntheses pyridin-2(1H)-ones by using Vilsmeier salt andα-Oxo amides, and so obtained two intermediate, 2H-pyran and 4H-pyran.