ISSN:
0749-1581
Keywords:
Configurations
;
Conformations
;
Imidates
;
NOE
;
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
A new method for determining conformations and configurations of imidate esters was developed based on NOE difference spectra in CDCI3. As a test of the method, methyl N-methylacetimidate was determined to exist in the E configuration, ap conformation, in agreement with assignments by homoallylic coupling and dipole moment data. Methyl N-tert-butylformimidate, for which existing methods were not suitable, was also determined to exist as E-ap. Two methyl benzimidates were investigated, the N-methyl derivative 2, which was E-ap, and the N-tert-butyl derivative 6, which exhibited an unusually easy E/Z isomerization at room temperature (Tc = 24°C). At -58 °C, resolved spectra showed the E/Z isomers of 6 in a 40:60 ratio. From NOE data (E)-6 was determined to exist mostly as the ap conformer and (Z)-6 as the sp conformer. These results, in agreement with chemical shift data, can be interpreted in terms of the unusual steric requirements of the tert-butyl group.
Additional Material:
1 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/mrc.1260250604
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