SYNTHESIS, CHARACTERIZATION, ENZYMATIC ACTIVITY OF SOME PYRAZOLINE DERIVATIVES, AZO DYES, AND CHALCONES DERIVED FROM ETHYL 4-(TRIFLUOROMETHYL)BENZOATE

Abstract: This study reports the use of 4-(trifluoromethyl)benzoate as a key synthone for preparing a series of heterocyclic derivatives. Reaction completion was verified by thin-layer chromatography (TLC), and the products were characterized by physical properties (color, yield, and melting point), Fourier-transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance spectroscopy (¹H- and ¹³C-NMR). The corresponding hydrazide was obtained by reacting 4-(trifluoromethyl)benzoate with aqueous hydrazine, confirmed by the NH₂ stretching bands at 3359 and 3326 cm⁻¹ (FT-IR) and a signal at 4.56 ppm (¹H-NMR). Subsequent condensation with ethyl acetoacetate produced a pyrazoline intermediate, exhibiting an absorption band at 1606 cm⁻¹ (FT-IR) and a carbon signal at 161.13 ppm (¹³C-NMR). This intermediate was then employed in the synthesis of azo dyes by coupling pyrazolines with substituted anilines in pyridine, confirmed by characteristic FT-IR bands at 1446–1440 cm⁻¹ and ¹H-NMR signals at 2.23–2.39 ppm (CH). Further reactions with benzaldehyde derivatives in dioxane yielded chalcones, where ¹H-NMR signals at 8.14–8.43 ppm corresponded to olefinic protons of the chalcone moiety. Finally, the enzymatic activity of selected compounds (SH1, SH2, SH3, SH6) was evaluated against alkaline phosphatase (ALP) using a phosphinate substrate, revealing significant bioactivity.