CONFIGURATIONAL ASSIGNMENTS OF 5-NORBORNENE-2,3-DICARBOXIMIDE AND N-PHENYL-5-NORBORNENE-2,3-DICARBOXIMIDE BY ONE-DIMENSIONAL AND 2-DIMENSIONAL NMR-SPECTROSCOPY

The H-1, C-13, and two-dimensional both homonuclear (H,H-Cosy) and het eronuclear (H,C-Cosy) correlated NMR spectra of endo- and exo-isomers of 5-norbomene-2,3-dicarboximide and N-phenyl-5-norbomene-2,3-dicarbox imide have been examined. Two-dimensional spectra gave evidence for co nfigurations based on long-range couplings. C-13 resonances of carbons 1,4 and carbons 2,3 were ultimately assigned by means of gated decoup led spectra from which the coupling constants ((1)J(C,H)) were determi ned. The literature assignments of the H-1 NMR spectrum of N-phenyl-5- norbornene-endo-2,3-dicarboximide have been revised. The spectra of th e imides were compared with the spectra of endo- and exo-isomers of 5- norbornene-2,3-dicarboxylic anhydride in order to examine the stereo c hemi cal effects of imide ring on the proton and carbon shieldings in 5-norbornene skeleton. When the imide ring is at endo-position of norb ornene skeleton the protons of carbons 2 and 3 resonate at higher fiel d than the protons of carbons 1 and 4. The order is opposite with the endo-anhydride. The carbonyl carbons resonate clearly at lower field i n imides than in anhydrides.