17O NMR Study of Steric Interactions in Hindered N-Substituted Imides

Article abstract of DOI:10.1021/jo00392a026

17O NMR spectroscopic data (natural abundance in acetonitrile at 75 deg C) were obtained for a series of N-substituted phthalimides (1-11),a series of N-substituted succinimides and maleimides (12-19),and N-substituted phthalamides (20-22).The 17O NMR data showed large deshielding effects as the steric bulk of the N-substituent increased ; introduction of a 3-substituent in the phthalimide series produced additional deshielding.The deshielding effects of 3-substitution and N-substitution in the phthalimides were found to be roughly additive.The results correlated with in-plane bond angle distortions (X-ray results and molecular mechanics calculations.)The results for N-arylphthalimides showed that the aromatic ring was rotated out of the plane (torsion angle effect) in those cases.