Vnmrs 400 mr

Chemical reagents and solvents were purchased from Sigma-Aldrich (St. Louis, MO, USA) with analytical grade purity. Melting points were determined in open capillaries on a Buchi apparatus and are uncorrected. Thin-layer chromatography (TLC) was carried out on aluminium-supported silica gel plates (Merck 60 _F254) with visualization by UV light 254 nm in the appropriated system for each compound. The Infrared spectra (1% KBr, cm⁻¹ pellets) were recorded on a Bruker IFS66 spectrophotometer (Billerica, MA, USA), the wave numbers were given in cm⁻¹ and are uncorrected. The ¹H NMR and ¹³C NMR spectra were recorded on a VARIAN VNMRS 400-MR (Palo Alto, CA, USA), 400 MHz for ¹H and 75.4 MHz for ¹³C. The ¹H spectra were recorded in DMSO-d₆ while ¹³C spectra were recorded in CDCl₃ and DMSO using tetramethylsilane (TMS) as the internal standard. The peak and abbreviations were used to indicate multiplicity: s (singlet), d (doublet), dd (double doublet), ddd (double doublet, doublet), t (triplet), and m (multiplet). The chemical shifts were reported in δ units and the coupling constants (J) were reported in Hertz. Mass spectra were recorded on a Varian MAT 711 spectrometer (Palo Alto, CA, USA) 70 eV electron impact.

The chemical reagents were supplied by Sigma-Aldrich (USA) and were used without further purification. Purity of the compounds was checked using thin layer chromatography (TLC) plates (silica gel G) in the appropriated system for each compound. The spots were located with short (254 nm)/long (365 nm) UV wavelength.
All melting points were measured in a capillary tube on a Quimis apparatus. Infrared spectra of 1% KBr pellets were recorded using a Bruker IFS66 spectrometer. ¹H NMR and ¹³C NMR spectra were measured on a VARIAN VNMRS 400-MR, using 400 MHz for ¹H and 75.4 MHz for ¹³C in CDCl₃ and acetone-d₆ maintained at 25°C using Me₄Si (TMS) as an internal standard. The chemical shifts were reported in δ units and the coupling constants (J) were reported in hertz. The following abbreviations were used to indicate the peak multiplicity: s (singlet), d (doublet), dd (double doublet), t (triplet), and m (multiplet). C, H, N, and S analyses were performed with a Carlo Erba elemental analyzer, model EA1108. Mass spectra were recorded on a Varian MAT 711 spectrometer at an electron impact of 70 eV. The synthesized compounds are shown in Scheme 1, showing the respective substituent.