Resonance magnetique dynamique du carbone I. Application a l'etude conformationnelle d'amidines substituees

Filleux, M.L.; Naulet, N.; Dorie, J.; Martin, G. J.; Pornet, J.; Miginiac, L.

doi:10.1016/s0040-4039(01)82512-0

Cited by 29 publications

(4 citation statements)

References 13 publications

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“…Coalescence of the three CH 2 signals of the N -ethyl groups (and also of the CH 3 and aromatic proton signals, although these were not used for analysis because of considerable signal overlap) occurs at higher temperatures. The Gibbs activation barrier Δ G ⧧ of 68 ± 1 kJ mol -1 derived from line shape analyses was comparable to that for other amidines with substituents that were more sterically demanding than methyl groups …”

Section: Discussionsupporting

confidence: 61%

“…The restricted rotation around the C−N partial double bond in N -substituted amidines and amidinium salts has been known for a long time. 13d,, The majority of previous studies have been carried out with highly substituted amidines since complications by tautomerization and proton exchange could thus be avoided. Rotational barriers were highly dependent on steric effects and the type of substituent on the amidine group.…”

Section: Discussionmentioning

confidence: 99%

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Noncovalent Interactions between Tetrazole and anN,N‘-Diethyl-Substituted Benzamidine

et al. 2001

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Amidines have long been known to form strong noncovalent complexes with carboxylates and phosphates. However, their interaction with tetrazoles, which are acidic heterocycles and important bioisosteric replacements for carboxylic acids in medicinal chemistry, has remained unexplored so far. The binding of a tetrazole to an N,N'-diethyl-substituted benzamidine has been studied for the first time by X-ray crystallography, solution NMR methods, and electrospray mass spectrometry. The amidinium group of model complex 3 was found to prefer an E,Z configuration in the crystal. Benzamidinium and tetrazolate groups alternate along an infinite chain of hydrogen bonds and salt bridges between the amidine-NH groups and the two tetrazole-N atoms next to the ring carbon. In solution, a 1:1 complex was evident from Job's method of continuous variation, and an association constant of 4.0 x 10(3) +/- 1.6 x 10(3) M(-)(1) (in CDCl(3)/CD(3)CN, 6:1) could be determined by (1)H NMR dilution experiments. Tetrazolate was not only found to be a weaker ligand than carboxylates but, surprisingly, the binding mode also changed with concentration in neat CDCl(3). At low concentrations, the amidine group in complex 3 adapted an E,E configuration as it does in a related carboxylic acid complex 4. With increasing concentration, the E,Z isomer starts to predominate. A free activation enthalpy DeltaG(298)() of 64 +/- 1 kJ mol(-)(1) for the E,E to E,Z isomerization was determined by line shape analysis at different magnetic fields. Binding strength was further probed in a competition experiment between a bisamidine, a carboxylate, and a tetrazolate by electrospray mass spectrometry.

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Section: Discussionsupporting

confidence: 61%

Section: Discussionmentioning

confidence: 99%

Noncovalent Interactions between Tetrazole and anN,N‘-Diethyl-Substituted Benzamidine

et al. 2001

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“…Gibbs Δ E was also assessed and a potential energy barrier for the dimethyl moiety rotation of 21.98 kcal/mol. was obtained, without zero-point energy (ZPE) correction, which is consistent with experimental values obtained for substituted benzamidine . The imaginary frequency at the global maximum is 126.9 i cm –1 .…”

Section: Resultssupporting

confidence: 87%

“…was obtained, without zero-point energy (ZPE) correction, which is consistent with experimental values obtained for substituted benzamidine. 59 The imaginary frequency at the global maximum is 126.9i cm −1 .…”

Section: Crystal Growth and Designmentioning

confidence: 95%

Occurence of Charge-Assisted Hydrogen Bonding in Bis-amidine Complexes Generating Macrocycles

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Hădade

Lee

et al. 2016

Crystal Growth & Design

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Bis-amidine and bis-carboxylate derivatives have been studied in this work to extend the knowledge of chargeassisted hydrogen bonding (CAHB) which counts among the strongest noncovalent bonding observed so far and arises from the combination of two well-identified types of interactions, namely, electrostatic attraction and hydrogen bonding. The formation of such bridges and the associated formation of macrocycles were screened for substituted (1) and nonsubstituted (2) bis-benzamidines through the use of isomeric proton acceptors aromatic bis-carboxylic (3−6) and bis-sulfonic acids (7−8). A library made from the combination of amidines and carboxylic/sulfonic acids was assessed both in solution and in the solid state. The formation of the CAHB motif was found to be highly dependent on the E,Z isomerization of the amidine moiety. Interesting double dipolar motifs were identified in the solid state.

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General and theoretical aspects of amidines and related compounds

Häfelinger

Kuske

1991

Amidines and Imidates (1991)

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Resonance magnetique dynamique du carbone I. Application a l'etude conformationnelle d'amidines substituees

Cited by 29 publications

References 13 publications

Noncovalent Interactions between Tetrazole and anN,N‘-Diethyl-Substituted Benzamidine

Noncovalent Interactions between Tetrazole and anN,N‘-Diethyl-Substituted Benzamidine

Occurence of Charge-Assisted Hydrogen Bonding in Bis-amidine Complexes Generating Macrocycles

General and theoretical aspects of amidines and related compounds

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