Synthesis and Characterization of Pyrazole Derivatives

Melting points were measured in open capillary tubes on a BÜCHI B-545 melting point apparatus (BÜCHI Labortechnik AG, Flawil, Switzerland) and were uncorrected. Elemental analyses (C, H, N) were performed using the Perkin-Elmer 2400 CHN analyzer (PerkinElmer, Waltham, MA, USA), with results within ±0.4% of the theoretical values. The 500 MHz ¹H and 100 MHz ¹³C NMR spectra were recorded on a Varian Unity Plus 500 (500 MHz) spectrometer (Varian Inc., Paulo Alto, CA, USA). All spectra were recorded at room temperature, unless specified otherwise, and were referenced internally to solvent reference frequencies. Chemical shifts (δ) are presented in ppm and coupling constants (J) in Hz. LC-MS spectra were obtained on a Finnigan MAT INCOS-50 (Thermo Finnigan LLC, San Jose, CA, USA). The reaction mixture was monitored by thin-layer chromatography (TLC) using commercial glass-backed TLC plates (Merck Kieselgel 60 F254, Merck, Darmstadt, Germany). Solvents and reagents that are commercially available were used without further purification. The synthesis of 1,3-diphenyl-1H-pyrazole-4-carbaldehyde (i) and thiazolidine-2,4-dione (ii) was carried out according to methods described in references [53 (link),54 ], respectively.