1 H, 13C, 15N, 2D and variable temperature NMR study of the role of hydrogen bonding in the structure and conformation of oxamide derivatives

The structure and conformation of N,N?-bis[(2-hydroxy)phenyl]oxamide (1); N,N?-bis[(2-methoxy)-phenyl]oxamide (2); N,N?-bis(phenyl)oxamide (3); N,N?-bis[(1R,2S)-()-norephedrine]oxamide (4); N,N?-bis[(1R,2R)-()-norpseudoephedrine]oxamide (5); N-[(2-hydroxy)phenyl]methylamide (6); N-[(2-methoxy)phenyl]methylamide (7); N-phenylmethylamide (8); N-[()-norephedrine]-methylamide (9) and N-[()-norpseudoephedrine]methylamide (10) were unambiguously established by 1H, 13C, 15N, 2D and variable temperature NMR spectroscopy. A careful NMR investigation of the conformational behaviour in these systems was relevant. It has been found that the dicarbonylic group in compounds 15 has a trans geometry, stabilized by intramolecular hydrogen bonding and that they possess a C2 axis. Compounds 1 and 2 are planar and compounds 1, 2, 4 and 5 present the amidic proton coordinated by two oxygen atoms.