Dynamic 1H NMR spectroscopic study of hindered internal rotation in selected N,N-dialkyl isonicotinamides: an experimental and DFT analysis

“…In general, this behavior of symmetric N,N-dialkylamide spin systems is describable as rst-order process on the NMR time scale. 41 The second effect is related to the hindered interconversion of the two piperazine ring chair conformations (Fig. 1, bottom).…”

Section: Mono-substituted Piperazinesmentioning

confidence: 99%

NMR-based investigations of acyl-functionalized piperazines concerning their conformational behavior in solution

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Two distinct signals are observed in the 1 H NMR spectrum of DMF as a result of two structurally different methyl groups (R 1 ≠ R 2 ) attached to the amide nitrogen [18–19]. In general, this behavior of symmetric N , N -dialkylamide spin systems is describable as first-order process on the NMR time scale [20]. …”

Section: Resultsmentioning

confidence: 99%

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

Mamat

Pretze

Gott

et al. 2016

Beilstein J. Org. Chem.

View full text Add to dashboard Cite

Novel, functionalized piperazine derivatives were successfully synthesized and fully characterized by 1H/13C/19F NMR, MS, elemental analysis and lipophilicity. All piperazine compounds occur as conformers resulting from the partial amide double bond. Furthermore, a second conformational shape was observed for all nitro derivatives due to the limited change of the piperazine chair conformation. Therefore, two coalescence points were determined and their resulting activation energy barriers were calculated using 1H NMR. To support this result, single crystals of 1-(4-nitrobenzoyl)piperazine (3a, monoclinic, space group C2/c, a = 24.587(2), b = 7.0726(6), c = 14.171(1) Å, β = 119.257(8)°, V = 2149.9(4) Å3, Z = 4, D obs = 1.454 g/cm3) and the alkyne derivative 4-(but-3-yn-1-yl)-1-(4-fluorobenzoyl)piperazine (4b, monoclinic, space group P21/n, a = 10.5982(2), b = 8.4705(1), c = 14.8929(3) Å, β = 97.430(1)°, V = 1325.74(4) Å3, Z = 4, D obs = 1.304 g/cm3) were obtained from a saturated ethyl acetate solution. The rotational conformation of these compounds was also verified by XRD. As proof of concept for future labeling purposes, both nitropiperazines were reacted with [18F]F–. To test the 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.

show abstract

“…As a result, three rotamers along the amide bonds ( A – C ) ( Figure 3 ), differing in the orientation of -CHCF 3 fragments relative to the phenanthroline backbone, which coexist in solutions, give separate signals in the NMR spectra. Note that processes of this type in arylcarboxamides are well documented [ 31 , 32 , 33 , 34 ]. In contrast to symmetric structures A and C , the rotamer B contains two non-equivalent CF 3 -groups in the structure.…”

Section: Resultsmentioning

confidence: 99%

First Trifluoromethylated Phenanthrolinediamides: Synthesis, Structure, Stereodynamics and Complexation with Ln(III)

et al. 2022

View full text Add to dashboard Cite

The first examples of 1,10-phenanthroline-2,9-diamides bearing CF3-groups on the side amide substituents were synthesized. Due to stereoisomerism and amide rotation, such complexes have complicated behavior in solutions. Using advanced NMR techniques and X-ray analysis, their structures were completely elucidated. The possibility of the formation of complex compounds with lanthanoids nitrates was shown, and the constants of their stability are quantified. The results obtained are explained in terms of quantum-chemical calculations.

show abstract

Dynamic 1H NMR spectroscopic study of hindered internal rotation in selected N,N-dialkyl isonicotinamides: an experimental and DFT analysis

Cited by 17 publications

References 70 publications

NMR-based investigations of acyl-functionalized piperazines concerning their conformational behavior in solution

NMR-based investigations of acyl-functionalized piperazines concerning their conformational behavior in solution

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

First Trifluoromethylated Phenanthrolinediamides: Synthesis, Structure, Stereodynamics and Complexation with Ln(III)

Contact Info

Product

Resources

About