Synthesis And Study Of The Functional 2, 5-disubstituted 1, 3, 4-oxadiazoles

Recently, the study of heterocyclic compounds have attracted attention in pesticide and medicine chemistry, because of their biological activities, such as antimicrobial, insecticides, herbicides, plant-growth regulators, antivirus and so on. Meanwhile, many of novel and green synthesis methods which made advantageousness in the synthesis of heterocyclic compounds due to not only decrease cost but also increase the yields have being used. The result have been conformed in the article.This paper is divided into six chapters.Chapter one 2,5-disubstituted-1,3,4-oxadiazoles are widely used in the industry of medicine and material because of their wide biological activities. The new methods, new reagents and new technologies, such as polymer supported organic synthesis, microwave irradiation and solventfree reaction, of synthesis of 2,5-disubstituted 1,3,4-oxadiazoles are reviewed in this chapter.Chapter two the required intermediate of 2-chloromethylene-5-(2-benzofuran) -1,3,4-oxadiazoles is prepared by the reaction of 2-benzofuroyl hydrazines with chloroacetic acid in the presence of phosphorus oxychloride under microwave irradiation. Treament of this componuds with arylamine or sodium phenoxide in the presence of sodium hydroxide in ethanol solvent under microwave irradiation affords 2-substituted -5-(2-benzoruran)-1,3,4-oxadiazoles and in good yields. We also studied different affects of varies conditions (ratios, solvent, irradiation power and time) on the reactions.Chapter three we studied the method for the synthesis of 2-substituted -5-(2-benzoruran)-1,3,4-oxadiazoles under microwave irradiation in solvent-free condition.Chapter four A series of substituted 1,3,4-oxadiazoles are synthesized by cyclization of several acids with 2-benzofuroyl hydrazines under the solvent-free and microwave irradiation conditions. We studied different affects of varies conditions (ratios, solvent, irradiation power and time) on the reactions. Then we synthesized 18 new2,5-disubstituted 1,3,4-oxadiazoles.Chapter five Summarized the methods of the synthesis of 1,3,4-oxadiazolines, and their biological activities in pesticides and medicines.Chapter six Many scientists are making great efforts to study the biological activities of oxadiazolines in order to found the better medicine which is more beneficial to people. The reaction of 2-benzofuroyl hydrazines with arylaldehydes gave the corresponding hydrazones. Then these compounds respectively cyclodehydrated with acetic anhydride to afford seven new 1,3,4- oxadiazolines.The structures of all compounds were confirmed by elemental analyses, IR and H¹NMR and ¹³CNMR. Compared with conventional methods, the conditions of these reactions are mild and the procedures of separation and purification of the desirable compounds are simple.