Hydrogen bonding in push-pull 5-substituted-2-alkylidene-4-oxothiazolidines: 1H-MNR spectroscopic study

Marković, Rade; Shirazi, Ata; Dzambaski, D Zdravko; Baranac, Marija; Minic-Popovic, M Dragica

doi:10.2298/jsc0301001m

Cited by 15 publications

(15 citation statements)

References 17 publications

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“…Gilli et al [14][15][16] proposed the concept of RAHBs, this has had great success in many fields such as organic chemistry, [17][18][19][20][21] infrared spectroscopy, 22 nuclear magnetic resonance, 23 electron diffraction, 24 or biological chemistry. [25][26][27][28] The proton donor and proton acceptor groups in RAHBs are connected through a chain of p-conjugated double bonds, and the standard explanation of the noticeable strength of these interactions is based on a chemically intuitive reasoning in which the conjugated bonds display an equalization of lengths through a pseudo-ring.…”

Section: Introductionmentioning

confidence: 99%

The nature of resonance-assisted hydrogen bonds: a quantum chemical topology perspective

Guevara‐Vela

Romero-Montalvo

Costales

et al. 2016

Phys. Chem. Chem. Phys.

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Title: The nature of resonance-assisted hydrogen bonds: a quantum chemical topology perspectiveThis work addresses the nature of Resonance Assisted Hydrogen Bonds (RAHBs) by considering malonaldehyde whose H-bonded (closed) and non H-bonded (open) conformations are represented in the bottom and top of the seesaws respectively. Although delocalization indices are more uniform in the closed form (seesaw in the left), the number of delocalized electrons diminish on RAHB formation. The interaction is characterized by an increase/decrease in the intra-atomic/inter-atomic exchange energies as schematized with sparks in the highlighted seesaw in the right. The artwork is due to Mr Víctor Duarte Alaniz. indicate that the p-conjugated bonds allow for a larger adjustment of electron density throughout the H-bonded system as compared with non-conjugated carbonyl molecules. This rearrangement of charge distribution is a response to the electric field due to the H atom involved in the hydrogen bonding of the considered compounds. As opposed to the usual description of RAHB interactions, these HBs lead to a larger electron localisation in the system, and concomitantly to larger QTAIM charges which in turn lead to stronger electrostatic, polarization and charge transfer components of the interaction. Overall, the results presented here offer a new perspective on the cause of strengthening of these important interactions.

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Section: Introductionmentioning

confidence: 99%

The nature of resonance-assisted hydrogen bonds: a quantum chemical topology perspective

Guevara‐Vela

Romero-Montalvo

Costales

et al. 2016

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

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“…The samples were equilibrated at the given temperatures. The 1 H NMR and 13 C NMR data of the configurational isomers (E)-9a and (Z)-9a, fully shown below, provide a fairly complete picture of this isomeric equilibrium. Monitoring of the stereodynamic behaviour associated with the isomerization rate of (E)-9a to (Z)-9a was performed in DMSO-d 6 solutions at 298, 303 and 308 K. The E/Z ratios were determined by the integration of the signals at d 5.64 and d 6.15 ppm, assigned to the C(2 0 )-H protons of (E)-9a and (Z)-9a, respectively.…”

Section: Methodsmentioning

confidence: 88%

“…Recent theoretical studies 10c,i have found that in a fragment shown in Scheme 3, these electronic interactions increase in the order: O o S. In the case of our stereodefined push-pull thiazolidine derivatives 1 (Scheme 1), the above mentioned electronic interactions, that occur here between two electron donors (N ring and S ring ) and one electron acceptor (R 1 CX; R 1 = Ph, OEt, NHPh, NH(CH 2 ) 2 Ph; X = O), have been evidenced by the facile Z/E configurational isomerization that takes place spontaneously in solution, at room temperature (Scheme 4). 11,13 The direction of this isomerization is dictated by solvent polarity. Polar solvents break the intramolecular hydrogen bonding in the E isomer and shift the equilibrium to the Z isomer, by forming stable solventsolute intermolecular interactions.…”

Section: Stereodynamic Behaviour Of 2-alkylidene-4-oxothiazolidine Dementioning

confidence: 99%

“…In addition to DG # , other parameters often used as a measure of the push-pull effect are: (i) 13 C NMR chemical shift difference Dd CQC between the two carbon atoms of the CQC double bond, 10b,e,g,i (ii) the bond length of the central partial CQC double bond, 10c,h experimentally available by X-ray analysis and (iii) the quotient of the occupation numbers of the p* antibonding and p bonding orbitals (p*/p) of the CQC double bond, available from theoretical calculations combined with Natural Bond Orbital (NBO) analysis. 10c,i Although the occupation quotient (p*/p) can be regarded as a sensitive parameter for quantification of the push-pull effect with a broader scope than the other quantities (DG # , Dd CQC and bond length), 10c,i a general parameter to quantify the push-pull effect is not yet available due to the (p*/p) parameter dependence on the type and number of substituents at the push-pull CQC double bond.…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly and surprisingly, [11][12][13][14] thiazolidine derivative 9a was isolated from the reaction mixture by filtration (ethanol solution) and recrystallized from 96% ethanol to provide a final product as the pure E isomer.…”

Section: Introductionmentioning

confidence: 99%

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Quantification of the push–pull effect in 2-alkylidene-4-oxothiazolidines by using NMR spectral data and barriers to rotation around the CC bond

et al. 2016

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Information about the strength of donor-acceptor interactions in push-pull alkenes is valuable, as this so-called ''push-pull effect'' influences their chemical reactivity and dynamic behaviour. In this paper, we discuss the applicability of NMR spectral data and barriers to rotation around the CQC double bond to quantify the push-pull effect in biologically important 2-alkylidene-4-oxothiazolidines. While olefinic proton chemical shifts and differences in 13 C NMR chemical shifts of the two carbons constituting the CQC double bond fail to give the correct trend in the electron withdrawing ability of the substituents attached to the exocyclic carbon of the double bond, barriers to rotation prove to be a reliable quantity in providing information about the extent of donor-acceptor interactions in the push-pull systems studied. In particular all relevant kinetic data, that is the Arrhenius parameters (apparent activation energy E a and frequency factor A) and activation parameters (DS ‡ , DH ‡ and DG ‡ ), were determined from the data of the experimentally studied configurational isomerization of (E)-9a. These results were compared to previously published related data for other two compounds, (Z)-1b and (2E,5Z)-7, showing that experimentally determined DG ‡ values are a good indicator of the strength of push-pull character. Theoretical calculations of the rotational barriers of eight selected derivatives excellently correlate with the calculated CQC bond lengths and corroborate the applicability of DG ‡ for estimation of the strength of the push-pull effect in these and related systems.

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One‐Pot Synthesis and Antiproliferative Activity of Highly Functionalized Pyrazole Derivatives

et al. 2022

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A series of highly functionalized pyrazole derivatives has been prepared by a one‐pot, versatile and regioselective procedure. Pyrazoles 1–29 were tested in cell‐based assay to assess their antiproliferative activity against a panel of tumour cells. Additionally, the cytotoxicity of prepared compounds was evaluated against normal human fibroblasts. The antiproliferative activity of the synthesized molecules emerged to be affected by the nature of the substituents of the pyrazole scaffold and derivatives 21–23 proved to inhibit the growth of melanoma and cervical cancer cells. Compound 23 was identified as the most active derivative and docking simulations predicted its ability to interact with estrogen receptors.

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Hydrogen bonding in push-pull 5-substituted-2-alkylidene-4-oxothiazolidines: 1H-MNR spectroscopic study

Cited by 15 publications

References 17 publications

The nature of resonance-assisted hydrogen bonds: a quantum chemical topology perspective

The nature of resonance-assisted hydrogen bonds: a quantum chemical topology perspective

Quantification of the push–pull effect in 2-alkylidene-4-oxothiazolidines by using NMR spectral data and barriers to rotation around the CC bond

One‐Pot Synthesis and Antiproliferative Activity of Highly Functionalized Pyrazole Derivatives

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