Study On The Application Of Polyethylene Glycol In Aldimine Condensation And Alcohol Oxidation

Recently, the applied research of PEG has received more attention in the field of green chemistry. PEG has many favorable properties such as low-cost, good solubility, excellent reusability and environmentally friendly properties. PEG has been successfully applied to many areas of organic chemistry. Liquid PEGs with low molecular weight act as a new type of organic solvent alternatives. Meanwhile, the solid PEGs with high molecular weight have been received more attention and studied by chemists as one of several first developed carriers. In this paper, we conduct systematic applications study of polyethylene glycol as solvent and catalyst supports in amine-aldehyde condensation reaction and the oxidation reaction of alcohol with a view to develop some new environment-friendly methods, and the research contents include the following aspects.A simple and environmentally friendly method for synthesis of benzimidazole has been developed. The study found that when the organic substrate is performed in an amount of 20 mol% Fe3O4, the yield was above 80%. Nano-Fe3O4 catalyst could be effectively stabilized by polyethylene glycol molecular and easily be recycled with the catalytic activity remaines unchanged. Compared with the existing technology, this method has many advantages, such as mild reaction conditions, simple operation which is in line with the direction of development of green chemistry and has broad application prospects.An efficient and environmentally friendly procedure for synthesis of benzimidazoles has been developed, which was catalyzed in PEG1000-DIL/toluene temperature-dependent biphasic system. It was found that this catalytic system has broad scope and high catalytic efficiency, and the reaction gave above 75% yields when it was performed with an amount of 10 mol% FeCl3 and the reaction temperature of 80℃. Also, the imidazole group could effectively enhance the catalytic performance of FeCl3. This procedure include many advantages such as simplicity of operation, easy isolation of products and excellent resubility with high catalytic activity after reused for five times.An efficient procedure for preparation of gold nanoparticles using PEG as template and stabilizer was developed to investigate the effect of selective oxidation reactions of alcohol in the aqueous phase using H2O2 as green oxidant. The study found that the prepared gold nanoparticles has high catalytic activity for selective oxidation of alcohols and TEM characterization found that the gold nanoparticles has smaller size and more consistent shape. Nano-Au/H2O2 system for oxidation of alcohol has good scope and high catalytic efficiency, particularly for the oxidation of fatty alcohols. The prepared nano-Au remains has good stability and catalytic activity after six runs as relatively fresh catalyst.A new heteropolyacid catalyst supported in long-chain ionic liquid with surface active properties was preparared and an efficient catalytic system with H2O2/PEO@IL-HPW has been studied for selective oxidation of alcohols. The outstanding advantage of this process is that the catalytic system could be applied to a variety of o alcohols with high selectivity. Meanwhile, the catalytic system has good cycling performance after repeated recycling and conversion and yield have no significant decline.A simple and efficient PEG1000-DAIL/TEMPO/TBN catalytic oxidation system for selective oxidation of alcohols with molecular oxygen was developed. The alcohols including benzyl alcohol, allyl alcohol and heterocyclic alcohol could be effectively converted to the corresponding series of aldehydes or ketones. The catalystic system could be easily recycled with good repeated performance. Also, the catalytic mechanism was discussed with the reaction channels through a nitrogen carbonyl cation.A new TEMPO functionalized PEG-ILs was prepared and a simple and efficient oxidation system with CuCl、AuCl3 and CAN as catalysts have been developed for the selective oxidation of alcohols. The oxidation system was capable of catalyzing the selective oxidation of a series of alcohols to the corresponding aldehydes or ketones. The catalyst system can be easily recycled with good reusability. The method is simple, mild and in line with the direction of development of green chemistry.