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-2-arylidenehydrazone-carbodithioates) 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 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.