الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
4-thiadiazole was synthesized via sulfuration of corresponding acylhydrazines: 1 4-dicarbonyl or acyl precursors using phosphorus sulfide reagents such as P2S5 and Lawesson’s reagent (LR) [20]. This method involved aggressive conditions or stoichiometric formation of unacceptable byproduct. 1, 3, 4-Thiadiazoles derivatives prepared from carboxylic acids hydrazide using propyl phosphonic anhydride (T3P), (Scheme Ⅰ.2). T3P acts as both a coupling and a cyclo dehydration agent. The reaction afforded multifunctional functional thiadiazole contaminated with trace percentage (%) of 1, 3, 4-oxadiazole byproductIn aqueous solution Et3N, isothiocyanate 13 and acid hydrazide 14 react giving 2- substituted-1, 3, 4-thiadiazole 15 [27]. Using dithiocarbamates 18 and acid hydrazides, 5 substituted-2-amino-thiadiazoles 17 obtained in good yields at the same conditions. Through thionation with LR, P2S5, and H2S/HCl, acylhydrazine produced thioacylhydrazides Diacylhydrazins generated from acyl hydrazines. P2S5 and LR used in cyclization N, Ndiacylhydrazines in DMF, DCM, THF, dioxane, and toluene. Indolyl-thiadiazoles produced via oxidative cyclization of diacylhydrazine 18 with LR reagent in presence of THF, toluene dioxane, and xylene. Thiohydrazine derivatives cycled yeild many bioactive reactive 1, 3, and 4-thiadiazoles. Thiosemicarbazide (TSC) derivatives produced during cyclization include 2- NH2-thiadiazoles. In the presence ofdehydrating agent such as EDCI, DCC, TMSCl, TsCl PPh3, SOCl2, PCl5, or di-Ph-Cl-phosphate and acylation, Schiff base formaedon -NH2-group initiates cyclization. 25-27].