Conformational studies by nuclear magnetic resonance. VII—The direct observation of rotational isomers in some enamino carbonyl compounds and their thione derivatives by carbon magnetic resonance
- 1 September 1974
- journal article
- research article
- Published by Wiley in Magnetic Resonance in Chemistry
- Vol. 6 (9) , 499-502
- https://doi.org/10.1002/mrc.1270060911
Abstract
Carbon‐13 magnetic resonance spectra of the s‐cis and s‐trans rotamers of enamino ketones and thiones of the general formula \documentclass{article}\pagestyle{empty}${\rm X =}\mathop {\rm C}\limits^{\rm 1} {\rm (}\mathop {\rm R}\limits^{\rm 1} {\rm)}\mathop {\rm C}\limits^{\rm 2} {\rm H =}\mathop {\rm C}\limits^{\rm 3} {\rm HN}\mathop {{\rm R}_{\rm 2}}\limits^{\rm 4}$ (where × = O or S and R‐1, R‐4 = alkyl) have been obtained. With dimethylaminoacrolein and its thione analogue, restricted rotation could only be observed in the latter. The chemical shift differences between rotamers and homologues are attributed to changes in conjugation and to induced bond polarisation, both these factors resulting from steric strain. In particular, nonplanar deformations of the s‐trans rotamers are deduced from their C‐2 chemical shift values.Keywords
This publication has 14 references indexed in Scilit:
- Conformational studies by nuclear magnetic resonance—V:13C spectra and structural problems of enamino carbonyl compoundsMagnetic Resonance in Chemistry, 1973
- Determination of conformational barriers in 1,5-cyclooctadiene by proton and carbon-13 nuclear magnetic resonanceJournal of the American Chemical Society, 1973
- Ring inversion study of γ-1,2,3,4,5,6-hexachlorocyclohexane using 13C nuclear magnetic resonanceJournal of Magnetic Resonance (1969), 1973
- Determination of conformational energy barriers in medium- and large-ring cycloalkanes by proton and carbon-13 nuclear magnetic resonanceJournal of the American Chemical Society, 1972
- 13CMR‐Tieftemperatur‐Untersuchungen an Cyclooctan‐KonformerenMagnetic Resonance in Chemistry, 1972
- Conformational studies by nuclear magnetic resonance—IV: Restricted rotation in vinylogous thioamidesMagnetic Resonance in Chemistry, 1972
- Conformational studies by nuclear magnetic resonance—III: ASIS and protonation studies of the rotational isomerism of enamino aldehydes and ketonesMagnetic Resonance in Chemistry, 1972
- Conformational studies by nuclear magentic resonance—II: The effect of steric factors on hindered rotation in enamino aldehydes and ketonesMagnetic Resonance in Chemistry, 1972
- Direct detection of the axial conformer of methylcyclohexane by 63.1MHz carbon-13 nuclear magnetic resonance at low temperaturesJournal of the American Chemical Society, 1971
- Carbon-13 nuclear magnetic resonance spectroscopyQuarterly Reviews, Chemical Society, 1965