## 2 Results and Discussion
### Synthesis
The constructed thiazol-4-one scaffold **9** underwent condensation with three para-substituted benzaldehyde derivatives in glacial CH\({}_{3}\)COOH and anhydrous CH\({}_{3}\)COONa (Knoevenagel condensation reaction) furnishing the corresponding 2-(4-antipyrinylthiazol-2-ylamino)-5-(substituted-benzylidene)-thiazol-4(5\(H\))-one derivatives **10a-c** in good yields, see Scheme 3. The chemical structures of **10a-c** were determined based on their compatible spectral analyses. Thus, the IR spectrum of **10a** showed the characteristic absorptions at 3176 and 1698 cm\({}^{-1}\) referring to the functional groups -NH- and carbonyl (C=O), respectively. The \({}^{1}\)H NMR spectrum of the same scaffold exhibited a singlet for three protons at \(\$\) 2.61 ppm (CH\({}_{3}\)-C), a singlet for three protons at \(\$\) 2.28 ppm (CH\({}_{3}\)-N), a singlet for three protons at \(\$\) 3.84 ppm (OCH\({}_{3}\)), and a doublet for two protons at \(\$\) 7.14 ppm (aromatic protons). The aromatic and thiazole C-5 protons resonated as a multiplet (\(\$\) 7.28-7.62 ppm), the olefinic proton resonated as a singlet at \(\$\) 7.73 ppm, while the proton on N-H function resonated as a singlet at \(\$\) 12.62 ppm. In compounds **10a-c**, the \(Z\) conformation of the exocyclic C=C double bond was assigned on the basis of \({}^{1}\)H NMR spectroscopy and on the basis of literature data for analogous 4-thiazoltones [33]. The \({}^{1}\)H NMR spectra of compounds **10a-c** showed only one kind of methine proton that, deshielded by the adjacent C=O, was detected at 7.73-7.78 ppm, which are higher chemical shift values than those expected for E isomers. Condensation reaction of equimolar amounts of chloroacetamido derivative **1** and malononitrile in absolute ethyl alcohol containing a few drops of triethylamine afforded the corresponding condensation product 2-amino-1-(4-antipyrinylthiazol-2-yl)-3-cyano-4,5-dihydro-5-oxo-1\(H\)-pyrrole (**12**) which was identified based on its compatible spectral analyses, see Scheme 4. Thus, the infrared spectrum of compound **12** exhibited the characteristic absorptions at 3293, 3191, 2216, and 1705 cm\({}^{-1}\) related to the functional groups amino (NH\({}_{2}\)), nitrile (C\(\equiv\)N), and carbonyl (C=O), respectively. In the \({}^{1}\)H NMR spectrum, the protons of two methyl, methylene, thiazole-H5, and amino functions were secured by the presence of their characteristic signals at \(\delta\) 2.65 ppm (singlet), \(\delta\) 3.32 ppm (singlet), \(\delta\) 4.36 ppm (singlet), \(\delta\) 7.29 ppm (singlet), and \(\delta\) 12.47 ppm (singlet), respectively. Treatment of chloroacetamide derivative **1** with salicaldehyde in DMSO containing potassium carbonate was achieved by stirring the reaction mixture for 8 h followed by neutralization with dilute HCI to furnish \(N\)-(4-antipyrinylthiazol-2-yl) benzofuran-2-carboxamide (**13**). It was reasoned that the chlorine atom in acetamido derivative **1** could be substituted by nucleophiles, so the plausible pathway for the formation of benzofuran derivative **14** could be via formation of intermediate **13**, which subsequently underwent a condensation reaction between the formyl and active methylene group, see Scheme 5. The structural proof of compound **14** was determined based on its correct spectral analyses. Thus, the infrared spectrum of compound **14** showed absorptions at 3369 and 1689 cm\({}^{-1}\) to secure the functional groups (N-H) and (C=O), respectively. The \({}^{1}\)H NMR spectrum clearly indicated the presence of a singlet for three protons at 2.62 (CH\({}_{3}\)-C), a singlet for three protons at 3.33 (CH\({}_{3}\)-N), a singlet for one proton at 7.28 ppm (thiazole-H5), a multiplet for ten protons in the region of 6 7.36-7.71 ppm (aromatic-H and furan-H3), and a singlet for one proton at 8 12.31 ppm (NH).