Atr spectrum 100 spectrometer

All the reactions were performed under a dry argon atmosphere. THF was distilled over sodium/benzophenone. Column chromatography separations were achieved on silica gel (40–63 μm). Melting points were measured on a Kofler apparatus. IR spectra were taken on an ATR Spectrum 100 spectrometer (Perkin-Elmer). ¹H- and ¹³C-Nuclear Magnetic Resonance (NMR) spectra were recorded either on an Avance III spectrometer (291 K) at 300 MHz and 75 MHz, respectively, or on an Avance III HD spectrometer (298 K) at 500 MHz and 126 MHz, respectively (Bruker, Billevica, Massachussets, USA). ¹H chemical shifts (δ) are given in ppm relative to the solvent residual peak and ¹³C chemical shifts are relative to the central peak of the solvent signal [46 (link)]. 2,3-Diphenylpyrido[2,3-b]pyrazine (2a) [6 (link)], 8-bromo-2,3-diphenylpyrido[3,4-b]pyrazine (3a) [25 (link),26 (link)] and 7-bromo-2,3-diphenylpyrido[2,3-b] pyrazine (4a) [6 (link)] were prepared as reported previously. The biological activity assays were performed as reported previously [44 (link)].

Column chromatography separations were achieved on silica gel (40–63 μm). Melting points were measured on a Kofler apparatus. InfraRed (IR) spectra were taken on an ATR Spectrum 100 spectrometer (Perkin-Elmer, Waltham, MA, USA) and the main absorption wavenumbers are given in cm⁻¹. ¹H and ¹³C nuclear magnetic resonance (NMR) spectra were recorded on an Avance III spectrometer (291 K) at 300 and 75 MHz, respectively (Bruker, Billevica, MA, USA). ¹H chemical shifts (δ) are given in ppm relative to the solvent residual peak, and ¹³C chemical shifts are relative to the central peak of the solvent signal [80 (link)]. ZnCl₂∙TMEDA was prepared as reported previously [81 (link)].