Study On The Synthesis Of Some Heterocyclic Compounds In PEG-400

Heterocyclic compounds, especially imidazoles, 1,4-dihydropyridines and 4H-pyrans have a wide range of biological and pharmacological activities. Heterocyclic compounds and their derivatives as intermediates of pesticides, pharmaceuticals, dyes and other fine chemical products have already been widely applied. Scientists around the world very concerned about the synthesis of these compounds.Low-molecular-weight polyethylene glycol PEG-400 is a common liquid oligomer, it is low-toxic, easily degradable, non-volatile, non-combustible and inexpensive. PEG-400 has a good solubility for most organic and metal organic compounds, moreover,which was stable in acid and alkali condition, oxidation system of O2 and H2O2, redox system of NaBH4. PEG-400 as a new reaction medium has begun to attract more attention. The dissertation focuses on the synthesis of 2,4,5-trisubstitued imidazoles and 1,2,4,5-tetrasubstitued imidazoles, 1,4-dihydropyridines and 4H-pyrans using PEG-400 as reaction medium without any catalyst. The thesis is mainly divided into four chapters:Chapter one: the progress of studies on the synthesis of imidazoles, 1,4-dihydropyridines and 4H-pyrans, the application of PEG-400 as reaction medium in the organic synthesis in recent years are reviewed.Chapter two: a series of 2,4,5-triaryl-1H-imidazoles were synthesized by three-component condensation of aldehydes, benzil and ammonium acetate in PEG-400 at 110 oC; 1,2,4,5-Tetraarylimidazoles were also synthesized via four-component condensation of aldehydes, benzyl, ammonium acetate and aromatic primary amines in PEG-400 at 110 oC.Chapter three: various of 1,4-dihydropyridines were obtained by the reaction of aldehydes, ethyl acetoacetate or acetylacetone, ammonium acetate using PEG-400 as reaction medium without catalyst.Chapter four: an efficient three-component synthesis of 4H-pyrans by the reaction of aldehydes, ethyl acetoacetate or acetylacetone and malonitrile were described.This method has the advantages of easy work-up, less pollution and environmentally friendly procedure. We obtained the optimum reaction conditions by studing the factors respectively which affect the reactions such as the ratio of raw materials, reaction medium, temperature and time. The structures of all compounds were confirmed by IR, 1H NMR, 13C NMR and Elemental analysis.