Study On Metal-Free Cyclization Of Thiadiazoles And Triazoles Heterocyclic Compounds

Nitrogen-containing compounds are a very important part of the entire heterocyclic structure.They are widely found in nature and can be used as the key skeleton center of many drug molecules.Due to the structural and property characteristics of 1,2,3-thiadiazole and 1,3,4-thiadiazole,various derivatives obtained after modification and functionalization of thiadiazole can be obtained in many fields applications.In recent years,due to its unique biological activity and pharmacological properties,many chemists have focused their research on applying it to anti-cancer,anti-tuberculosis,anti-fungal and other drug molecules.And the research of such compounds in agriculture has been receiving attention,such as the application of pesticides and herbicides.In addition,thiadiazole compounds also have many photoelectric properties and can be used in organic photovoltaic cells,solar sensitized cells and organic transistors.Triazole compounds are also nitrogen-containing five-membered heterocyclic compounds.They contain three nitrogen atoms and a hydrogen atom is attached to one of them.Therefore,it can be modified and functionalized to obtain various derivatives which show unique properties,such as medicine,agriculture,materials science,and photoelectric properties.They can be used not only as inhibitors of novel alkaloids and enzymes,but also as fluorescent probes and applied to various polymer materials.The first chapter of the thesis summarizes the introduction,biological activity,pharmacological properties and photoelectric properties of thiadiazole and triazole compounds.It also briefly describes the development of the synthesis of thiadiazole and triazole compounds in recent years.The meaning of topic selection and design ideas are also described.The second chapter reported a kind of aldehyde thiosemicarbazone as a substrate,and intramolecular cyclization under the action of high-valent iodine acetate iodobenzene to obtain 2-amino-1,3,4-thiadiazole and its derivatives.Compared with previous methods,the reaction avoids the use of transition metals,the substrate is easier to prepare and the reaction steps are simple and the yield is higher.Chapter 3 developed a [4+1] cyclization reaction with N-p-toluenesulfonyl hydrazone acetophenone and ammonium thiocyanate as substrates,mediated by elemental iodine to obtain 1,2,3-thiadiazole compounds.The method we propose can carry out the reaction at room temperature without metal catalysis,and the solvent used is also more environmental friendly and has good substrate universality.We also conducted two derivatization experiments of palladium-catalyzed coupling reactions according to the characteristics of the products,and they also had good yields in the gram-level reaction,and the reaction mechanism was improved through control experiments.In Chapter 4,we proposed a method to use N-p-toluenesulfonylhydrazine acetophenone and N-p-toluenesulfonamide as reaction substrates,avoiding the use of azide-type chemicals with higher risks.Under alkaline conditions achieve intermolecular [4+1] cyclization reaction.Compared with traditional methods,we use different nitrogen sources to obtain the target product by removing the Ts group of two molecules.