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https://www.readbyqxmd.com/read/28636753/stable-bromiranium-ions-with-weakly-coordinating-counterions-as-efficient-electrophilic-brominating-agents
#1
Christoph Ascheberg, Jonathan Bock, Florenz Buß, Christian Mück-Lichtenfeld, Constantin B Daniliuc, Klaus Bergander, Fabian Dielmann, Ulrich Hennecke
Electrophilic halogenating agents are an important class of reagents in chemical synthesis. Herein, we show that sterically demanding bromiranium ions with weakly coordinating counterions are highly reactive electrophilic brominating agents. Despite their high reactivity these reagents are stable, in one case even under ambient conditions and can be applied in electrophilic halogenations of alkenes as well as heteroatoms.
June 21, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28636313/iodine-iii-reagents-in-radical-chemistry
#2
Xi Wang, Armido Studer
The chemistry of hypervalent iodine(III) compounds has gained great interest over the past 30 years. Hypervalent iodine(III) compounds show valuable ionic reactivity due to their high electrophilicity but also express radical reactivity as single electron oxidants for carbon and heteroatom radical generation. Looking at ionic chemistry, these iodine(III) reagents can act as electrophiles to efficiently construct C-CF3, X-CF3 (X = heteroatom), C-Rf (Rf = perfluoroalkyl), X-Rf, C-N3, C-CN, S-CN, and C-X bonds...
June 21, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28636265/switch-of-c-h-activation-mechanism-for-full-selectivity-control-in-cobalt-iii-catalyzed-c-h-alkylations
#3
Daniel Zell, Markus Bursch, Valentin Müller, Stefan Grimme, Lutz Ackermann
Selectivity control in hydroarylation-based C-H alkylation has been dominated by steric interactions. In contrast, we unravel a conceptually distinct strategy that exploits the programmed switch in the C-H activation mechanism by means of cobalt catalysis, setting the stage for expedient C-H alkylations with unactivated alkenes. Detailed mechanistic studies provided compelling evidence for a programmable switch in the C-H activation mechanism from a linear-selective ligand-to-ligand hydrogen transfer (LLHT) to a branched-selective base-assisted internal electrophilic-type substitution (BIES)...
June 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28634828/donation-and-back-donation-analyzed-through-a-charge-transfer-model-based-on-density-functional-theory
#4
Ulises Orozco-Valencia, José L Gázquez, Alberto Vela
The net charge transfer process that occurs between two species, A and B, interacting with each other, may be decomposed into two processes: one in which A receives charge from B, which can be identified as the electrophilic channel for A or the nucleophilic channel for B, and a second in which A donates charge to B, which can be identified as the nucleophilic channel for A or the electrophilic channel for B. By determining the amount of charge associated with both processes through the minimization of the interaction energy associated with each case, the expressions for the amount of charge involved in each case can be expressed in terms of the directional chemical potentials and the hardnesses of the interacting species...
July 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28632392/lewis-acid-promoted-hydrogenation-of-co2-and-hcoo-by-amine-boranes-mechanistic-insight-from-computational-approach
#5
Lisa Roy, Boyli Ghosh, Ankan Paul
We employ quantum chemical calculations to study the hydrogenation of carbon dioxide by amine-boranes, NMe3BH3 ((Me3)AB) and NH3BH3 (AB) weakly bonded to a bulkier Lewis acid, Al(C6F5)3 (LA). Additionally, computations has also been conducted to elucidate the mechanism of hydrogenation of carbon dioxide by (Me3)AB while captured between one Lewis Base (P(o-tol3), (LB)) and two Lewis acids, Al(C6F5)3. In agreement to the experiments, our computational study predicts that hydride transfer to conjugated HCO2(‒), generated in the reaction of (Me3)AB-LA with CO2, is not feasible...
June 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28632273/a-model-for-c-f-activation-by-electrophilic-phosphonium-cations
#6
Ian Mallov, Timothy C Johnstone, Darcy C Burns, Douglas W Stephan
The synthesis of the electrophilic phosphonium cation (EPC) salt [C10H6(CF3)PF(C6F5)2][B(C6F5)4] 4 was achieved via oxidation of phosphine [C10H6(CF3)P(C6F5)2] 2 with XeF2 to form phosphorane [C10H6(CF3)PF2(C6F5)2] 3 and subsequent fluoride ion abstraction. Structural and spectroscopic characterization of 4 provides evidence of an interaction between the CF3 functionality and the phosphonium centre. AIM and NBO analyses also support donation from a lone pair on a fluorine atom of the CF3 group to the P-F σ* orbital of the fluorophosphonium unit, consistent with previously proposed mechanisms for main group C-F bond activations...
June 20, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28631488/synthesis-of-6-7-dideoxysqualestatin-h5-by-carbonyl-ylide-cycloaddition-rearrangement-and-cross-electrophile-coupling
#7
Younes Fegheh-Hassanpour, Tanzeel Arif, Herman O Sintim, Hamad H Al Mamari, David M Hodgson
An asymmetric synthesis of (-)-6,7-dideoxysqualestatin H5 is reported. Key features of the synthesis include the following: (1) highly diastereoselective n-alkylation of a tartrate acetonide enolate and subsequent oxidation-hydrolysis to provide an asymmetric entry to a β-hydroxy-α-ketoester motif; (2) facilitation of Rh(II)-catalyzed cyclic carbonyl ylide formation-cycloaddition by co-generation of keto and diazo functionality through ozonolysis of an unsaturated hydrazone; and (3) stereoretentive Ni-catalyzed Csp(3)-Csp(2) cross-electrophile coupling between tricarboxylate core and unsaturated side chain to complete the natural product...
June 20, 2017: Organic Letters
https://www.readbyqxmd.com/read/28629590/bulky-dna-adducts-tobacco-smoking-genetic-susceptibility-and-lung-cancer-risk
#8
Armelle Munnia, Roger W Giese, Simone Polvani, Andrea Galli, Filippo Cellai, Marco E M Peluso
The generation of bulky DNA adducts consists of conjugates formed between large reactive electrophiles and DNA-binding sites. The term "bulky DNA adducts" comes from early experiments that employed a (32)P-DNA postlabeling approach. This technique has long been used to elucidate the association between adducts and carcinogen exposure in tobacco smoke studies and assess the predictive value of adducts in cancer risk. Molecular data showed increased DNA adducts in respiratory tracts of smokers vs nonsmokers. Experimental studies and meta-analysis demonstrated that the relationship between adducts and carcinogens was linear at low doses, but reached steady state at high exposure, possibly due to metabolic and DNA repair pathway saturation and increased apoptosis...
2017: Advances in Clinical Chemistry
https://www.readbyqxmd.com/read/28629263/mass-spectrometry-based-analysis-of-murine-bronchoalveolar-lavage-fluid-following-respiratory-exposure-to-4-4-methylene-diphenyl-diisocyanate-aerosol
#9
Justin M Hettick, Brandon F Law, Chen-Chung Lin, Adam V Wisnewski, Paul D Siegel
Diisocyanates are highly reactive electrophiles utilized in the manufacture of a wide range of polyurethane products, and have been identified as causative agents of occupational allergic respiratory disease. However, in spite of the significant occupational health burden associated with diisocyanate-induced asthma, the mechanism of disease pathogenesis remains largely unknown. To better understand the fate of inhaled diisocyanates, a nose-only aerosol exposure system was constructed and utilized to expose a BALB/c mouse model to aerosol generated from 4,4'-methylene diphenyl diisocyanate (MDI)...
June 20, 2017: Xenobiotica; the Fate of Foreign Compounds in Biological Systems
https://www.readbyqxmd.com/read/28628631/computational-explanation-for-bioactivation-mechanism-of-targeted-anticancer-agents-mediated-by-cytochrome-p450s-a-case-of-erlotinib
#10
Chun-Zhi Ai, Yong Liu, Wei Li, De-Meng Chen, Xin-Xing Zhu, Ya-Wei Yan, Du-Chu Chen, Yi-Zhou Jiang
EGFR inhibitors, even with therapeutics superiorities in anticancer, can cause idiosyncratic pulmonary and hepatic toxicities that are associated with the reactive electrophile bioactivated by Cytochrome P450s (P450s). Until now, neither has the electrophilic intermediate been caught experimentally, nor has the subtle mechanism been declared. Herein, the underlying mechanism of bioactivation mediated by P450s was explored by DFT calculations for a case of EGFR inhibitor, Erlotinib. Based on the calculation and analysis, we suggest that with other metabolites, reactive electrophiles of Erlotinib: epoxide and quinine-imine, can be generated by several steps along the oxidative reaction pathway...
2017: PloS One
https://www.readbyqxmd.com/read/28628319/on-the-mechanism-of-phenol-alkylation-in-zeolite-h-bea-using-in-situ-solid-state-nmr-spectroscopy
#11
Zhenchao Zhao, Hui Shi, Chuan Wan, Mary Y Hu, Yuanshuai Liu, Donghai Mei, Donald M Camaioni, Jian Zhi Hu, Johannes A Lercher
The reaction mechanism of solid-acid-catalyzed phenol alkylation with cyclohexanol and cyclohexene in the apolar solvent decalin has been studied using in situ (13)C MAS NMR spectroscopy. Phenol alkylation with cyclohexanol sets in only after a majority of cyclohexanol is dehydrated to cyclohexene. As phenol and cyclohexanol show similar adsorption strength, this strict reaction sequence is not caused by the limited access of phenol to cyclohexanol, but is due to the absence of a reactive electrophile as long as a significant fraction of cyclohexanol is present...
June 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28627560/asymmetric-tandem-conjugate-addition-protonation-to-forge-chiral-secondary-c-o-bonds-for-quaternary-carbon-stereocenters-at-the-nonadjacent-%C3%AE-position
#12
San-Ni Hong, Yang Liu, Richmond Lee, Zhiyong Jiang
A direct strategy to construct chiral secondary C-O bonds for quaternary carbon stereocenters at the nonadjacent β-position is described. Methylene 1,3-oxazolidine-2,4-diones were for the first time employed in an asymmetric reaction as viable electrophiles undergoing a tandem conjugate addition-protonation process. Using an l-amino acid-based urea-tertiary amine catalyst, the reaction with 3-substituted oxindoles gave valuable protonation adducts featuring 1,3-quaternary-tertiary (C-O) nonadjacent stereocenters in high yields and excellent stereoselectivities...
June 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28624702/evaluation-of-the-antidepressant-therapeutic-potential-of-isocyanine-and-pseudoisocyanine-analogues-of-the-organic-cation-decynium-22
#13
Anwen M Krause-Heuer, Rheaclare Fraser-Spears, Jeremy C Dobrowolski, Mark E Ashford, Naomi A Wyatt, Maxine P Roberts, Georgianna G Gould, Wai-Ching Cheah, Clarissa K L Ng, Mohan Bhadbhade, Bo Zhang, Ivan Greguric, Nial J Wheate, Naresh Kumar, Wouter Koek, Paul D Callaghan, Lynette C Daws, Benjamin H Fraser
Herein we describe the synthesis and evaluation of antidepressant properties of seven analogues (1-7) of the low affinity/high capacity transporter blocker decynium-22 (D-22). All analogues (1-7) were synthesized via base promoted coupling reactions between N-alkylated-2-methylquinolinium iodides or N-alkylated-4-methylquinolinium iodides and electrophilic N-alkylated-2-iodoquinolinium iodides. All final compounds were purified by re-crystallization or preparative HPLC and initial evaluation studies included; 1) screening for in vitro α1-adrenoceptor activity (a property that can lead to unwanted side-effects), 2) measuring antidepressant-like activity in a mouse tail suspension test (TST), and 3) measuring effects upon mouse locomotion...
June 7, 2017: European Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28623374/nucleotide-based-covalent-inhibitors-of-kras-can-only-be-efficient-in-vivo-if-they-bind-reversibly-with-gtp-like-affinity
#14
Matthias P Müller, Sadasivam Jeganathan, Angelika Heidrich, Jeremy Campos, Roger S Goody
Simple reversible competitive inhibition of nucleotide binding of GTP to Ras family GTPases has long been recognized as an unlikely approach to manipulating the activity of such proteins for experimental or therapeutic purposes. This is due to the high affinity of GTP to GTPases coupled with high cellular GTP concentrations, but also to problems of specificity for the highly conserved binding sites in GTPases. A recent approach suggested that these problems might be overcome by using GDP derivatives that can undergo a covalent reaction with disease specific mutants, in particular addressing inhibition of KRasG12C using GDP equipped with an electrophilic group at the β-phosphate...
June 16, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28621541/expanding-the-scope-of-electrophiles-capable-of-targeting-k-ras-oncogenes
#15
Lynn M McGregor, Meredith L Jenkins, Caitlin Kerwin, John E Burke, Kevan M Shokat
There is growing interest in reversible and irreversible covalent inhibitors that target noncatalytic amino acids in target proteins. With a goal of targeting oncogenic K-Ras variants (e.g., G12D) by expanding the types of amino acids that can be targeted by covalent inhibitors, we survey a set of electrophiles for their ability to label carboxylates. We functionalized an optimized ligand for the K-Ras switch II pocket with a set of electrophiles previously reported to react with carboxylates and characterized the ability of these compounds to react with model nucleophiles and oncogenic K-Ras proteins...
June 16, 2017: Biochemistry
https://www.readbyqxmd.com/read/28621380/theoretical-investigation-of-electrophilic-transannular-addition-reactions-of-bromine-to-face-to-face-juxtaposed-double-bonds-in-strained-polycyclic-hydrocarbons
#16
Rza Abbasoglu
Transannular electrophilic addition reaction of halogens to face-to-face(juxtaposed) double bonded strained alkenes were theoretically investigated. General rules that allow us to stipulate the factors that direct the main steps of the energy hypersurface of reactions as well as the products were established. Direction of the reaction flow is determined by direction of intramolecular skeletal isomerisation of cyclic-bridged halogenium cation and isomerisation takes place to create a more stable skeletal structure...
June 2017: Acta Chimica Slovenica
https://www.readbyqxmd.com/read/28621137/enantioselective-copper-catalyzed-oxy-alkynylation-of-diazo-compounds
#17
Durga Prasad Hari, Jerome Waser
Enantioselective catalytic methods allowing the addition of both a nucleophile and an electrophile onto diazo com-pounds give a fast access into important building blocks. Herein, we report the highly enantioselective oxyalkynyla-tion of diazo compounds using ethynylbenziodoxol-(on)e (EBX) reagents and a simple copper bisoxazoline (BOX) cat-alyst. The obtained -benzoyloxy propargylic esters are useful building blocks, which are difficult to synthesize in enantiopure form using other methods. The obtained prod-ucts could be efficiently transformed into vicinal diols and α-hydroxy propargylic esters without loss in enantiopurity...
June 16, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28620367/mycobacterial-f420h2-dependent-reductases-promiscuously-reduce-diverse-compounds-through-a-common-mechanism
#18
Chris Greening, Thanavit Jirapanjawat, Shahana Afroze, Blair Ney, Colin Scott, Gunjan Pandey, Brendon M Lee, Robyn J Russell, Colin J Jackson, John G Oakeshott, Matthew C Taylor, Andrew C Warden
An unusual aspect of actinobacterial metabolism is the use of the redox cofactor F420. Studies have shown that actinobacterial F420H2-dependent reductases promiscuously hydrogenate diverse organic compounds in biodegradative and biosynthetic processes. These enzymes therefore represent promising candidates for next-generation industrial biocatalysts. In this work, we undertook the first broad survey of these enzymes as potential industrial biocatalysts by exploring the extent, as well as mechanistic and structural bases, of their substrate promiscuity...
2017: Frontiers in Microbiology
https://www.readbyqxmd.com/read/28620120/ethyl-vanillin-activates-trpa1
#19
Shaw-Wen Wu, Daniel K Fowler, Forrest J Shaffer, Jonathon E M Lindberg, James Henry Peters
The non-selective cation channel TRPA1 is expressed in neurons of dorsal root ganglia and trigeminal ganglia and also in vagal afferent neurons that innervate the lungs and gastrointestinal tract. Many TRPA1 agonists are also reactive electrophilic compounds which form covalent adducts with TRPA1. Allyl isothiocyanate (AITC), the common reference agonist used to identify TRPA1, contains a reactive electrophilic group that covalently binds with cysteine residues of TRPA1 and confers a structural change on the channel...
June 15, 2017: Journal of Pharmacology and Experimental Therapeutics
https://www.readbyqxmd.com/read/28617611/palladium-catalyzed-arylation-and-benzylation-of-nitroarenes-using-aryl-sulfonates-and-benzyl-acetates
#20
Zubaoyi Yi, Yodit Aschenaki, Ryan Daley, Stephen Davick, Abigail Schnaith, Rylee Wander, Dipannita Kalyani
Pd-catalyzed arylation or benzylation of nitroazoles using aryl sulfonates or benzyl acetates is described. Electronically varied aryl tosylates and mesylates, as well as benzyl acetates, afford the arylated and benzylated products. Arylation of nitrobenzene is also reported. The relative rate for the arylation of halides is greater than that of tosylates using the reported reaction parameters. These studies enhance the scope of electrophiles for nitroarene arylations and benzylations, which was hitherto limited to the use of halide electrophiles...
June 15, 2017: Journal of Organic Chemistry
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