Quinoxalines XIV.†Synthesis, 1H, 13C, 15N NMR spectroscopic, and quantum chemical study of 1H-pyrazolo[3,4-b]quinoxalines (flavazoles)

1H, 13C, 15N NMR chemical shifts of 42 flavazoles were detected experimentally and some of them were calculated using quantum chemical methods [ab initio at different levels of theory (HF/6-31G* and B3LYP/6-31G*)]. Barriers to rotation about the amidic C-N bond were also estimated.