Study On The Synthesis Of 2-Amino-5-aryloxymethy Lene-1,3,4-thiadiazoles Derivatives

The thiadiazole derivatives are important heterocyclic compounds. They are of great value in medical field for their interesting biological properties, such as anticancer, antifungal, antitubercular, hypnotic, anticonvulsant and anthelmintic activities and cardiovascular effects. They are also important intermediates of dyes and pesticides in organic synthesis. Therefore, the compounds have attracted continued interest. In this thesis, the development of the 2-amino-5-aryloxymethylene-1,3,4-thiadiazoles reaction are reviewed and a series of new methods for the synthesis of 2-N-formyl-5-aryl/arylox-ymethyl-1,3,4-thiadiazoles, 2-chloro-5-aryloxymethylene-1,3,4-thiadiazoles, 2-iodo-5-a-ryloxymethylene-1,3,4-thiadiazoles, 2-hydrazine-5-aryloxymethylene-1,3,4-thiadiazol-les, 1-aryl-2-(5-aryloxymethylene-1,3,4-thiadiazol-2-yl)hydrazine, and hydrazone are described. These methods have the advantages of simple operation, high yield and mild condition. More than many reactions were carried out under environmently friendly conditions. The research results are summarized below:1. An environmental benign procedure for the synthesis of 2-N-formyl-5-aryl/ aryloxymethyl-1,3,4-thiadiazoles has been developed by reaction of 2-amino-5-aryl/aryloxymethyl-1,3,4-thiadiazoles with formic acid in PEG-400. The key advantages of this protocol are the shorter reaction time, higher yields, lower cost, simple workup, and environment-friendly compared to conventional organic solvent reaction. The present method does not involve any hazardous organic solvent or catalyst.2. Under mild condition, the reaction of 2-amino-5-aryloxymethylene-1,3,4-thiadia-zoles with p-TsOH·H2O in acetonitrile solvent afforded 7 new 2-iodo--5-aryloxymethyl-ene-1,3,4-thiadiazoles in excellent. By the optimization of the reaction condition, rapid and high-yield method for preparations of the target compounds were given.3. 1-Aryl-2-(5-aryloxymethylene-1,3,4-thiadiazol-2-yl)hydrazines were synthesized by the reaction of formic acid with 2-hydrazine-5-aryloxymethylene-1,3,4-thiadiazoles, which were synthesized by the reaction of 2-chloro-5-aryloxymethylene-1,3,4-thiadiaz-oles with hydrazine hydrate. we studied affects of varies conditions (such as ratio, solvents and time) on the reactions and obtained the optimum reaction conditions. 4. The reactions of 2-hydrazine-5-aryloxymethylene-1,3,4-thiadiazole with 2 eq. of various aldehdes and ketones under solvent-free and room-temperture grinding condition expeditiously afforded hydrazone in excellent yeilds. This synthetic strategy compared with traditional solution protocols has the advantages of no organic solvent pollution;elevated reaction rate;high yeild and simple work-up procedure.The structures of all compounds were confirmed by elemental analysis;IR;¹H NMR and ¹³C NMR.