Studies On Synthesis And AHerbicidal Activity Of Triazolo [3,4-b] Thiadiazole Derivates

Recently,1,2,4-Triazole derivatives are known to exhibit antibacterial, antifungal,antitubercular,anticancer, anticonvulsant, anti-inflammatory, analgesic, and molluscic-idal properties, therefore, the compounds bearing triazole ring in general andcondensed heterocycles in particular are the topic of many investigation. A survey ofliterature revealed that substituted-1,2,4-triazolo-[3,4-b]-1,3,4-thiadiazole rings haveattracted the interest of pharmaceutical companies recently. This is due, in part, to thewide range of biological activities associated with this heterocyclic scaffold. Somederivatives of them have shown significant biological properties, such asantimicrobial, antibacterial, antitubercular, anti-inflammatory, and antifungail. Owingto3-aryl-4-amino-2,4-dihydro-1,2,4-triazole-5-thione was one of the key organicsynthesis intermediate, it has been applied on triazolo condensed heterocycliccompounds generally.In this dissertation, I would like to report on the synthesis of3,6-disubstituted1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles via a tandem aza-wittig reaction in satisfactoryyields. Presumberly, the conversion of the title compounds involves initial aza-Wittigreaction between the iminophosphorane and the phenylisocyanate to givecarbodiimide as a highly reactive intermediate, which easily undergoes ring closureacross the mercapto group to give the otherwise not readily available3-aryl-6-arylam-ino-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole. Besides, in the chapter three, theintroduction of fluorine at3-position of phenyl into triazolothiadiazole scaffold, westudy on the spectral characters and herbicidal activities of the synthesizedcompounds. In the chapter five, with the aim of investigating the spectra proprerities,herbicidal activities, and reaction regularity of acidamide compounds, we haveintroduced N-aryloxyacetyl and N-benzoyl into triazolothiadiazole scaffold.1、The specific research contents as following:Ⅰ3-aryl-6-arylamino-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles.Ⅱ3-(4-fluorophenyl)-6-arylamino-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles.Ⅲ3-aryl-6-N-substitutedphenoxyacetyl-N-(4-fluorophenyl)-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazoles.Ⅳ3-aryl-6-N-substituted(hetero)arylformyl-N-(4-fluorophenyl)-1,2,4-triazolo[3,4-b ]-1,3,4-thiadiazoles.2、The prediminary herbicidal activity of the new compounds mentioned weremeasured, according to the experiment, some compounds possessed high herbicidalactivities to the dicotyledonous weeds and monocotyledonous weeds.