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c-h bond activation

Rena Simayi, Simone M Gillbard, Warren B Cross, Eric G Hope, Kuldip Singh, Gregory A Solan
The pyridylimine-substituted 1-naphthalenes, 2-(1-C10H7)-6-{CR[double bond, length as m-dash]N(2,6-i-Pr2C6H3)}C5H3N (R = Me HLMe, H HLH), react with Na2[PdCl4] in acetic acid at elevated temperature to afford either ortho-C-Hnaphthyl activated (LMe)PdCl (2ortho) or the unactivated adduct (HLH)PdCl2 (1b). Alternatively, 1b and its ketimine analogue (HLMe)PdCl2 (1a), can be prepared by treating (MeCN)2PdCl2 with either HLMe or HLH in chloroform at room temperature. Regio-selective ortho-C-H activation to form 2ortho can also be initiated by the thermolysis of 1a in acetic acid, while no reaction occurs under similar conditions with 1b...
August 13, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Danuta Branowska, Justyna Ławecka, Mariusz Sobiczewski, Zbigniew Karczmarzyk, Waldemar Wysocki, Ewa Wolińska, Ewa Olender, Barbara Mirosław, Alicja Perzyna, Anna Bielawska, Krzysztof Bielawski
A new series of 1,2,4-triazine unsymmetrical disulfanes were prepared and evaluated as anticancer activity compounds against MCF-7 human breast cancer cells with some of them acting as low micromolar inhibitors. Evaluation of the cytotoxicity using an MTT assay, the inhibition of [3 H]-thymidine incorporation into DNA demonstrated that these products exhibit cytotoxic effects on breast cancer cells in vitro. The most effective compounds with 59 and 60 µM compared to chlorambucil with 47 µM were disulfanes bearing methyl and methoxy substituent in an aromatic ring...
2018: Monatshefte Für Chemie
Jia Ke, Qi Lu, Xin Wang, Rui Sun, Zhe Jin, Xiaoyi Zhan, Jianshu Hu, David Chi-Cheong Wan, Chun Hu
The epidermal growth factor receptors (EGFRs), in which overexpression (known as upregulation) or overactivity have been associated with a number of cancers, has become an attractive molecular target for the treatment of selective cancers. We report here the design and synthesis of a novel series of 4,5-dihydro-1 H -thieno [2',3':2,3]thiepino[4,5-c]pyrazole-3-carboxamide derivatives and the screening for their inhibitory activity on the EGFR high-expressing human A549 cell line using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)...
August 8, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
Ruud Ubink, Eef Hc Dirksen, Myrthe Rouwette, Ebo Sijbren Bos, Ingrid Janssen, David F Egging, Eline M Loosveld, Tanja A van Achterberg, Kim Berentsen, Miranda M C van der Lee, Francis Bichat, Olivier Raguin, Monique A J van der Vleuten, Patrick G Groothuis, Wim H A Dokter
Carboxylesterase 1c (CES1c) is responsible for linker-drug instability and poor pharmacokinetics (PK) of several antibody-drug conjugates (ADCs) in mouse, but not in monkey or human. Preclinical development of these ADCs could be improved if the PK in mice would more closely resemble that of human and is not affected by an enzyme that is irrelevant for humans. SYD985, a HER2-targeting ADC based on trastuzumab and linker-drug vc-seco-DUBA is also sensitive to CES1c. In the present studies, we first focused on the interaction between CES1c and SYD985 by size- exclusion chromatography, Western blotting and LC-MS/MS analysis, using recombinant CES1c and plasma samples...
August 9, 2018: Molecular Cancer Therapeutics
Xuecheng Li, Guanlun Guo, Ning Qin, Zhao Deng, Zhouguang Lu, Dong Shen, Xu Zhao, Yu Li, Bao-Lian Su, Hong-En Wang
Despite their high-energy density, low cost and environmental friendliness, the commercial application of lithium-sulfur batteries (LSBs) has been plagued by their severe capacity decay during long-term cycling caused by polysulfide shuttling. Herein, we demonstrate a synergetic vacancy and heterostructure engineering strategy using a nitrogen-doped graphene/SnS2/TiO2 (denoted as NG/SnS2/TiO2) nanocomposite to enhance the electrochemical performance of LSBs. It is noted that plentiful sulfur vacancy (Vs) defects and nanosized heterojunctions are created on the NG/SnS2/TiO2 composite as proved using electron paramagnetic resonance, transmission electron microscopy and X-ray photoelectron spectroscopy, which can serve as strong adsorption and activation sites for polar polysulfide intermediates, prevent their dissolution/shuttling, and accelerate their redox reaction...
August 9, 2018: Nanoscale
Jens Blotevogel, Anthony K Rappe, Arthur N Mayeno, Tom Sale, Thomas Borch
The permanganate ion (MnO4-) has been widely used as reagent for water treatment for over a century. It is a strong enough oxidant to activate carbon-hydrogen bonds, one of the most important reactions in biological and chemical systems. Our current textbook understanding of the oxidation mechanism in aqueous solution involves an initial, rate-limiting hydride abstraction by permanganate followed by reaction of the carbocation with bulk water to form an alcohol. This mechanism fits well into the classic oxidation sequence of alkane → alcohol → aldehyde → carboxylate, the central paradigm for both abiotic and biotic alkane oxidation in aqueous environments...
August 8, 2018: Environmental Science & Technology
Josiane V Cruz, Rodolfo B Serafim, Gabriel M da Silva, Silvana Giuliatti, Joaquín M C Rosa, Moysés F Araújo Neto, Franco H A Leite, Carlton A Taft, Carlos H T P da Silva, Cleydson B R Santos
Receptor-interacting protein kinase 2 (RIPK2) plays an essential role in autoimmune response and is suggested as a target for inflammatory diseases. A pharmacophore model was built from a dataset with ponatinib (template) and 18 RIPK2 inhibitors selected from BindingDB database. The pharmacophore model validation was performed by multiple linear regression (MLR). The statistical quality of the model was evaluated by the correlation coefficient (R), squared correlation coefficient (R2 ), explanatory variance (adjusted R2 ), standard error of estimate (SEE), and variance ratio (F)...
August 7, 2018: Journal of Molecular Modeling
Hsueh-Ju Liu, Micah S Ziegler, T Don Tilley
An unusual cyclometalation reaction results from a C-C bond activation in Cp*(IPr)RuCl to give Cp*(IPr')Ru(L) featuring a NHC-C(sp2) chelating ligand (5-L; L = propene, N2; IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene; IPr' = 1-(6-isopropylphenyl)-3-(2,6-diisopropylphenyl)imidazol-2-ylidene). DFT calculations were employed to elucidate the C-C bond activation pathway. Reactions of cyclometalated ruthenium complexes bearing NHC-C(sp2) and NHC-C(sp3) ligands (5-L and Cp*(IXy-H)Ru(N2), 1a, respectively where IXy = 1,3-bis(2,6-dimethylphenyl)-imidazol-2-ylidene; IXy-H is the deprotonated form of (IXy)) are reported...
August 7, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Nuttapon Yodsin, Chompoonut Rungnim, Vinich Promarak, Supawadee Namuangruk, Nawee Kungwan, Rattanawalee Rattanawan, Siriporn Jungsuttiwong
We used density functional theory (DFT) to investigate hydrogen adsorption and diffusion on platinum-decorated carbon nanocones (Pt-CNCs). The curvature presented in the conical section of CNC materials affects the Pt binding stability. The role of Pt atoms as an active catalyst for H2 adsorption and dissociation has been investigated in perfect Pt-4CNC and defect Pt-v4CNC systems. Then, the spillover mechanism of dissociated hydrogen atoms in Pt-v4CNC is explored via two reaction steps: (i) H-migration from Pt to carbon atoms and (ii) H-diffusion via the C-C route throughout the CNC surface...
August 7, 2018: Physical Chemistry Chemical Physics: PCCP
Kuangbiao Liao, Yun-Fang Yang, Yingzi Li, Jacob N Sanders, K N Houk, Djamaladdin G Musaev, Huw M L Davies
C-H functionalization represents a promising approach for the synthesis of complex molecules. Instead of relying on modifying the functional groups present in a molecule, the synthetic sequence is achieved by carrying out selective reactions on the C-H bonds, which traditionally would have been considered to be the unreactive components of a molecule. A major challenge is to design catalysts to control both the site- and stereoselectivity of the C-H functionalization. We have been developing dirhodium catalysts with different selectivity profiles in C-H functionalization reactions with donor/acceptor carbenes as reactive intermediates...
August 6, 2018: Nature Chemistry
Qing Li, Jianzhi Gao, Youyong Li, Miguel Fuentes-Cabrera, Mengxi Liu, Xiaohui Qiu, Haiping Lin, Lifeng Chi, Minghu Pan
The synthetic challenges of radialenes have precluded their practical applications. Here, we report a one-step synthetic protocol of [4]radialene on a copper surface. High-resolution scanning tunneling microscopy measurements reveal that such catalytic reaction proceeds readily with high selectivity at the temperature below 120 K. First-principles calculations show that the reaction pathway is characterized by firstly the cooperative inter-molecular hydrogen tautomerization and then the C-C bond formation...
August 6, 2018: Nature Communications
Ismail Warad, Firas F Awwadi, Bahaa Abd Al-Ghani, Ashraf Sawafta, Naveen Shivalingegowda, Neartur Krishnappagowda Lokanath, Mohammad S Mubarak, Taibi Ben Hadda, Abdelkader Zarrouk, Fuad Al-Rimawi, Abdallah Bani Odeh, Sameer A Barghouthi
Two new hydrated monocationic Cu(II) complexes with 1,3-propylenediamine and 1,2-ethylenediamine of general formula [CuBr(N-N)2 ·H2 O]Br were prepared. The complexes were identified by means of several spectroscopic tools (Uv-visible, IR and MS), thermally (TG/DTA) and CHN-elemental analysis. The three dimensional structure for complex A and B was provide by X-ray diffraction studies and showed the Cu(II) ion as 4 + 1 + 1 coordinated, four nitrogen atoms of the diamine ligands, one bromide ion and one H2 O semi-coordinated to the Cu(II) center, a typical trans effect is clearly observed in the two complexes...
November 2018: Ultrasonics Sonochemistry
Yong Xia, Lin Wang, Armido Studer
A general and practical strategy for remote site-selective functionalization of unactivated aliphatic C-H bonds in various amides via radical chemistry is introduced. C-H bond functionalization is achieved by using the readily installed N-allylsulfonyl moiety as a N-radical precursor. The in situ generated N-radical engages in intramolecular 1,5-hydrogen atom transfer to generate a translocated C-radical which is subsequently trapped with various sulfone reagents to afford the corresponding C-H functionalized amides...
August 6, 2018: Angewandte Chemie
Ryo Yamamoto, Shoma Minami, Tsunehisa Okuno
The title compound, C19 H14 N2 O4 , was found to have two crystal polymorphs, in which the molecular structures of the diacetylenic compound are broadly similar. The main structural difference between the polymorphs concerns the intermolecular hydrogen-bonding motifs adopted, namely a one-dimensional zigzag polymer linked by N-H...N(py) (py is pyridine) interactions in polymorph I and a centrosymmetric dimeric motif formed by N-H...O=C interactions in polymorph II. The diacetylene cores of the molecules stack along the a and b axes in polymorphs I and II, respectively...
August 1, 2018: Acta Crystallographica. Section C, Structural Chemistry
Michela Milan, Michela Salamone, Miquel Costas, Massimo Bietti
Aliphatic C-H bond functionalization is at the frontline of research because it can provide straightforward access to simplified and cost-effective synthetic procedures. A number of these methodologies are based on hydrogen atom transfer (HAT), which, as a consequence of the inert character of C-H bonds, often represents the most challenging step of the overall process. Because the majority of organic molecules contain multiple nonequivalent C-H bonds that display similar chemical properties, differentiating between these bonds with high levels of selectivity represents one of the most challenging issues...
August 6, 2018: Accounts of Chemical Research
Masahiro Shimizu, Jun Kikuchi, Azusa Kondoh, Masahiro Terada
An enantioselective intramolecular anti -SN 2' cyclization reaction for the construction of a quaternary stereogenic center was accomplished through the activation of the leaving group using a binaphthol-derived phosphoramide as the chiral Brønsted acid catalyst. The present allylic substitution reaction is beneficial not only for the regioselective nucleophilic substitution at the multi-substituted site of the double bond but also for controlling the stereochemical outcome because of using a geometrically defined double bond...
July 14, 2018: Chemical Science
Atsuhiro Shimada, Keita Hatano, Hitomi Tadehara, Naomine Yano, Kyoko Shinzawa-Itoh, Eiki Yamashita, Kazumasa Muramoto, Tomitake Tsukihara, Shinya Yoshikawa
Cytochrome c oxidase (CcO) is the terminal oxidase of cellular respiration, reducing O2 to water and pumping protons. X-ray structural features have suggested that CcO pumps protons via a mechanism involving electrostatic repulsions between pumping protons in the hydrogen bond network of a proton-conducting pathway (the H-pathway) and net positive charges created upon oxidation of an iron site, heme α (Fe α 2+ ), for reduction of O2 at another iron site, heme α3 (Fe α3 2+ ). The protons for pumping are transferred to the hydrogen bond network from the N-side via the water channel of the H-pathway...
August 3, 2018: Journal of Biological Chemistry
T V Ajay Kumar, Alias Anand S Athavan, C Loganathan, K Saravanan, S Kabilan, V Parthasathy
Transforming growth factor-β (TGF-β) family members plays a vital role in regulating hormonal function, bone formation, tissue remodeling, and erythropoiesis, cell growth and apoptosis. TGF-β super-family members mediate signal transduction via serine/threonine kinase receptors located on the cell membrane. Variation in expression of the TGF-β type I and II receptors in the cancer cells compromise its tumor suppressor activities which direct to oncogenic functions. The present study was aimed to screen the potent TGF-β type I inhibitors through atom based 3D-QSAR and pharmacophore modelling...
July 24, 2018: Computational Biology and Chemistry
Daniel H Scharf, Jan D Dworschak, Pranatchareeya Chankhamjon, Kirstin Scherlach, Thorsten Heinekamp, Axel A Brakhage, Christian Hertweck
Gliotoxin is a virulence factor of the human pathogen Aspergillus fumigatus, the leading cause of invasive aspergillosis. The activity of this metabolite is mediated by a transannular disulfide bond, a hallmark of the epipolythiodiketopiperazine (ETP) family. Through the creation of fungal gene deletion mutants, metabolic profiling and heterologous protein expression, we unveiled the critical role of the cytochrome P450 monooxygenase (CYP450) GliC for the stepwise bishydroxylation of the diketopiperazine (DKP) core...
August 3, 2018: ACS Chemical Biology
Maral Gholamhosseyni, Ebrahim Kianmehr
Ruthenium catalyzed oxidative alkenylation of N-aryl pyridazinediones and N-aryl phthalazinediones with acrylates and subsequent intramolecular cyclization of the resulting product in water as a green solvent were accomplished. Diverse derivatives of pyridazino[1,2-a]indazoles and indazolo[1,2-b]phthalazines were readily prepared in moderate to high yields by this methodology from easily accessible starting materials via cascade directed C-H bond activation/annulation reactions.
August 3, 2018: Organic & Biomolecular Chemistry
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