Studies On The Synthesis Of 2, 5-Disubs Tituted 1, 3, 4-Oxadiazolines And Oxadiazoles

Oxadiazolines and oxadiazoles are useful compounds in the pharmaceutical,agricultural and material fields.They have some important bioactivities and optical activities,such as anti-inflammatory,antibacterial, regulating growth of plants,killing pest,electroluminescent etc.In this thesis,the perchloronictinic hydrazine was obtained from successive esterification and hydrazinolysis of perchloropyridin-2-carboxylic acid.the hydrazine is condensated with aldehydes（ketones） to produce corresponding hydrazones in mild condition with high yield.At last,the products of 2-substituted-5-（perchloropyridin-2-yl）-1,3,4-oxadiazolines and 2-substituted-5-（perchloropyridin-2-yl）-1,3,4-oxadiazoles have been obtained by the cyclodehydration of these hydrazones in acetic anhydride.The results are as follows:（1）Perchloronictinic hydrazine is synthesized in mild condition with 86%yields.The experimental condition is optimized.（2）Thirteen new oxadiazolines and four new oxadiazoles were synthesized by cyclization of hydrazones in acetic anhydride,and their structures were determined with elemental analyses,¹H NMR spectra,¹³C NMR spectra,IR spectra and Ms spectra.（3）The cyclodehydration of 4-chlorobenzylidene-perchloronicotinic acid methylhydrazone in acetic anhydride is studied.It is indicated that the oxadiazoline as a main product was obtained at about 100℃and the oxadiazole as a main product when refluxing at 120℃in this reaction. There weren’t papers covering cyclization of hydrazones in acetic anhydride to obtain 1,3,4-oxadiazoles.And we also studied the conversion between the oxadiazoline and oxadiazole.It is indicated that the oxadiazole could be obtained from the oxadiazoline with low conversion（about 53%） at 120℃.