68839-69-0Relevant articles and documents
Reactions of 2-Arylthio-and 2-Arylsulfonyl-1-nitro-1-phenylethenes with Amines
Kuz'mina,Lipina,Kropotova,Berkova,Pavlova
, p. 82 - 86 (2003)
2-Arylthio- and 2-arylsulfonyl-1-nitro-1-phenylethenes react with amines to give the corresponding nitroenamines whose configuration (E or Z) depends on the amine structure. Primary amines gives rise to Z-nitroenamines, secondary cyclic amines with 2-aryl
Etude structurale d'α-amino β-nitrostilbenes
Allade, Irenee,Dubois, Pierre,Levillain, Pierre,Viel, Claude
, p. 339 - 344 (2007/10/02)
Several nitroenamines were prepared by reacting various amines with Z-α,β-dinitrostilbene and their structure was determined by IR, 1H-NMR and UV spectrometry.Indeed, various structures have been suggested for these compounds (enamine, imine, imonium ion) as well as the possibility of an E or Z configuration. 1) Primary and secondary stilbene-nitroenamines.In case of these nitroenamines, we were able to: --confirm the creation of an intramolecular H-bond by the absence of the N-H band around 3300 cm-1 in the IR and, above all, by the considerable deshielding of the NH signal found at δ 11-12 in the case of aliphatic and aromatic nitroenamines (whereas the same signal is found, for example, at δ 4 for orthonitroaniline); --eliminate the imine form.Indeed, there is no evidence for the existence of a singlet between δ 4-6 in the proton NMR spectrum; --eliminate the nitronic acid form, because of the existence in the 1H-NMR, of a coupling between the proton carried by the α-carbon (vis-a-vis the nitrogen) and the proton carried by the nitrogen itself.This is confirmed by the presence of the N-H2 band in the IR (2400 cm-1). This intramolecular H-bond has 3 consequences: a) The double bond does not appear to be conjugated with the aromatic ring.This is confirmed by the analysis of the UV spectra of the stilbene nitoenamines which show an absorption maximum identical or close to that of the simpler ethylenic homologues; b) The existence of an equilibrium between the enamine form and the imonium ion: solubility studies show that the nitroenamines possess a certain polarity; c) The predominance of the Z-configuration.This is, moreover, confirmed by the relative shielding of the aromatic stilbene protons (a singlet at δ 7.1).Indeed, it has been shown that the aromatic protons of Z-stilbene, Z-α,β dinitrostilbene or Z-α cyano β-nitrostilbene absorb at a lower field than their E isomers. 2) Tertiary stilbene nitroenamines.The structure of these nitroenamines is more difficult to study.However, the similarity of the data (IR, 1H-NMR) suggests also a Z-configuration.Indeed, in the NMR, the aromatic protons have the same chemical shift (around δ 7.2) as those of the secondary nitroenamines.In addition, there is a great similarity between the 2 groups of nitroenamines as far as the asymetrical and symetrical absorption bands of the NO2 group are concerned.If the enamine-imonium ion equilibrium is valid, for the same reason as above, the conjugation of the double bond with the aromatic ring appears to be more important in this case as indicated by a comparison of the UV spectra of the tertiary stilbene nitroenamines with those of their simpler ethylenic homologues.
