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https://www.readbyqxmd.com/read/29792332/ligation-enhanced-%C3%AF-hole%C3%A2-%C3%A2-%C3%A2-%C3%AF-interactions-involving-isocyanides-effect-of-%C3%AF-hole%C3%A2-%C3%A2-%C3%A2-%C3%AF-noncovalent-bonding-on-conformational-stabilization-of-acyclic-diaminocarbene-ligands
#1
Alexander S Mikherdov, Mikhail A Kinzhalov, Alexander S Novikov, Vadim P Boyarskiy, Irina A Boyarskaya, Margarita S Avdontceva, Vadim Yu Kukushkin
The reaction of cis-[PdCl2 (CNXyl)2 ] (Xyl = 2,6-Me2 C6 H3 ) with the aminoazoles [1 H-imidazol-2-amine (1), 4 H-1,2,4-triazol-3-amine (2), 1 H-tetrazol-5-amine (3), 1 H-benzimidazol-2-amine (4), 1-alkyl-1 H-benzimidazol-2-amines, where alkyl = Me (5), Et (6)] in a 2:1 ratio in the presence of a base in CHCl3 at RT proceeds regioselectively and leads to the binuclear diaminocarbene complexes [(ClPdCNXyl)2 {μ-C(N-azolyl)N(Xyl)C═NXyl}] (7-12; 73-91%). Compounds 7-12 were characterized by C, H, N elemental analyses, high-resolution ESI+ -MS, Fourier transform infrared spectroscopy, 1D (1 H, 13 C) and 2D (1 H,1 H-COSY, 1 H,1 H-NOESY, 1 H,13 C-HSQC, 1 H,13 C-HMBC) NMR spectroscopies, and X-ray diffraction (XRDn)...
May 24, 2018: Inorganic Chemistry
https://www.readbyqxmd.com/read/29791067/synergistic-catalysis-enabled-reaction-of-2-indolymethanols-with-oxonium-ylides-construction-of-3-indolyl-3-alkoxy-oxindole-framework
#2
Chun Ma, Jia-Yu Zhou, Yi-Zhu Zhang, Yin-Chun Jiao, Guang-Jian Mei, Feng Shi
A synergistic catalysis-enabled reaction of 2-indolymethanols with oxonium ylides has been established, which makes use of the three-component reaction of 3-diazooxindoles, alcohols and 2-indolymethanols under the cooperative catalysis of metal complex and Brønsted acid. This reaction has not only provided a new approach for constructing 3-indolyl-3-alkoxy oxindole scaffolds by utilizing the indole C3-electrophilicity, but also realized a nucleophilic addition of metal associated ylide to 2-indolylmethanols for the first time...
May 23, 2018: Chemistry, An Asian Journal
https://www.readbyqxmd.com/read/29790765/metal-template-assisted-proximal-arrangement-of-a-nucleophile-and-an-electrophile-site-selective-acylation-of-%C3%AE-hydroxyamides-in-polyols
#3
Yasuhiro Nishikawa, Kohei Takemoto, Kana Matsuda, Risa Tanaka, Akira Arashima, Kanako Ito, Yuki Kamezawa, Yuna Hori, Osamu Hara
Site-selective acylation of α-hydroxyl groups in amides has been achieved in the presence of other primary hydroxyl groups with intrinsic high reactivity. In this methodology, a relatively stable pyridine aldoxime ester was exploited as an acyl donor to suppress undesired acylation. The catalytic activation of a pyridine aldoxime ester with a Lewis acid produced a cationic complex, which preferentially attracted the Lewis basic α-hydroxyamide via a template effect, to thus facilitate o-acylation.
May 23, 2018: Organic Letters
https://www.readbyqxmd.com/read/29790759/cyclization-of-ketones-with-nitriles-under-base-a-general-and-economical-synthesis-of-pyrimidines
#4
Lebin Su, Kang Sun, Neng Pan, Long Liu, Mengli Sun, Jianyu Dong, Yongbo Zhou, Shuang-Feng Yin
A facile, general, and economical synthesis of diversely functionalized pyrimidines has been realized under basic conditions via the copper-catalyzed cyclization of ketones with nitriles. The reaction proceeds via a novel pathway involving the nitriles acting as electrophiles and consecutive C-C bond and two C-N bond formations and shows broad substrate scope and good tolerance of many important functional groups. This strategy represents a new platform for constructing pyrimidine structures.
May 23, 2018: Organic Letters
https://www.readbyqxmd.com/read/29790752/an-experiment-cum-computational-study-on-the-regioselectivity-of-nucleophilic-addition-to-unsymmetrical-p-benzynes-derived-from-bergman-cyclization-of-enediynes
#5
Eshani Das, Shyam Basak, Anakuthil Anoop, Amit Basak
The regioselectivity in addition of nucleophiles to the p-benzyne intermediates derived from unsymmetrical aza- substituted enediynes via Bergman Cyclization was studied. Computational studies [using UB3LYP/6-31G(d,p) level of theory] suggest that the p-benzyne intermediate retains its similar electrophilic character at the two radical centres even under unsymmetrical electronic perturbation, thus supporting the predicted model of nucleophilic addition to p- benzyne proposed by Perrin and O'Connor (JACS 2007) and later by Alabugin et al...
May 23, 2018: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29789842/synthesis-of-%C3%AE-cf-3-and-%C3%AE-cf-2-h-amines-via-the-aminofluorination-of-fluorinated-alkenes
#6
Ling Yang, Wen-Xin Fan, E Lin, Dong-Hang Tan, Qingjiang Li, Honggen Wang
A novel synthesis of α-CF3 and α-CF2H amines via the aminofluorination of gem-difluoroalkenes and mono-fluoroalkenes, respectively, is reported. The method employs Selectfluor as an electrophilic fluorine source and acetonitrile as a nitrogen source. Mechanistic studies revealed a single-electron oxidation/fluorine-abstraction/Ritter-type amination pathway. The protocol allowed the synthesis of a broad range of fluorinated amines including those bearing quaternary carbon centers with good efficiency and functional group tolerance...
May 23, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29786926/catalytic-thorpe-ingold-effect-for-branch-selective-alkylation-of-unactivated-aryl-fluorides
#7
Matthew J O'Neill, Tim Riesebeck, Josep Cornella
Herein, we present a general protocol for the alkylation of simple aryl fluorides with unbiased secondary Grignard reagents by means of Ni catalysis. This study revealed a general Thorpe-Ingold effect in the ligand backbone which confers a high degree of selectivity for the secondary position in the C-C coupling event. Such protocol is characterized by its mild conditions, robustness and simplicity. Both electron-rich and electron-deficient aryl fluorides are suitable candidates in this transformation. Equally amenable are a variety of heterocycles, permitting the coupling without over alkylation at the electrophilic sites...
May 22, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29785418/regioselective-ortho-functionalization-of-bromofluorenecarbaldehydes-using-tmpmgcl%C3%A2-licl
#8
Dominik Göbel, Nils Clamor, Boris J Nachtsheim
A highly regioselective functionalization of 7-bromofluorene-2-carbaldehydes, potent organic chromophores, in position C3 using a mild ortho-metallation strategy (DoM) with TMPMgCl·LiCl has been developed. This approach allows the preparation of highly functionalized fluorene derivatives by conversion of the in situ generated metalated species with various electrophiles giving a fast access to novel organic phosphorescent dyes.
May 22, 2018: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/29782144/the-nitro-group-as-a-masked-electrophile-in-covalent-enzyme-inhibition
#9
Sneha Ray, Dale F Kreitler, Andrew M Gulick, Andrew S Murkin
We report the unprecedented reaction between a nitroalkane and an active-site cysteine residue to yield a thiohydroximate adduct. Structural and kinetic evidence suggests the nitro group is activated by conversion to its nitronic acid tautomer within the active site. The nitro group, therefore, shows promise as a masked electrophile in the design of covalent inhibitors targeting binding pockets with appropriately placed cysteine and general acid residues.
May 21, 2018: ACS Chemical Biology
https://www.readbyqxmd.com/read/29781487/a-disguised-hydride-in-a-butylmagnesium-cation
#10
Sumanta Banerjee, Ankur, Alex Andrews, Ajay Venugopal
The ability of the β-CH functionality in a butylmagnesium cation [Me6TREN-Mg-n-Bu]+ to quantitatively reduce benzophenone has been demonstrated. The hydridic nature of the β-CH functionality is highlighted by its abstraction using B(C6F5)3. β-CH abstraction over alkylation in [Me6TREN-Mg-n-Bu]+ is dependent on the nature of the incoming electrophile and the polarity of the solvent.
May 21, 2018: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/29780566/nontrigonal-constraint-enhances-1-2-addition-reactivity-of-phosphazenes
#11
Yi-Chun Lin, James C Gilhula, Alexander T Radosevich
The syntheses and 1,2-addition reactivities of nontrigonal phosphazenes supported by trianionic tricoordinating chelates of the type L3 P 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 1111111111111111111111111111111111 1111111111111111111111111111111111 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 0000000000000000000000000000000000 Ndipp ( 3 : L3 = N[CHC( t Bu)O]2 3- ; 4 : L3 = N( o -NMeC6 H4 )2 3- ; dipp = 2,6-diisopropylphenyl) are reported...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29780564/an-iridium-iii-iv-v-redox-series-featuring-a-terminal-imido-complex-with-triplet-ground-state
#12
Markus Kinauer, Martin Diefenbach, Heiko Bamberger, Serhiy Demeshko, Edward J Reijerse, Christian Volkmann, Christian Würtele, Joris van Slageren, Bas de Bruin, Max C Holthausen, Sven Schneider
The iridium(iii/iv/v) imido redox series [Ir(N t Bu){N(CHCHP t Bu2 )2 }]0/+/2+ was synthesized and examined spectroscopically, magnetically, crystallographically and computationally. The monocationic iridium(iv) imide exhibits an electronic doublet ground state with considerable 'imidyl' character as a result of covalent Ir-N t Bu bonding. Reduction gives the neutral imide [Ir(N t Bu){N(CHCHP t Bu2 )2 }] as the first example of an iridium complex with a triplet ground state. Its reactivity with respect to nitrene transfer to selected electrophiles (CO2 ) and nucleophiles (PMe3 ), respectively, is reported...
May 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29779661/characterization-and-biochemical-assays-of-streptomyces-vanadium-dependent-chloroperoxidases
#13
Shaun M K McKinnie, Zachary D Miles, Bradley S Moore
Vanadium-dependent haloperoxidases (VHPOs) are fascinating enzymes that facilitate electrophilic halogen incorporation into electron-rich substrates, simply requiring vanadate, a halide source, and cosubstrate hydrogen peroxide for activity. Initially characterized in fungi and red algae, VHPOs were long believed to have limited regio-, chemo-, and enantioselectivity in the production of halogenated metabolites. However, the recent discovery of homologues in the biosynthetic gene clusters of the stereoselectively halogenated meroterpenoids from marine-derived Streptomyces bacteria has revised this paradigm...
2018: Methods in Enzymology
https://www.readbyqxmd.com/read/29779660/in-vitro-analysis-of-cyanobacterial-nonheme-iron-dependent-aliphatic-halogenases-welo5-and-ambo5
#14
Xinyu Liu
Aliphatic carbon-halogen (C-X) bonds are prevalent in modern pharmaceuticals and bioactive natural products. Three distinct chemical strategies are known in Nature to generate these structural motifs. The first is via the nucleophilic substitution at a prefunctionalized electrophilic carbon center with a halide anion (X- ), known for the S-adenosyl-l-methionine-dependent halogenases. The second is via the electrophilic activation of an alkene or its equivalent by a halenium ion (X+ ) donor, known for the haloperoxidases and flavin-dependent halogenases...
2018: Methods in Enzymology
https://www.readbyqxmd.com/read/29779193/functional-role-of-tyr12-in-the-catalytic-activity-of-novel-zeta-like-glutathione-s-transferase-from-acidovorax-sp-kks102
#15
Dayyabu Shehu, Zazali Alias
Glutathione S-transferases (GSTs) are a family of enzymes that function in the detoxification of variety of electrophilic substrates. In the present work, we report a novel zeta-like GST (designated as KKSG9) from the biphenyl/polychlorobiphenyl degrading organism Acidovorax sp. KKS102. KKSG9 possessed low sequence similarity but similar biochemical properties to zeta class GSTs. Functional analysis showed that the enzyme exhibits wider substrate specificity compared to most zeta class GSTs by reacting with 1-chloro-2,4-dinitrobenzene (CDNB), p-nitrobenzyl chloride (NBC), ethacrynic acid (EA), hydrogen peroxide, and cumene hydroperoxide...
May 19, 2018: Protein Journal
https://www.readbyqxmd.com/read/29778798/discovery-of-antitumor-ursolic-acid-long-chain-diamine-derivatives-as-potent-inhibitors-of-nf-%C3%AE%C2%BAb
#16
Wei Jiang, Ri-Zhen Huang, Jing Zhang, Tong Guo, Meng-Ting Zhang, Xiao-Chao Huang, Bin Zhang, Zhi-Xin Liao, Jing Sun, Heng-Shan Wang
A series of inhibitors of NF-κB based on ursolic acid (UA) derivatives containing long-chain diamine moieties were designed and synthesized as well as evaluated the antitumor effects. These compounds exhibited significant inhibitory activity to the NF-κB with IC50 values at micromolar concentrations in A549 lung cancer cell line. Among them, compound 8c exerted potent activity against the test tumor cell lines including multidrug resistant human cancer lines, with the IC50 values ranged from 5.22 to 8.95 μM...
May 8, 2018: Bioorganic Chemistry
https://www.readbyqxmd.com/read/29777359/regulatory-mechanisms-of-thiol-based-redox-sensors-lessons-learned-from-structural-studies-on-prokaryotic-redox-sensors
#17
REVIEW
Sang Jae Lee, Dong-Gyun Kim, Kyu-Yeon Lee, Ji Sung Koo, Bong-Jin Lee
Oxidative stresses, such as reactive oxygen species, reactive electrophilic species, reactive nitrogen species, and reactive chlorine species, can damage cellular components, leading to cellular malfunction and death. In response to oxidative stress, bacteria have evolved redox-responsive sensors that enable them to simultaneously monitor and eradicate potential oxidative stress. Specifically, redox-sensing transcription regulators react to oxidative stress by means of modifying the thiol groups of cysteine residues, functioning as part of an efficient survival mechanism for many bacteria...
May 17, 2018: Archives of Pharmacal Research
https://www.readbyqxmd.com/read/29775963/brain-ischemic-preconditioning-protects-against-ischemic-injury-and-preserves-the-blood-brain-barrier-via-oxidative-signaling-and-nrf2-activation
#18
Tuo Yang, Yang Sun, Leilei Mao, Meijuan Zhang, Qianqian Li, Lili Zhang, Yejie Shi, Rehana K Leak, Jun Chen, Feng Zhang
Brain ischemic preconditioning (IPC) with mild ischemic episodes is well known to protect the brain against subsequent ischemic challenges. However, the underlying mechanisms are poorly understood. Here we demonstrate the critical role of the master redox transcription factor, nuclear factor (erythroid-derived 2)-like 2 (Nrf2), in IPC-mediated neuroprotection and blood-brain barrier (BBB) preservation. We report that IPC causes generation of endogenous lipid electrophiles, including 4-hydroxy-2-nonenal (4-HNE), which release Nrf2 from inhibition by Keap1 (via Keap1-C288) and inhibition by glycogen synthase kinase 3β (via GSK3β-C199)...
May 6, 2018: Redox Biology
https://www.readbyqxmd.com/read/29775319/operando-evidence-for-a-universal-oxygen-evolution-mechanism-on-thermal-and-electrochemical-iridium-oxides
#19
Viktoriia A Saveleva, Li Wang, Detre Teschner, Travis E Jones, Aldo S Gago, K Andreas Friedrich, Spyridon Zafeiratos, Robert Schloegl, Elena R Savinova
Progress in the development of the proton exchange membrane (PEM) water electrolysis technology requires decreasing the anode overpotential, where the sluggish multistep oxygen evolution reaction (OER) occurs. This calls for the understanding of the nature of the active OER sites and reaction intermediates, which are still being debated. In this work, we apply synchrotron radiation - based near ambient pressure X-ray photoelectron and absorption spectroscopies under operando conditions in order to unveil the nature of the reaction intermediates and shed light on the OER mechanism on electrocatalysts most widely used in PEM electrolyzers - electrochemical and thermal iridium oxides...
May 18, 2018: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/29775301/enantioselective-synthesis-of-anti-1-2-diamines-by-cu-catalyzed-reductive-couplings-of-azadienes-with-aldimines-and-ketimines
#20
Xinxin Shao, Kangnan Li, Steven J Malcolmson
Here we report highly efficient and chemoselective azadiene-imine reductive couplings catalyzed by (Ph-BPE)Cu-H that afford anti-1,2-diamines. In all cases, reactions take place with either aldimine or ketimine electrophiles to deliver a single diastereomer of product in >95:5 er. The products' diamines are easily differentiable, facilitating down-stream synthesis.
May 18, 2018: Journal of the American Chemical Society
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