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  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 25 (1987), S. 480-483 
    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
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