Azole, 26. Stellvertretende nucleophile Substitution von Wasserstoff in Nitropyrazolderivaten

Bernard, Marek K.; Szafran, Barbara; Wrzeciono, U.; Mąkosza, Mieczysław

doi:10.1002/jlac.198919890196

Cited by 27 publications

(9 citation statements)

References 16 publications

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“…1‐Methyl‐4‐nitropyrazole ( 7 ) was exclusively attacked at position 5 to give 5‐benzenesulfonylmethyl)‐1‐methyl‐4‐nitro‐1 H ‐pyrazole ( 7 o ) in 86 % yield (Scheme ), in analogy to previously reported reactions of 7 with other carbanions 27. 28 In contrast to the regioselectivity of the reaction of 5 a with 1 − (see above), 2‐nitrothiophene ( 8 ) is selectively attacked at the 3‐position by 1 − (Scheme ) 22.…”

Section: Resultssupporting

confidence: 61%

Reactions of Nitroheteroarenes with Carbanions: Bridging Aromatic, Heteroaromatic, and Vinylic Electrophilicity

Seeliger

Błażej

Bernhardt

et al. 2008

Chemistry A European J

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The relative rate constants for the vicarious nucleophilic substitution (VNS) of the anion of chloromethyl phenyl sulfone (1-) with a variety of nitroheteroarenes, for example, nitropyridines, nitropyrroles, nitroimidazoles, 2-nitrothiophene, and 4-nitropyrazole, have been determined by competition experiments. It was shown that nitropyridines are approximately four orders of magnitude more reactive than nitrobenzene. Among the five-membered heterocycles 2-nitrothiophene is the most active followed by nitroimidazoles and 4-nitropyrazole. Nitropyrroles are the least electrophilic nitroheteroarenes with reactivities comparable to nitrobenzene. Quantum chemically calculated methyl anion affinities (B3LYP/6-311G(d,p)//B3LYP/6-31G(d)) of the nitroarenes correlated only moderately with the partial relative rate constants. The correlation of these activities with the LUMO energies of nitroarenes is even worse. By measuring the second-order rate constants of the addition of 1- to nitroarenes and to diethyl arylidenemalonates 10, it was possible to link the electrophilic reactivities of nitroheteroarenes with the comprehensive electrophilicity scale based on the linear-free-energy-relationship log k(20 degrees C)=s(N+E).

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Section: Resultssupporting

confidence: 61%

Reactions of Nitroheteroarenes with Carbanions: Bridging Aromatic, Heteroaromatic, and Vinylic Electrophilicity

Seeliger

Błażej

Bernhardt

et al. 2008

Chemistry A European J

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“…A similar situation was observed during the reaction of 4-nitro-1-phenylimidazole and 2-methyl-1-phenyl-4-nitroimidazole with 4-amino-1,2,4-triazole in the MeONa-DMSO system [27,28], although in 4-nitropyrazole, which has a para-nitrophenyl substituent at position 1, vicarious nucleophilic substitution of hydrogen takes place both in the azole and in the arylene fragments [29].…”

Section: _______mentioning

confidence: 56%

Radical-anions in the vicarious C-amination reactions of N-substituted nitrotriazoles

Vakul’skaya

Titova

Ларина

et al. 2006

Chem Heterocycl Compd

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The constant attention of synthetic chemists to the vicarious nucleophilic substitution of hydrogen is reflected in a series of detailed reviews [1][2][3]. During the vicarious substitution of hydrogen an amino group is readily introduced into nitro aromatic and nitro heteroaromatic compounds [4,5], and this opens up broad synthetic possibilities (in particular the Sandmeyer reaction) and in itself explains the increased interest in the vicarious nucleophilic substitution of hydrogen. Interest has recently shifted to study of the mechanism of the process [6-9].Having put forward the idea of possible electron transfer during the vicarious nucleophilic substitution of hydrogen [9] and having confirmed this for the vicarious amination of nitrobenzene and a series of N-methylated nitroazoles [10-12], we assumed that the lower the reduction potential of the nitroazole the more readily the latter should undergo amination in the vicarious nucleophilic substitution of hydrogen. Our papers on the electrochemical reduction of azoles in an aprotic medium [13,14] show that their first reduction potentials decrease both with the accumulation of nitrogen atoms in the heterocycle and with the introduction of phenylene fragments. Apparently, overlap of the orbitals of the unshared electron pairs of adjacent pyridine nitrogen atoms or increase in the aromaticity of the system help to reduce the energy of the LUMO and facilitate the transfer of an electron to the molecule being reduced. _______ * Dedicated to Academician M. G. Voronkov on his 85th birthday. __________________________________________________________________________________________

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“…Starting materials 3, 4, and 5 were obtained according to known methods. 28,40,41 Moreover, values of chemical shifts were directly taken from FID files (ASCII files recorded in TopSpin), and all experiments were correctly calibrated. It is worth mentioning that the changes in chemical shifts were caused not by a potential field drift, but by the interactions of the analyte with environment.…”

Section: Discussionmentioning

confidence: 99%

Possible interactions between fused pyrazole derivative and magnesium ions - NMR experiments and theoretical calculations

Czaja¹,

Kujawski²,

Girreser³

et al. 2016

Arkivoc

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The paper verifies our recently described NMR approach for the determination of interaction sites between a heterocyclic ligand and magnesium ions. The method is based on the comparison of chemical shifts of condensed pyrazole derivative before and after the complexation with magnesium salt and is supported by DFT (B3LYP/6-31G(d,p) level of theory, CPCM solvation model, GIAO method) and classical molecular dynamics theoretical calculations.

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Azole, 26. Stellvertretende nucleophile Substitution von Wasserstoff in Nitropyrazolderivaten

Cited by 27 publications

References 16 publications

Reactions of Nitroheteroarenes with Carbanions: Bridging Aromatic, Heteroaromatic, and Vinylic Electrophilicity

Reactions of Nitroheteroarenes with Carbanions: Bridging Aromatic, Heteroaromatic, and Vinylic Electrophilicity

Radical-anions in the vicarious C-amination reactions of N-substituted nitrotriazoles

Possible interactions between fused pyrazole derivative and magnesium ions - NMR experiments and theoretical calculations

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