Synthesis of pyrrole-fused dibenzoxazepine/dibenzothiazepine/triazolobenzodiazepine derivatives via isocyanide-based multicomponent reactions

• Marzieh Norouzi,
• Mohammad Taghi Nazeri,
• Ahmad Shaabani and
• Behrouz Notash

Beilstein J. Org. Chem. 2024, 20, 2870–2882, doi:10.3762/bjoc.20.241

• temperature (Figure 3A) [46]. Therefore, dynamic NMR measurements were performed for compound 6f at various temperatures (25, 35, 45, 55, 65, 75, and 85 °C). As illustrated in Figure 3, all peaks in the spectrum correspond to the structure of 6f. Spectrum A recoreded at 25 °C has two broad singulet signals at

Synthesis of purines and adenines containing the hexafluoroisopropyl group

• Viacheslav Petrov,
• Rebecca J. Dooley,
• Alexander A. Marchione,
• Elizabeth L. Diaz,
• Brittany S. Clem and
• William Marshall

Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224

• group in compounds 5a and 6a (see Table 2) because of the presence in the β-position relative to the CH(CF3)2 unit of the amino group, which is substantially bigger than a hydrogen atom. Dynamic NMR spectroscopy The broadening of resonances corresponding to the hexafluoroisopropyl moieties in the 19F

• referenced to internal tetramethylsilane or trichlorofluoromethane. The spectra were acquired at 298 K. Dynamic NMR experiments The dynamics of rotamer interconversion were studied on a Bruker AVIIIHD spectrometer with a 9.4 T magnetic field, equipped with a 10 mm F{H} probe suitable for high- and low

Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

• Camila B. Francisco,
• Cleverton S. Fernandes,
• Ulisses Z. de Melo,
• Roberto Rittner,
• Gisele F. Gauze and
• Ernani A. Basso

Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

• -iodocyclohexylamine (I) by dynamic NMR and theoretical calculations. The experimental data pointed to an equilibrium strongly shifted toward the ea conformer (equatorial amine group and axial halogen), with populations greater than 90% for F, Cl and Br in both dichloromethane-d2 and methanol-d4. Theoretical

• preference for the ea conformer in cis-2-halocyclohexylamines, being strong enough to restrain the shift in the equilibrium due to other factors such as steric repulsion or solvent effects. Keywords: conformational equilibrium; cyclohexane derivatives; dynamic NMR; hyperconjugation; principal component

• group and equatorial halogen) and ea (equatorial amine group and axial halogen) conformers (Figure 1) by dynamic NMR (DNMR) and theoretical calculations. Results and Discussion Experimental conformational population Low-temperature NMR experiments allow the identification of the individual conformers

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

One-pot three-component route for the synthesis of S-trifluoromethyl dithiocarbamates using Togni’s reagent

• Azim Ziyaei Halimehjani,
• Martin Dračínský and
• Petr Beier

Beilstein J. Org. Chem. 2017, 13, 2502–2508, doi:10.3762/bjoc.13.247

• DFT calculations. Figure 1 depicts variable temperature 1H NMR spectra of compound 4c. The coalescence of the methyl signals can be observed at 308 K, whereas the coalescence of the CH2 signals would require an even higher temperature than 328 K. Complete lineshape analysis approach (dynamic NMR, dNMR

Correction: Synthesis, dynamic NMR characterization and XRD studies of novel N,N’-substituted piperazines for bioorthogonal labeling

• Constantin Mamat,
• Marc Pretze,
• Matthew Gott and
• Martin Köckerling

Beilstein J. Org. Chem. 2017, 13, 301–302, doi:10.3762/bjoc.13.32

• : building blocks; coalescence; dynamic NMR; labeling; Staudinger ligation; In the original article an incorrect caption for Figure 1 was given. The assignment of the solvents to the capital letters was not correct. The correct caption of Figure 1 is: 1H NMR spectra of compound 3a measured in five different

Synthesis, dynamic NMR characterization and XRD studies of novel N,N’-substituted piperazines for bioorthogonal labeling

• Constantin Mamat,
• Marc Pretze,
• Matthew Gott and
• Martin Köckerling

Beilstein J. Org. Chem. 2016, 12, 2478–2489, doi:10.3762/bjoc.12.242

• applicability of these compounds as possible 18F-building blocks, two biomolecules were modified and chosen for conjugation either using the Huisgen-click reaction or the traceless Staudinger ligation. Keywords: building blocks; coalescence; dynamic NMR; labeling; Staudinger ligation; Introduction The

• 5a serve as starting material (precursor) whereas fluorine compounds 4b and 5b function as appendant reference compounds to analyze the prospective 18F-containing compounds. The reaction pathway for all piperazines is illustrated in Scheme 1. Dynamic NMR studies During the full characterization of

First chemoenzymatic stereodivergent synthesis of both enantiomers of promethazine and ethopropazine

• Paweł Borowiecki,
• Daniel Paprocki and
• Maciej Dranka

Beilstein J. Org. Chem. 2014, 10, 3038–3055, doi:10.3762/bjoc.10.322

• due to the following facts: (i) It has been empirically confirmed by Latypov et al. [76] (as a result of dynamic NMR studies) that a final prevalent conformation in the CDA-substrate system in the case of MPA esters of secondary alcohols renders the sp rotamer, in which the methoxy group, the Cα

An experimental and theoretical NMR study of NH-benzimidazoles in solution and in the solid state: proton transfer and tautomerism

• Carla I. Nieto,
• Pilar Cabildo,
• M. Ángeles García,
• Rosa M. Claramunt,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2014, 10, 1620–1629, doi:10.3762/bjoc.10.168

• four NH-benzimidazoles: 1 and 3 yielded average signals in DMSO-d6 and only in HMPA-d18 the prototropic exchange was slow, on the other hand 2 and 4 behaved as if the tautomerism was blocked in DMSO-d6. In the case of 1 a dynamic NMR (DNMR) study in HMPA-d18 was performed (Figure 6). The relevant data

Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

• Yuta Takano,
• Yuki Nagashima,
• M. Ángeles Herranz,
• Nazario Martín and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65

• spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures

• metallofullerene derivatives for the use in material science. Keywords: carbon nanomaterials; dynamic NMR; endofullerenes; La2@C80; La@C82; sultine; Introduction Endohedral metallofullerenes (EMFs) are a family of nanocarbons, which encapsulated one or more metal atoms inside a hollow carbon cage [1][2][3][4

Chromatographically separable rotamers of an unhindered amide

• Mario Geffe,
• Lars Andernach,
• Oliver Trapp and
• Till Opatz

Beilstein J. Org. Chem. 2014, 10, 701–706, doi:10.3762/bjoc.10.63

• pure form by crystallization. While Rice and Brossi focused on the optical and crystallographic properties of these compounds, Szántay et al. gave a first estimate of the activation energy of the interconversion of these two rotamers based on dynamic NMR spectroscopy at variable temperature. They

• deduced a value of 94 kJ/mol from a coalescence temperature of 170 °C but did not provide crucial data such as the spectrometer frequency required for the calculation. Sulima et al. reported a rotational barrier of 92 kJ/mol for 1-bromo-N-formyl-4-hydroxy-3-methoxymorphinan-6-one based on dynamic NMR

• quantitatively by refluxing 3 in ethyl formate (Scheme 1). Dynamic NMR (DNMR) measurements (400 MHz) on a sample of 4 in DMSO-d6 at temperatures ranging from 20 °C to 150 °C, the upper limit for technical reasons, showed no signs of beginning coalescence of the formyl proton resonances even at the highest

Structure of 1,5-benzodiazepinones in the solid state and in solution: Effect of the fluorination in the six-membered ring

• Marta Pérez-Torralba,
• Rosa M. Claramunt,
• M. Ángeles García,
• Concepción López,
• M. Carmen Torralba,
• M. Rosario Torres,
• Ibon Alkorta and
• José Elguero

Beilstein J. Org. Chem. 2013, 9, 2156–2167, doi:10.3762/bjoc.9.253

• studies at the B3LYP/6-311++G(d,p) level were carried out on these compounds and on four non-fluorinated derivatives, allowing to calculate geometries, tautomeric energies and ring-inversion barriers, that were compared with the experimental results obtained by static and dynamic NMR in solution and in

The chemistry of bisallenes

• Henning Hopf and
• Georgios Markopoulos

Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225

On the mechanism of action of gated molecular baskets: The synchronicity of the revolving motion of gates and in/out trafficking of guests

• Keith Hermann,
• Stephen Rieth,
• Hashem A. Taha,
• Bao-Yu Wang,
• Christopher M. Hadad and
• Jovica D. Badjić

Beilstein J. Org. Chem. 2012, 8, 90–99, doi:10.3762/bjoc.8.9

• the basket: Specifically, the greater the affinity of the guest for occupying the basket, the less effective the gates are in “sweeping” the guest as the gates undergo their revolving motion. Keywords: dynamic NMR; host–guest chemistry; linear free-energy relationships; molecular encapsulation

• ΔG‡rac (i.e., opening and closing, see below in Figure 6) reveals a systematic disparity (ΔG° + ΔG‡rac + ΔG‡sterics ≠ ΔG‡out, see below in Figure 7). In order to address this conundrum, we have employed methods of experimental (dynamic NMR) and computational chemistry (steered molecular dynamics, SMD

• rise to two enantiomeric conformers 1A and 1B (Figure 7A). The interconversion kinetics of the 1A/B racemization can be followed by dynamic NMR spectroscopy in which a singlet corresponding to Ha/Hb nuclei at high temperatures is seen to split into two doublets at low temperatures. In particular, the

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• points are incorporated by inserting building blocks bearing orthogonal amine functionalities at specific locations in the chain [86]. Conformational studies by dynamic NMR spectroscopy of β-(1→3)- and β-(1→6)-linked diglucosylthioureas (e.g. 41) detected the presence of Z,Z and Z,E conformers at the N

[3.3]Dithia-bridged cyclophanes featuring a thienothiophene ring: synthesis, structures and conformational analysis

• Sabir H. Mashraqui,
• Yogesh Sanghvikar,
• Shailesh Ghadhigaonkar,
• Sukeerthi Kumar,
• Auke Meetsma and
• Elise Trân Huu Dâu

Beilstein J. Org. Chem. 2009, 5, No. 74, doi:10.3762/bjoc.5.74

• ]dithia-bridged cyclophanes; dynamic NMR analysis; thieno[2,3-b]thiophene; X-ray crystal structure; Introduction The synthesis, molecular structures and conformational dynamics of short-bridged cyclophanes continue to engage interest in supramolecular chemistry [1][2][3][4]. The study of the