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 (J_{C, 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 4. The order is opposite with the endo-anhydride. The carbonyl carbons resonate clearly at lower field in imides than in anhydrides.

Key Words:

• norbornene
• dicarboximide
• NMR spectroscopy