New thiazol-pyridazine derivatives as antimicrobial and antiviral candidates: Synthesis, and application

In this manuscript, we are motivated to investigate the reaction site-selectivity for the hydrazo thiazole derivatives (6a–c) with different types of active methylene groups such as malononitrile, and ethyl cyanoacetate. Based on their structural investigations and spectrum data, the results of these reactions have been established to be iminopyridazines (7a–c) and 6-oxopyridazine derivatives (8a–c). We tested the ability of the newly synthesized pyridazine derivatives to inhibit the microbes and COVID-19 proteins. Human coronavirus 229E (HCoV-229E) was used to investigate the antiviral efficacy of prepared compounds. Green monkey kidney (Vero-E6) cell lines were used to investigate MTT and cytopathic effect (CPE). The new 6-oxopyridazine derivatives (8a–c) revealed significant inhibitory efficacy and were capable of inhibiting the human coronavirus 229E. Moreover, the antimicrobial result showed that compounds iminopyridazine (7c) followed by iminopyridazine (7a) followed by iminopyridazine (7b) exhibited excellent antimicrobial properties toward all utilized strains, usually greater than that of common reference drugs, with MIC values ranging from 13 to 21 ppm, from 9 to 14 ppm, and from 8 to 19 ppm whereas, the remaining substances appeared to be promising effective. Structure-activity relationship (SAR) revealed that pyridazine scaffolds containing NH group, as well as substituted electron withdrawal group (Cl) in para-position for benzene ring attributed to thiazole moiety have the best activity. The current study successfully illustrated the possible application of heterocyclic derivatives with pyridazie nucleus including thiazole ring as the main compound in the development of dual antiviral (COVID-19) and antibacterial pharmaceuticals in the future.