Configurational Assignments of 5-Norbornene-2,3-dicarboximide and N-Phenyl-5-norbornene-2,3-dicarboximide by One- and Two- Dimensional NMR Spectroscopy

Abstract The H, 13C, and two-dimensional both homonuclear (H, H-Cosy) and heteronuclear (H, C-Cosy) correlated NMR spectra of endo- and exo-isomers of 5-norbornene-2,3- dicarboximide and N-phenyl-5-norbornene-2,3- dicarboximide have been examined. Two-dimensional spectra gave evidence for configurations based on long-range couplings. 13C resonances of carbons 1,4 and carbons 2,3 were ultimately assigned by means of gated decoupled spectra from which the coupling constants (JC, H) were determined. The literature assignments of the H NMR spectrum of N-phenyl-5-norbornene- endo-2,3-dicarboximide have been revised. The spectra of the imides were compared with the spectra of endo- and exo-isomers of 5-norbornene-2,3-dicarboxylic anhydride in order to examine the stereochemical effects of imide ring on the proton and carbon shieldings in 5-norbornene skeleton. When the imide ring is at endo-position of norbornene skeleton the protons of carbons 2 and 3 resonate at higher field than the protons of carbons 1 and ...