H-1, C-13, N-15, 2D AND VARIABLE-TEMPERATURE NMR-STUDY OF THE ROLE OFHYDROGEN-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]methylami de (10) were unambiguously established by H-1, C-13, N-15, 2D and vari able temperature NMR spectroscopy. A careful NMR investigation of the conformational behaviour in these systems was relevant. It has been fo und that the dicarbonylic group in compounds 1-5 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 pres ent the amidic proton coordinated by two oxygen atoms.