Fluka silica gel 60

All commercial chemicals used were of analytical grade and supplied by Sigma-Aldrich, Frontier Scientific, Inc., Tokyo Chemical Company and Acros chemicals and used without further purification unless otherwise stated. Flash column chromatography was carried out using Fluka Silica Gel 60 (230–400 mesh; Merck. Melting points are uncorrected and were measured with a Stuart SP-10 melting point apparatus. A Bruker Advance III 400 MHz spectrometer was employed for ¹H (400.13 MHz), and ¹³C (100.61 MHz) NMR spectra. All NMR experiments were performed at room temperature. Mass spectrometry analysis was performed with a Q-Tof Premier Waters MALDI quadrupole time-of-flight (Q-TOF) mass spectrometer equipped with Z-spray electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) sources either in a positive or negative mode with DCTB (trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-propenylidene]malononitrile) as the matrix. UV-visible absorption measurements were performed using a Shimadzu MultiSpec-1501.

All solvents and reagents were purchased from Merck (Merck Bulgaria EAD, Sofia, Bulgaria). The melting point was determined on a Boetius hot stage apparatus and is uncorrected. Elemental analyses were performed with a TruspecMicro (LECO, Mönchengladbach, Germany). PID was characterized using IR, ¹H-NMR, and ¹³C-NMR. IR spectra were determined on a VERTEX 70 FT-IR spectrometer (Bruker Optics, Ettlingen, Germany). ¹H-NMR and ¹³C-NMR spectra were recorded on a Bruker Avance III HD 500 spectrometer (Bruker, Billerica, MA, USA) at 500 MHz (¹H-NMR) and 125 MHz (¹³C-NMR), respectively. Chemical shifts are given in relative ppm and were referenced to tetramethylsilane (TMS) (δ = 0.00 ppm) as an internal standard; the coupling constants are indicated in Hz. The NMR spectra were recorded at room temperature (ac. 295 K). The purity was determined by TLC using several solvent systems of different polarities. TLC was carried out on precoated 0.2 mm Fluka silica gel 60 plates (Merck Bulgaria EAD), using chloroform:n-hexane:methanol: acetone = 4:4:1:1 as a chromatographic system.

The following instruments and parameters were used: melting points Boetius PHMK apparatus; IR spectra: KBr pellets, 400–4000 cm^–1 Thermo Mattson Satellite FTIR spectrophotometer; ¹H and ¹³C NMR: Varian Unity 500 plus apparatus at 500 MHz; chemical shifts are expressed in parts per million (ppm) relative to TMS as internal standard. Elemental analyses for C, H, and N were performed on a 2400 Series II CHN Elemental Analyzer (Perkin Elmer, Shelton, CT, USA) and are in agreement with the theoretical values within ±0.4% range. Thin-layer chromatography (TLC) was performed on Merck Kieselgel 60 F₂₅₄ plates and visualized with UV. Gravity column chromatography was performed on Fluka silica gel 60 of particle size 35–75 μm and 220–440 mesh (Sigma–Aldrich Chemie, Steinheim, Germany). The starting compounds (4–chloro–2–mercapto–5-methylbenzenesulfonamide (1)) [33 ] and cinnamic acid derivatives (10–15) were synthesized according to the literature sources [34 (link),35 (link),36 (link)].