1H nuclear magnetic resonance (1H NMR) spectra were obtained on an Avance 300 MHz NMR spectrometer (Bruker, Germany) with tetramethylsilane as internal standard and CDCl3 as solvent
1H nuclear magnetic resonance (1H NMR) spectra were obtained onan Avance 300 MHz NMR spectrometer (Bruker, Germany) withtetramethylsilane as internal standard and CDCl3 as solvent