Kieselgel 60 f254 precoated plates

The melting
points of the compounds were determined in open capillary tubes using
a Buchi B540 melting point apparatus without correction. The progress
of the reactions was monitored using silica gel thin-layer chromatography
(TLC) Kieselgel 60 F₂₅₄ precoated plates (Merck, Germany)
and visualized under a UV lamp at a wavelength of 254 nm. NMR spectra
recorded in DMSO-d₆ were obtained on a
Varian Mercury FT-NMR spectrometer (Varian, Inc., Palo Alto, California)
using tetramethylsilane as an internal standard. Spectra were acquired
at 400 or 500 MHz for ¹H NMR, and at 125 or 100 MHz for ¹³C NMR. The values for chemical shifts (δ values) and
coupling constants (J values) are provided in ppm
and Hz, respectively. Mass analyses were performed on a Waters ZQ
Micromass liquid chromatography–mass spectrometry (LC–MS)
spectrometer (Waters Co., Milford, MA) using electrospray ionization.
Elemental analyses were performed using Leco CHNS 932 Elemental Analyzer
(Leco-932, St. Joseph, MI).

All materials were obtained from commercial suppliers and used without further purification. Reactions were monitored by TLC (Kieselgel 60 F₂₅₄ precoated plates, E. Merck, Germany), the spots were detected by exposure to UV lamp at 254 nm. Melting points were determined on an electrothermal melting point apparatus (Stuart Scientific Co.) and were uncorrected. NMR spectra were measured in DMSO-d₆ on a Bruker AV-400 spectrometer (Bruker Bio Spin Corp., Billerica, MA, USA) (400 MHz for ¹H, 101 MHz for ¹³C, and 40.15 MHz for ¹⁵N) at Florida Institute of Technology, USA. The ¹H and ¹³C chemical shifts are given relative to internal standard TMS = 0, and external liquid ammonia = 0 for ¹⁵N. Coupling constants are stated in Hz. Correlations were established using ¹H-¹H COSY, and ¹H-¹³C and ¹H-¹⁵N HSQC and HMBC experiments. Vario EL III German CHN Elemental analyser model was used for Elemental analysis.

All commercial chemicals (Aldrich, Alpha, Fischer, SDS) were used as purchased and solvents (Fischer, SDS, Scharlau) purified by the standard procedures prior to use⁴³ . Reactions were monitored by Thin Layer Chromatography (TLC) (Kieselgel 60 F254 precoated plates, E. Merck, Germany), the spots were detected by exposure to UV light at λ 254 nm, and colorization with 10% ninhydrin spray, and further heating of the plate. Melting points (mp) were determined with Mel-Temp apparatus in open capillaries and were uncorrected. Separations by flash column chromatography were performed on Merck 60 silica gel (0.063–0.2 mesh). NMR spectra were recorded on a Bruker Avance 400 MHz, Varian Mercury 400 MHz (400 MHz for ¹H, 100 MHz for ¹³C) or Varian Mercury 200 MHz (200 MHz for ¹H, 500 MHz for ¹³C). The spectra were measured either in CDCl₃, methanol-d₆ or DMSO-d₆, using tetramethylsilane (TMS) as internal standard, chemical shifts (δ) are given in ppm and coupling constants (J) in Hertz. High resolution mass spectra (HRMS) were obtained by electron spray ionization-mass spectrometry (ESI–MS) technique (5 kV) on a QSTAR XL mass spectrometer.