Study On The Organic Reactions Using PEG As Green Medium

Green chemistry is becoming a central issue in both academic and industrial research in the21st century, and the development of environmentally benign and clean synthetic procedures has become the goal of present day organic synthesis. Organic reactions without the use of harmful organic solvents are now of great interest in organic synthesis.PEG and its monomethyl ethers are inexpensive, thermally stable, recoverable, and nontoxic media for phase-transfer catalysts. PEG, a biologically acceptable polymer used extensively in drug delivery and in bioconjugates as tool for diagnostics, has hitherto not been widely used as a solvent medium but has been used as a support for various transformations. In this dissertation, we studied the green organic reaction by using PEG as the solvent medium, the content and results of the research as following:1. The synthesis of N-substituted imide by using PEG as the solvent medium. Imide derivatives are compounds of considerable interest due to their biological properties and their interest as intermediates in synthesis and in polymer chemistry. Two procedures were used to synthesis these imides:one is the directive condensation by the reactions of succinic anhydrides or phthalic anhydrides with amines;the other one is the substitution by the reaction of nitrogen heterocycles with halides, and both methods were easy-worked with excellent yields and short reaction times respectively, and PEG could be recyclable.2. A directly synthetic method of amides was explored. Amide derivatives are important compounds in organic synthesis and medical industry. They were obtained by directly oxidative of aromatic aldehydes with aromatic amines or aliphatic amines. The best oxidant system (PEG-NaOCl/Bu4NHSO4) was selected from several oxidant systems, the results of the reactions could get considerable yields, the reaction condition was mild and easy to work.3.1,4-Dihydropyridine derivatives exhibit a large range of biological activities. We explored a protocol by using Hantzsch condensation of ethyl (methyl) acetoacetate and aromatic aldehydes in PEG-400with ammonium acetate, this reaction needed not any other catalyst. The results were really excellent, high yields, PEG was recyclable.4. We developed an efficient and green approach to β-amino carbonyl and nitrile compounds which have attracted considerable attention in organic synthesis as to their wide range of biological activities and pharmacological properties. Room temperature Michael additions of various aliphatic and aromatic amines to α, β-unsaturated esters and acrylonitrile to form C-N bond in PEG-400which as a phase transfer solvent was economic, safe, and environment-friendly. Simple experimental procedure, mildness of the conversion, high yields, recyclable.