silica gel 60 (70–230 mesh ASTM). Analytical thin-layer chromatography
(TLC) was performed on silica gel 60 F254 aluminum sheets. 1H- and 13C NMR spectra were recorded on a Bruker
AVANCE 300 NMR spectrometer or a Bruker AVANCE NEO 500 NMR spectrometer.
Fourier-transform infrared spectra were obtained using universal attenuated
total reflectance attached on a PerkinElmer Spectrum One spectrometer.
HRMS data were recorded on a Bruker Daltonics (microTOF) instrument.
Melting points were determined using a Griffin melting point apparatus
and were uncorrected.