C-N coupling
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Urea stands as a vital industrial material with notable applications in energy and agriculture. However, the Haber-Bosch synthesis process, characterized by high energy consumption and emissions, poses significant challenges. Electrocatalytic C-N coupling offers a promising alternative but is constrained by the scarcity of efficient catalysts. In this work, Cr4/Ti2CO2 is emerged as an optimal candidate with a remarkable low overpotential of 0.29 V and a kinetic energy barrier of 0.40 eV. A comprehensive investigation into the influence of electrochemical potential on C-N coupling revealed that the d orbitals of active sites in different chemical environments within the clusters led to distinct hybridization mechanisms with the π* orbitals of adsorbed N2, which is defined as Mixed Cooperative Orbital Hybridization Mechanism. Specifically, the synergistic activation of the N≡N bond by the d(x2-y2) of top atom and the d-band center of bottom atoms determined the critical step C-N coupling energy barrier under electrode potential regulation. Additionally, Cr4/Ti2CO2 demonstrated optimal catalytic activity at a potential of 0.40 V versus the reversible hydrogen electrode (RHE) under acidic conditions (pH 0). These findings not only rationalize the design of an efficient electrocatalyst for urea synthesis but also elucidates the electronic mechanisms underlying potential-dependent catalytic activity.
- Klíčová slova
- C–N coupling, cluster modified MXene, density functional theory, potential‐dependent catalytic activity, urea synthesis,
- Publikační typ
- časopisecké články MeSH
2-Aroylmethylidene-1,2,3,4-tetrahydroquinolines with the appropriate substituents can be suitable precursors for the synthesis of alkaloids from Galipea officinalis (cuspareine, galipeine, galipinine, angustureine). However, only two, rather low-yielding procedures for their synthesis are described in the literature. We have developed a simple and efficient protocol for an intramolecular, palladium or copper-catalysed amination of both chloro- and bromo-substituted 3-amino-1,5-diphenylpent-2-en-1-ones leading to the above-mentioned tetrahydroquinoline moiety. The methodology is superior to the methods published to date.
- Klíčová slova
- C–N cross-coupling, copper, enaminone, palladium, tetrahydroquinoline,
- Publikační typ
- časopisecké články MeSH
A method for preparation of a new stable Cu(I) catalyst supported on weakly acidic polyacrylate resin without additional stabilizing ligands is described. A simple and efficient methodology for Ullmann Cu(I) catalyzed C-N cross coupling reactions using this original catalyst is reported. Coupling reactions of 4-chloropyridinium chloride with anilines containing electron donating (EDG) or electron withdrawing (EWG) groups, naphthalen-2-amine and piperazine, respectively, are successfully demonstrated.
- Klíčová slova
- C-N coupling, polymer solid support, recyclable green catalyst, supported Cu(I) catalyst,
- MeSH
- 2-naftylamin chemie MeSH
- akrylové pryskyřice chemie MeSH
- aniliny chemie MeSH
- elektrony * MeSH
- katalýza MeSH
- koncentrace vodíkových iontů MeSH
- měď chemie MeSH
- opakované použití vybavení MeSH
- piperazin MeSH
- piperaziny chemie MeSH
- pyridinové sloučeniny chemická syntéza MeSH
- technologie zelené chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- 2-naftylamin MeSH
- akrylové pryskyřice MeSH
- aniliny MeSH
- měď MeSH
- piperazin MeSH
- piperaziny MeSH
- pyridinové sloučeniny MeSH
The aim of this review is to summarize recent achievements in the field of (N),C,N-coordinated group 13-15 compounds not only regarding their synthesis and structure, but mainly focusing on their potential applications. Relevant compounds contain various types of N-coordinating ligands built up on an ortho-(di)substituted phenyl platform. Thus, group 13 and 14 derivatives were used as single-source precursors for the deposition of semiconducting thin films, as building blocks for the preparation of high-molecular polymers with remarkable optical and chemical properties or as compounds with interesting reactivity in hydrometallation processes. Group 15 derivatives function as catalysts in the Mannich reaction, in the allylation of aldehydes or activation of CO2 . They were used as transmetallation reagents in transition metal catalysed coupling reactions. The univalent species serve as ligands for transition metals, activate alkynes or alkenes and are utilized as catalysts in the transfer hydrogenation of azo-compounds.
- Klíčová slova
- (N),C,N chelating ligands, homogeneous catalysis, intramolecular interactions, main-group elements, metal-containing polymers.,
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
Novel practical methodology of synthesis of a several types of di-, tri-, and tetraarylpurine derivatives by a combination of regioselective Suzuki cross-coupling reactions and/or Cu-catalyzed N-arylation with direct C-H arylations was developed. 6,8-Diaryl- and 2,6,8-triaryl-9-isopropylpurines were prepared by one or two cross-couplings of 6-chloro- or 2,6-dichloro-9-isopropylpurine with arylboronic acids followed by Pd-catalyzed C-H arylation by aryl halides to position 8. 6-Chloropurine and adenine underwent Cu-catalyzed N-arylation to position 9 with boronic acids, followed by cross-coupling with AlMe3 and/or C-H arylation to obtain 8,9-diaryl-6-methylpurines or 8,9-diaryladenines (accompanied by products of partial N-arylation of adenine in position 6). The methodology is suitable for construction of small libraries of modified purines.
The catalytic versatility of cytochrome P450 monooxygenases is remarkable. Here, we present mechanistic and structural characterizations of TleB from Streptomyces blastmyceticus and its homolog HinD from Streptoalloteichus hindustanus, which catalyze unusual intramolecular C-N bond formation to generate indolactam V from the dipeptide N-methylvalyl-tryptophanol. In vitro analyses demonstrated that both P450s exhibit promiscuous substrate specificity, and modification of the N13-methyl group resulted in the formation of indole-fused 6/5/6 tricyclic products. Furthermore, X-ray crystal structures in complex with substrates and structure-based mutagenesis revealed the intimate structural details of the enzyme reactions. We propose that the generation of a diradical species is critical for the indolactam formation, and that the intramolecular C(sp2)-H amination is initiated by the abstraction of the N1 indole hydrogen. After indole radical repositioning and subsequent removal of the N13 hydrogen, the coupling of the properly-folded diradical leads to the formation of the C4-N13 bond of indolactam.
Based on the kinetics of interaction between a receptor and G-protein, a myriad of possibilities may result. Two extreme cases are represented by: 1/Collision coupling, where an agonist binds to the free receptor and then the agonist-receptor complex "collides" with the free G-protein. 2/Pre-coupling, where stable receptor/G-protein complexes exist in the absence of agonist. Pre-coupling plays an important role in the kinetics of signal transduction. Odd-numbered muscarinic acetylcholine receptors preferentially couple to G(q/11), while even-numbered receptors prefer coupling to G(i/o). We analyzed the coupling status of the various subtypes of muscarinic receptors with preferential and non-preferential G-proteins. The magnitude of receptor-G-protein coupling was determined by the proportion of receptors existing in the agonist high-affinity binding conformation. Antibodies directed against the C-terminus of the α-subunits of the individual G-proteins were used to interfere with receptor-G-protein coupling. Effects of mutations and expression level on receptor-G-protein coupling were also investigated. Tested agonists displayed biphasic competition curves with the antagonist [(3)H]-N-methylscopolamine. Antibodies directed against the C-terminus of the α-subunits of the preferential G-protein decreased the proportion of high-affinity sites, and mutations at the receptor-G-protein interface abolished agonist high-affinity binding. In contrast, mutations that prevent receptor activation had no effect. Expression level of preferential G-proteins had no effect on pre-coupling to non-preferential G-proteins. Our data show that all subtypes of muscarinic receptors pre-couple with their preferential classes of G-proteins, but only M(1) and M(3) receptors also pre-couple with non-preferential G(i/o) G-proteins. Pre-coupling is not dependent on agonist efficacy nor on receptor activation. The ultimate mode of coupling is therefore dictated by a combination of the receptor subtype and the class of G-protein.
- MeSH
- CHO buňky MeSH
- Cricetulus MeSH
- guanosin 5'-O-(3-thiotrifosfát) metabolismus MeSH
- karbachol metabolismus MeSH
- kinetika MeSH
- kompetitivní vazba MeSH
- křečci praví MeSH
- lidé MeSH
- mutace MeSH
- N-methylskopolamin metabolismus MeSH
- proteiny vázající GTP metabolismus MeSH
- receptory muskarinové genetika metabolismus MeSH
- zvířata MeSH
- Check Tag
- křečci praví MeSH
- lidé MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Research Support, N.I.H., Extramural MeSH
- Názvy látek
- guanosin 5'-O-(3-thiotrifosfát) MeSH
- karbachol MeSH
- N-methylskopolamin MeSH
- proteiny vázající GTP MeSH
- receptory muskarinové MeSH
This paper presents a measurement of the inclusive 3-jet production differential cross section at a proton-proton centre-of-mass energy of 7 TeV using data corresponding to an integrated luminosity of 5[Formula: see text]collected with the CMS detector. The analysis is based on the three jets with the highest transverse momenta. The cross section is measured as a function of the invariant mass of the three jets in a range of 445-3270 GeV and in two bins of the maximum rapidity of the jets up to a value of 2. A comparison between the measurement and the prediction from perturbative QCD at next-to-leading order is performed. Within uncertainties, data and theory are in agreement. The sensitivity of the observable to the strong coupling constant [Formula: see text] is studied. A fit to all data points with 3-jet masses larger than 664 GeV gives a value of the strong coupling constant of [Formula: see text].
- Klíčová slova
- 3-jet mass, Alpha-S, CMS, Jets, PDF, Physics, QCD, Strong coupling constant,
- Publikační typ
- časopisecké články MeSH
Reduction of C,N-chelated chloroborane [2-(CH=NtBu)C6H4]BPhCl () with the potassium metal afforded (3,3')-bis(1-Ph-2-tBu-1H-2,1-benzazaborole) (2). Compound 2 is formed via C-C reductive coupling reaction. Subsequent reduction of 2 with two equivalents of the potassium metal produced orange crystals of 1Ph-2tBu-1H-2,1-benzazaborolyl (Bab) potassium salt K(THF)(Bab) (3). Compound 3 is able to react with simple electrophiles (MeI or Me3SiCl) resulting in the formation of substituted 1H-2,1-benzazaboroles.
- Publikační typ
- časopisecké články MeSH
The electrochemical activity of modern Fe-N-C electrocatalysts in alkaline media is on par with that of platinum. For successful application in fuel cells (FCs), however, also high durability and longevity must be demonstrated. Currently, a limited understanding of degradation pathways, especially under operando conditions, hinders the design and synthesis of simultaneously active and stable Fe-N-C electrocatalysts. In this work, using a gas diffusion electrode half-cell coupled with inductively coupled plasma mass spectrometry setup, Fe dissolution is studied under conditions close to those in FCs, that is, with a porous catalyst layer (CL) and at current densities up to -125 mA·cm-2. Varying the rate of the oxygen reduction reaction (ORR), we show a remarkable linear correlation between the Faradaic charge passed through the electrode and the amount of Fe dissolved from the electrode. This finding is rationalized assuming that oxygen reduction and Fe dissolution reactions are interlinked, likely through a common intermediate formed during the Fe redox transitions in Fe species involved in the ORR, such as FeNxCy and Fe3C@N-C. Moreover, such a linear correlation allows the application of a simple metric─S-number─to report the material's stability. Hence, in the current work, a powerful tool for a more applied stability screening of different electrocatalysts is introduced, which allows on the one hand fast performance investigations under more realistic conditions, and on the other hand a more advanced mechanistic understanding of Fe-N-C degradation in CLs.
- Publikační typ
- časopisecké články MeSH
