Syntheses Of Guanidine And Guanidinium Ionic Liquids And Their Applications In Suzuki Reaction And Aminolysts Of Epoxides

Transition metal catalyzed carbon-carbon coupling reaction is currently the mostimportant reactions in organic chemistry, and it is one of the primary means ofsynthesis of complex molecules. And, palladium-catalyzed Suzuki coupling reactionof benzene boronic acid and halogenated aromatics have the following advantages:mild reaction conditions,low toxicity and high stability of organic boron reagents,broad applicable scope of substrate,simple of reaction condition,no subsidiaryproduct,easy to handle of the product,so that the reactions take an important positionin the carbon-carbon coupling reactions. And it is an effective method of the synthesisof biphenyl compounds. It is widely used in the synthesis of natural products,pharmaceutical intermediates and functional materials.Suzuki coupling reaction is an important method for the formation ofcarbon-carbon bond, especially for the coupling of biphenyl. This papersummarizes the basic elements of Suzuki coupling reaction, and sums up itsdevelopment in the green media. Suzuki coupling reaction is a kind of C-C bondcoupling reaction of aromatic boric acid and aromatic halogenated hydrocarbons,which produces aromatic couple compounds with the transition metal Pd (0) or Ni ascatalyst.It is one of the important methods in organic synthesis.Because of the importance of the Suzuki coupling reaction, it is widelyresearched. And present research is always towards green, economy, environmentalprotection, recycling and other direction. Because of the low solubility of thesubstrate, and the difficulty of looking for the water-soluble ligand, Suzuki couplingreaction in the water has great limitations. Ionic liquids is a kind of green reactivemedia, and it is reusable, etc, so it is widely researched in recent years.Palladium-catalyzed Suzuki reaction has been carried out in a number of ionicliquids, including imidazole-based ionic liquids and other quaternary ammoniumsalts,quaternary phosphonium salt ionic liquids, and have already made goodprogress in it. Polyethylene glycol (PEG) as a non-toxic, recyclable, easy to get andcheap green media or liquid carrier, has gradually draw the attention of the organic field. PEG can serve as a solvent for accelerating reaction, and also as a carrier forfixing catalyst to reduce the loss of the catalyst in the Suzuki reaction process, so it isvery popular with chemists. The physical properties of Supercritical carbon dioxide(scCO₂) can be controlled by changing the temperature and pressure, that make itpossible to separate the catalyst and the reaction products, simply andconveniently.Also the scCO₂has low viscosity and high diffusivity, that is helpful tothe transfer of the materials and energy, which can prompt the reactions to show ahigher rate in supercritical conditions.Compared with the aromatic bromides and aromatics iodides, which have highactivity, the chlorinated aromatic is cheaper and easier to get. But because of the lowreactivity of chlorine atoms, the application in organic synthesis of chlorinatedaromatic is limited. However, from industrial point of view, using chlorobenzene assubstrate, which is cheap and easy to get, is the direction of development of thecoupling reaction. Since the1990s, through the appropriate modification of palladiumcatalyst or selecting appropriate ligand, to get highly active palladium catalyst, wecan achieve the coupling reaction of aryl chlorides. Compared with conventionalheating, microwave heating has the advantage of faster, higher thermal efficiency,energy conservation, clean, simple operation and so on. So, it has become animportant tool in organic synthesis. Supported catalysts can be well separated andreused, so the organic chemists pay more and more attention to it. And it is now oneof the directions of development of chemistry. The materials of the carrier ofpalladium catalyst in Suzuki coupling reaction include: active carbon, metal oxides,porous aluminosilicate molecular sieves, materials of silicon dioxide, active clay,polymer and so on. There are two main methods of the preparation of the Supportedpalladium catalyst. One is adsorbing the palladium to the surface of the carrier. Theother is grafting special functional groups to the surface of the carrier, and thenembarking the palladium on the functional group by way of coordination.As our research team has been study in the synthesis and application ofguanidine, guanidine salt and guanidine salt ionic liquids, and alkyl guanidine is agood ligand of Pd catalyst. Tetra methyl guanidine coordinated palladium catalystsystem catalyzed Heck reaction well. In this paper, the Suzuki coupling reactionswhich is catalyzed by the alkyl guanidine coordinated palladium catalyst system hasbeen studied. The experimental results show that guanidine coordinated palladium catalystsystem can catalyze Suzuki coupling reactions, and this is an efficient and stablecatalytic system against air and water. And this opened up new ways ofnon-phosphorus catalyst. Through the study of Suzuki coupling reaction which iscatalyzed by the guanidine coordinated palladium catalyst system,we found that, first,pent alkyl guanidine is the better ligand than the tetra alkyl guanidine, second,water-ethanol is an ideal choice of solvent, the last,we can use potassium carbonate as thebase. Such a catalyst system can be carried out at room temperature,and can alsocatalyze coupling of aryl chlorides. During the coupling of benzoboric acid andp-nitro-iodobenzene, the value of TON can be up to850000. In the expansion of thecoupling reaction we found that the catalytic system does not require the protection ofinert gas, and its expand to functional groups is very good, and it can catalyze thecoupling reactions of these functional groups, such as substrate material with-CHO,-COCH₃,-COOC₂H₅,-OCH₃,-CN,-NO₂,-F and so on.The third part is the use of previously synthesized guanidinium salt, and AlCl₃,ZnCl₂, SnCl₂prepared three kinds of Lewis acidic guanidinium ionic liquids(LAGILs), both the Lewis acid and ionic liquid. The advantage is its application toaminolysis of epoxide reaction. In the study, we selected catalyst3c,5mol%in theamount of catalyst used, catalyzed epoxide ring opening reaction, showing goodcatalytic activity, short reaction time, high yields. At the same time compared to othercatalysts in the literature, catalyst3c shows better catalytic activity, but the catalyticselectivity to be improved. Five times in the reuse the catalyst3c, the activity andselectivity did not change much.This paper developed a new catalytic system: at room temperature without inertgas protection, water-ethanol system, the pent alkyl guanidine coordinated palladiumcatalyst system can be a good coupling reaction catalyzed Suzuki, but not functionalgroup Restrictions. Also developed a new, effective and reusable Lewis acidguanidinium ionic liquid catalyst system, under the conditions used for solvent-freeepoxide aminolysis reaction, reaction rate, high yield, selection Good, product easy toseparate the ionic liquid can be reused.