Reagent-grade chemicals
were purchased
from Sigma-Aldrich or Fluorochem and were used without further purification.
All reactions were monitored by thin-layer chromatography (TLC) performed
on silica gel Merck 60 F254 plates; the spots were visualized by UV
light (λ = 254 and 366 nm) and an iodine chamber. Melting points
were determined on a Büchi B-450 apparatus in capillary glass
tubes and are uncorrected. Flash chromatography purification was performed
on a Merck silica gel 60, 0.040–0.063 mm (230–400 mesh)
stationary phase using glass columns with a diameter between 1 and
4 cm. Nuclear magnetic resonance spectra (1H NMR and 13C NMR recorded at 500 and 125 MHz, respectively) were obtained
on Varian INOVA spectrometers using CDCl3, acetone-d6, CD3OD, and DMSO-d6 with a 0.03% of TMS as an internal standard. Coupling
constants (J) are reported in hertz. Signal multiplicities
are characterized as s (singlet), d (doublet), t (triplet), q (quartet),
m (multiplet), br (broad), and app (apparent). Purities of all compounds
were ≥95% as determined by microanalysis (C, H, and N) that
was performed on a Carlo Erba instrument model E1110; all the results
agreed within ±0.4% of the theoretical values.
were purchased
from Sigma-Aldrich or Fluorochem and were used without further purification.
All reactions were monitored by thin-layer chromatography (TLC) performed
on silica gel Merck 60 F254 plates; the spots were visualized by UV
light (λ = 254 and 366 nm) and an iodine chamber. Melting points
were determined on a Büchi B-450 apparatus in capillary glass
tubes and are uncorrected. Flash chromatography purification was performed
on a Merck silica gel 60, 0.040–0.063 mm (230–400 mesh)
stationary phase using glass columns with a diameter between 1 and
4 cm. Nuclear magnetic resonance spectra (1H NMR and 13C NMR recorded at 500 and 125 MHz, respectively) were obtained
on Varian INOVA spectrometers using CDCl3, acetone-d6, CD3OD, and DMSO-d6 with a 0.03% of TMS as an internal standard. Coupling
constants (J) are reported in hertz. Signal multiplicities
are characterized as s (singlet), d (doublet), t (triplet), q (quartet),
m (multiplet), br (broad), and app (apparent). Purities of all compounds
were ≥95% as determined by microanalysis (C, H, and N) that
was performed on a Carlo Erba instrument model E1110; all the results
agreed within ±0.4% of the theoretical values.