## 3 Results and Discussion
### Chemistry
The integral intensities of these signals correspond to the molecular structure of hydrazone **13**. In the \({}^{13}\)C NMR spectrum of compound **13**, the carbon spectral lines were in good agreement with the target structure (Supplementary Materials). In the next step, to improve the biological properties of hydrazones, some of them, viz. **9-12**, were alkylated with ethyl iodide in DMF in the presence of potassium hydroxide and potassium carbonate in the reaction mixture. The reactions were carried out at room temperature for 24 h. Products **19-22** were isolated by adding water to the reaction mixtures. Comparison of the NMR spectra of parent compounds **9-12** and products **19-22** indicated an obvious difference between them and proved that \(N\)-ethylation had taken place. The \({}^{1}\)H NMR spectra of these derivatives showed triplets at around 1.11 ppm with \(J\) of 6.9 Hz for the protons of the CH\({}_{3}\)CH\({}_{2}\) group, and two protons of the CH\({}_{2}\) of the same group were expressed as multiplets approx. in the range of 3.96 to 4.16 ppm (Supplementary Files, Figures S35, S37, S39 and S41). As an effort toward the synthesis of small molecules as biologically active compounds, the 3,5-dimethylpyrazole-**23** and 2,5-dimethylpyrrole-based **24** structures were prepared. Such molecules were easily obtained by using the condensation of acid hydrazide with diketones approach as depicted in Scheme 2. The targeted compounds were characterized using spectral methods, which data corroborated the assumed structures. To generate 3,5-dimethylpyrazole **23**, condensation was carried out using 1.6 equiv. of pentane-2,4-dione in propan-2-ol at reflux for 3 h. To generate compound **24**, having a 2,5-dimethylpyrrole cycle, hydrazide **4** was reacted with two equiv. of hexane-2,5-dione and the reaction was catalyzed by glacial acetic acid. Next, the intramolecular cyclization of acid hydrazide **4** with carbon disulfide was carried out and resulted in 1,3,4-oxadiazol-2(3\(H\))-thione **25** in 70% yield. The analysis of the NMR spectra of the initial compound **4** and its cyclized derivative **25** showed strong differences indicating the formation of product **25**. In the \({}^{1}\)H NMR spectrum of **4**, the NH proton was observed at 9.28 ppm, whereas in the same spectrum of **25**, the NH singlet was shifted to 14.35 ppm and demonstrated the thiol-thione tautomerism. The examination of the \({}^{13}\)C NMR spectrum of oxadiazole thione **25** revealed the correspondence of the peaks of carbon atoms with the structure of the compound, and the resonance line at 178.07 ppmconfirmed the presence of the C=S group in the formed structure (Supplementary Files, Figures S47 and S48). 4-Amino-1,2,4-triazole **26** was prepared in a two-step procedure from hydrazide **4** by reaction with carbon disulfide and subsequent interaction of the resulting \(N\)-potassium thiocarbamate salt with hydrazine monohydrate. Compound **26** was isolated in 65% yield. The spectral data of 5.58 and 13.63 (\({}^{1}\)H NMR, NH\({}_{2}\)NH) ppm, as well as 152.68 and 167.28 (\({}^{13}\)C NMR, N-C=N, C=S) ppm, were in accord with the structure of the 4-amino-1.2.4-triazole cycle (Supplementary Files, Figures S49 and S50). It should be noted that the structures of all target compounds **2**-**26** were characterized by IR, \({}^{1}\)H and \({}^{13}\)C NMR spectroscopic methods, and microanalysis data, and they fully corroborated the assumed structures.