Synthesis and Characterization of Novel Polythiadiazoles from Bis-hydrazonoyl Dichlorides and Bis-(methyl-2-arylidene hydrazone carbodithioates)

Background: Thiadiazoles exhibit a variety of biological activities, including antimicrobial, antiviral, antituberculosis, carbonic anhydrase inhibitor, antitrypanosomal agent, and anticonvulsant properties. Methods: The new polymers are made in two distinct stages. The first stage is to prepare the starting material bis-(methyl hydrazoncarbodithioate) via a condensation reaction between methyl-hydrazinecarbodithioate and dicarbonyl compounds in suitable solvent as isopropyl alcohol. The second stage for the synthesis of the final products poly(1,3,4-thiadiazoles) derivatives is the suitable bis-hydrazonoyl chloride reacted with an equal molar ratio of bis-(methyl-2-arylidenehy-drazonecarbodithioates) in dimethyl sulfoxide, with triethylamine and reflux until the methanethiol gas stopped evolving. FT-IR (Fourier transform infrared spectroscopy), NMR (Nuclear magnetic resonance), and thermal investigation were used to identify and characterize the final products. Results: This work effectively synthesized new derivatives of poly(1,3,4-thiadiazoles) in good yields via the reaction of bis-hydrazonoyl dichlorides with bis-(methyl-2-arylidenehydrazonecarbodithioates). Two routes can be used to explain how the final poly(1,3,4-thiadiazoles) compounds are formed. The first route can be explained by nucleophile substitution of thiolate of bis(methyl-2-arylidenehydrazonecarbodithioates) to the chlorinated carbon of bis-hydrazonoyl dichlorides, followed by removal of HCl (hydrochloric acid) to provide an intermediate (S-alkylated). This intermediate at once leads to an intramolecular cyclo-polycondensation by the exclusion of methanethiol gas to produce our ending products poly(1,3,4-thiadiazoles). The second route concluded [3+2] cycloaddition of 1,3-dipolar cycloadditions of nitrilimines (generated in situ by treatment of bis-hydrazonoyl dichlorides with triethylamine) to thione (C=S) followed by removal of methanethiol to give poly(1,3,4-thiadiazoles) as depicted in schematic diagram. Conclusion: In this article, we reported an efficient method for the synthesis of the novel poly(1,3,4-thiadiazoles) from the reaction of bis-(methyl-2-arylidenehydrazonecarbodithioates) with bis-hydrazonoyl halides.