2033-45-6Relevant articles and documents
Hypervalent iodine in synthesis. 90. A mild and efficient method for the iodination of pyrazoles
Cheng, Dong-Ping,Chen, Zhen-Chu,Zheng, Qin-Guo
, p. 2671 - 2676 (2003)
The combined reagent of iodobenzene diacetate (or polymer-supported iodobenzene diacetate) with iodine was used as an effective iodinating agent of pyrazoles to the corresponding 4-iodopyrazole derivatives at room temperature with high yields.
1,1′-Bis(pyrazol-4-yl)ferrocenes: Potential Clip Ligands and Their Supramolecular Structures
Veronelli, Mattia,Dechert, Sebastian,Schober, Anne,Demeshko, Serhiy,Meyer, Franc
, p. 446 - 453 (2017)
Two ferrocene derivatives with pyrazoles appended at their C-4 position to both cyclopentadienyl (Cp) rings have been synthesized, namely, 1,1′-bis(1H-pyrazol-4-yl)ferrocene (H2HL) and 1,1′-bis(3,5-dimethyl-1H-pyrazol-4-yl)ferrocene (H2MeL). In the solid state, these are shown crystallographically to form supramolecular aggregates through intermolecular NH···N hydrogen bonds in either a dimeric (H2HL) or trimeric (H2MeL) arrangement. Variable-temperature NMR spectroscopy and diffusion-ordered spectroscopy (DOSY) evidenced the presence of [H2MeL]3trimers in [D8]toluene solution, whereas both H2HL and H2MeL exist as monomers in deuterated N,N-dimethylformamide ([D7]DMF) even at low temperatures. The kinetic parameters for the NH tautomerism have been determined. In their dianionic forms, both of these hybrid ferrocene/pyrazole molecules serve as ligands towards CuI, AgI, and AuIions. Matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) revealed the formation of [M2RL]3hexametallic complexes, the structures of which are suggested to have D3hsymmetry with two metallomacrocyclic [M(μ-pz)]3(pz = pyrazolate) decks connected by three ferrocene clips. M?ssbauer spectra and preliminary luminescence data were collected for the proligands and the resulting complexes. Owing to the insolubility of the coinage-metal complexes, the electrochemical properties could be measured only for the two H2RL proligands.
Predicting the catalytic activity of azolium-based halogen bond donors: an experimentally-verified theoretical study
Sysoeva, Alexandra A.,Novikov, Alexander S.,Il'in, Mikhail V.,Suslonov, Vitalii V.,Bolotin, Dmitrii S.
, p. 7611 - 7620 (2021/09/22)
This report demonstrates the successful application of electrostatic surface potential distribution analysis for evaluating the relative catalytic activity of a series of azolium-based halogen bond donors. A strong correlation (R2> 0.97) was observed between the positive electrostatic potential of the σ-hole on the halogen atom and the Gibbs free energy of activation of the model reactions (i.e., halogen abstraction and carbonyl activation). The predictive ability of the applied approach was confirmed experimentally. It was also determined that the catalytic activity of azolium-based halogen bond donors was generally governed by the structure of the azolium cycle, whereas the substituents on the heterocycle had a limited impact on the activity. Ultimately, this study highlighted four of the most promising azolium halogen bond donors, which are expected to exhibit high catalytic activity.
Deprotonation of 4-ethynylpyrazolium salts
Ahlburg, Nils Lennart,Doppleb, Olivia,Hillrichs, Kai,Namyslo, Jan C.,Hübner, Eike G.,Schmidt, Andreas
, p. 1203 - 1215 (2018/08/06)
4-Ethynyl-1,2-dimethylpyrazolium salts were prepared by methylation of the corresponding 4-ethynyl-1-methylpyrazoles with trimethyloxonium tetrafluoroborate and were deprotonated to give the corresponding pyrazolium-4acetylenides, which are mesomeric betaines. These can be represented as alkynyl- or mesoionic allenylidene-type resonance forms. Calculations and spectroscopic investigations were performed to determine the contribution of each canonical form to the overall structure. Ylides and N-heterocyclic carbenes are tautomers of the betaines. Their relative stabilities have been compared.
