Characterization of Organic Compounds

Unless otherwise stated, all chemical reagents purchased (Merck, Darmstadt, Germany or Aldrich, St. Louis, MO, USA) were of the highest commercially available purity and were used without previous purification. IR spectra were recorded as thin films in a FT-IR Nicolet 6700 spectrometer (Thermo Scientific, San Jose, CA, USA) and frequencies are reported in cm⁻¹. ¹H and ¹³C spectra were recorded on a Bruker Avance 400 Digital NMR spectrometer (Bruker, Rheinstetten, Germany), operating at 400.1 MHz for ¹H and 100.6 MHz for ¹³C. Chemical shifts are reported in δ ppm and coupling constants (J) are given in Hz. HREIMS were measured on Thermo Finnigan MAT95XL mass spectrometers. Silica gel (Merck 200–300 mesh) was used for C.C. and silica gel plates HF 254 for TLC. TLC spots were detected by heating after spraying with 25% H₂SO₄ in H₂O.