Conformational behaviour and / isomerization of -acyl and -aroylhydrazones

Palla, Gerardo; Predieri, Giovanni; Domiano, P.; Vignali, Carlo; Turner, Walter V.

doi:10.1016/s0040-4020(01)87332-4

Cited by 239 publications

(226 citation statements)

References 5 publications

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“…However, starting from the pyridine-2-carboxaldehyde, the Z isomer can be detected in less polar solvents due to its stabilization with intramolecular H-bonds [5]. On the other hand, the duplication of NMR signals has been attributed to the presence of anti-and synperiplanar conformers in benzyl and alkyl NAHs [8][9][10], but there is no description of this phenomenon in aryl NAHs in the literature.…”

Section: Scheme 1 General Structure and Stereochemistry Of Nahmentioning

confidence: 99%

“…Because of the assemblage of amide and imine functions, NAH compounds may exist as C=N double bond stereoisomers (E/Z) (Scheme 1) and as syn/antiperiplanar conformers about the amide CO-NH bond (Scheme 1) [5].…”

Section: Introductionmentioning

confidence: 99%

“…Another approach used to evaluate the presence of two conformers was the synthesis of isopropylidene hydrazones. The latter was based on the works of Wyrzykiewicz and Prukala [27] and Palla [5], to eliminate the possibility of forming E/Z stereoisomers. The compound (isopropylidene)-2-phenyl-4-methyl-pyrimidine-5-hydrazide (12) (Figure 6) was synthesized by condensation of 2-phenyl-4-methyl-pyrimidine-5-hydrazide (11a) with acetone.…”

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confidence: 99%

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Characterization of Amide Bond Conformers for a Novel Heterocyclic Template of N-acylhydrazone Derivatives

et al. 2013

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Herein we describe NMR experiments and structural modifications of 4-methyl-2-phenylpyrimidine-N-acylhydrazone compounds (aryl-NAH) in order to discover if duplication of some signals in their 1 H-and 13 C-NMR spectra was related to a mixture of imine double bond stereoisomers (E/Z) or CO-NH bond conformers (syn and anti-periplanar). NMR data from NOEdiff, 2D-NOESY and 1 H-NMR spectra at different temperatures, and also the synthesis of isopropylidene hydrazone revealed the nature of duplicated signals of a 4-methyl-2-phenylpyrimidine-N-acylhydrazone derivative as a mixture of two conformers in solution. Further we investigated the stereoelectronic influence of substituents at the ortho position on the pyrimidine ring with respect to the carbonyl group, as well as the OPEN ACCESSMolecules 2013, 18 11684 electronic effects of pyrimidine by changing it to phenyl. The conformer equilibrium was attributed to the decoplanarization of the aromatic ring and carbonyl group (generated by an ortho-alkyl group) and/or the electron withdrawing character of the pyrimidine ring. Both effects increased the rotational barrier of the C-N amide bond, as verified by the ΔG ≠ values calculated from dynamic NMR. As far as we know, it is the first description of aryl-NAH compounds presenting two CO-NH bond-related conformations.

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Section: Scheme 1 General Structure and Stereochemistry Of Nahmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Characterization of Amide Bond Conformers for a Novel Heterocyclic Template of N-acylhydrazone Derivatives

et al. 2013

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“…The 1 H NMR spectra of most compounds display two sets of methylene, imine and amide proton signals, indicating that both cis and trans amide conformers were formed. It is known from conventional synthesis that the cis isomer is formed in excess (Palla et al, 1986). It is expected that the cis isomers of 4a should be due to the formation of an intramolecular hydrogen bond (Cordier et al, 2004).…”

Section: Resultsmentioning

confidence: 99%

An expendient method for the synthesis of bis(acylhydrazones) under microwave irradiation in solvent-free medium

Zheng

Zhu

et al. 2007

Braz. J. Chem. Eng.

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“…It is known that N-acylhydrazones can exist in four possible forms, as geometrical isomers (E/Z) with respect to the C=N double bond and as rotamers (cis/trans) due to the amide N-C(O) bond [24]. Based on literature data the N-acylhydrazones derived from aromatic aldehydes are in the E form because the ZN-N conformer is not formed due to the steric hindrance on the imine bond [25]. All compounds were found to exist as racemic mixtures of two isomers, as indicated by their 1 H-NMR spectra.…”

Section: Chemistrymentioning

confidence: 99%

Synthesis and Biological Evaluation of New 1,3-Thiazolidine-4-one Derivatives of 2-(4-Isobutylphenyl)propionic Acid

et al. 2014

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New thiazolidine-4-one derivatives of 2-(4-isobutylphenyl)propionic acid (ibuprofen) have been synthesized as potential anti-inflammatory drugs. The structure of the new compounds was proved using spectral methods (FR-IR, 1 H-NMR, 13 C-NMR, MS). The in vitro antioxidant potential of the synthesized compounds was evaluated according to the total antioxidant activity, the DPPH and ABTS radical scavenging assays. Reactive oxygen species (ROS) and free radicals are considered to be involved in many pathological events like diabetes mellitus, neurodegenerative diseases, cancer, infections and more recently, in inflammation. It is known that overproduction of free radicals may initiate and amplify the inflammatory process via upregulation of genes involved in the production of proinflammatory cytokines and adhesion molecules. The chemical modulation of acyl hydrazones of ibuprofen 3a-l through cyclization to the corresponding thiazolidine-4-ones 4a-n led to increased antioxidant potential, as all thiazolidine-4-ones were more active than their parent acyl hydrazones and also ibuprofen. The most active compounds are the thiazolidine-4-ones 4e, m, which showed the highest DPPH radical scavenging ability, their activity being comparable with vitamin E.

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Conformational behaviour and / isomerization of -acyl and -aroylhydrazones

Cited by 239 publications

References 5 publications

Characterization of Amide Bond Conformers for a Novel Heterocyclic Template of N-acylhydrazone Derivatives

Characterization of Amide Bond Conformers for a Novel Heterocyclic Template of N-acylhydrazone Derivatives

An expendient method for the synthesis of bis(acylhydrazones) under microwave irradiation in solvent-free medium

Synthesis and Biological Evaluation of New 1,3-Thiazolidine-4-one Derivatives of 2-(4-Isobutylphenyl)propionic Acid

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