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Raul Garcia-Rodriguez, Álvaro Álvaro García-Romero, Alex J Plajer, Lucia Álvarez-Miguel, Andrew Bond, Dominic S Wright
Post-functionalisation of the aluminate anion [EtAl(6-Me-2-py)3]- (1) (2-py = 2-pyridyl) with alkoxide ligands can be achieved by the selective reactions of the lithium salt 1Li with alcohols in the appropriate stoichiometry. This method can be used to introduce 3-py and 4-py functionality, while maintaining the integrity of the aluminate framework, thereby giving entry to new supramolecular chemistry. Chirality can be introduced either by using a chiral alcohol as a reactant or by the step-wise reaction of 1Li with two different non-chiral alcohols...
August 9, 2018: Chemistry: a European Journal
Craig Johnston, Thomas West, Ruth Dooley, Marc Reid, Ariana B Jones, Edward King, Andrew G Leach, Guy C Lloyd-Jones
The mechanism of CF3 transfer from R3SiCF3 (R = Me, Et, iPr) to ketones and aldehydes, initiated by M+X- (<0.004 to 10 mol%) has been investigated by analysis of kinetics (variable-ratio stopped-flow NMR and IR), 13C/2H KIEs, LFER, addition of ligands (18-c-6, crypt-222), and density functional theory (DFT) calculations. The kinetics, reaction orders, and selectivity vary substantially with reagent (R3SiCF3) and initiator (M+X-). Traces of exogenous inhibitors present in the R3SiCF3 reagents, which vary substantially in proportion and identity be-tween batches and suppliers, also affect the kinetics...
August 6, 2018: Journal of the American Chemical Society
J Perego, D Piga, S Bracco, P Sozzani, A Comotti
The synthesis of porous organic 3D frameworks, wherein amine, hydroxyl and Li-alkoxide functions were built directly on the monomer-unit carbon core, realizes improved interactions with target gases. CO2 was retained by the amine group with a remarkable energy of 54 kJ mol-1, while 2D MAS NMR provided rare evidence of amine-to-gas short-distance interactions. Frameworks containing hydroxyl and Li-alkoxide functions show optimal interaction energies with CH4 of up to 25 kJ mol-1. The light network of 3-branch building units ensures the expandability of the nano-sponges...
August 3, 2018: Chemical Communications: Chem Comm
Yuan-Peng Du, Florent Héroguel, Jeremy S Luterbacher
Catalyst overcoating is an emerging approach to engineer surface functionalities on supported metal catalyst and improve catalyst selectivity and durability. Alumina deposition on high surface area material by sol-gel chemistry is traditionally difficult to control due to the fast hydrolysis kinetics of aluminum-alkoxide precursors. Here, sol-gel chemistry methods are adapted to slow down these kinetics and deposit nanometer-scale alumina overcoats. The alumina overcoats are comparable in conformality and thickness control to overcoats prepared by atomic layer deposition even on high surface area substrates...
July 25, 2018: Small
Shiva Moaven, Jingze Yu, Maythe Vega, Daniel K Unruh, Anthony F Cozzolino
Artificial vesicles can aid in the study and understanding of biological cell membranes. This study employs pnictogen bonding to actively direct the self-assembly of a true reversed bilayer. Antimony(iii) alkoxide cages that self-assemble through multiple strong SbO interactions propagate in two dimensions to form a reverse bilayer structure in the solid state. Long alkyl tails allow these reverse bilayers to be processed into vesicles in solution that are a reverse of biological cell membranes.
August 7, 2018: Chemical Communications: Chem Comm
Jonas Schaab, Miriam Schwab, Daniel Kratzert, Jan Schwabedissen, Hans-Georg Stammler, Norbert W Mitzel, Ingo Krossing
The thermally unstable α-fluoroalcohol undecafluorocyclohexanol (c-C6F11OH) was prepared by addition of hydrogen fluoride to the corresponding ketone. c-C6F10(CF3)OH was obtained by protonation of its alkoxide [NMe4]+[C7F13O]-. Decafluorocyclohexane-1,1-diol (c-C6F10(OH)2) was prepared by acidic workup of the corresponding alkoxide [NMe4]+[C6F11O]- with sulfuric acid, which yielded (c-C6F10(OH)2) and fluorosulfonic acid. The structures of c-C6F10(CF3)OH·2H2O and of (c-C6F10(OH)2) were elucidated by single-crystal X-ray and gas-phase electron-diffraction studies...
July 23, 2018: Chemical Communications: Chem Comm
Denis A Kuznetsov, Dmitry Konev, Sergey Sokolov, Ivan Fedyanin
Utilization of the metal alkoxides as the single-source precursors for the (mixed-)oxide materials offers remarkable benefits such as possibility to precisely control the metal ratio in the resulting material, highly homogeneous distribution of the elements in the film and low temperatures required for films processing. Here we report on the isolation and characterization of the bimetallic Co-Mo alkoxide, [Co3Mo4O10(OCH3)10(dmf)4] (Co3Mo4) (dmf = N,N-dimethylformamide), which was prepared through the anion metathesis reaction from the corresponding metal chlorides...
July 21, 2018: Chemistry: a European Journal
Michael Groll, Henry Nguyen, Sreekumar Vellalath, Daniel Romo
Upon acylation of the proteasome by the β-lactone inhibitor salinosporamide A (SalA), tetrahydrofuran formation occurs by intramolecular alkylation of the incipient alkoxide onto the choroethyl sidechain and irreversibly blocks the active site. Our previously described synthetic approach to SalA, utilizing a bioinspired, late-stage, aldol-β-lactonization strategy to construct the bicyclic β-lactone core, enabled synthesis of (⁻)-homosalinosporamide A (homoSalA). This homolog was targeted to determine whether an intramolecular tetrahydropyran is formed in a similar manner to SalA...
July 19, 2018: Marine Drugs
Aladdin M Srour, Siva S Panda, Asmaa M M Salman, May A El-Manawaty, Riham F George, ElSayed M Shalaby, Andrew N Fitch, Nehmedo G Fawzy, Adel S Girgis
AIM: Synthesis of novel bronchodilatory active indole-pyridine conjugates. Results/methodology: Indole-pyridine conjugates (6a-n, 8a-i and 10a-c) were synthesized in a facile pathway through reaction of 2-[(1-alkyl-1H-indol-3-yl)methylene]malononitriles 4a,b with the corresponding ketone-containing compounds (5a-f, 7a-c and 9a,b) in the presence of sodium alkoxide. Single (6l, 8 g) and powder (6k, 8d) x-ray studies supported the structures. RESULTS: Histamine precontracted isolated tracheal rings of guinea pig exhibited the potent bronchodilation properties of 6c (about double-fold potency relative to the standard reference, theophylline)...
July 18, 2018: Future Medicinal Chemistry
Maryam Yousif, Duleeka Wannipurage, Caleb D Huizenga, Elizabeth Washnock-Schmid, Nicholas J Peraino, Andrew Ozarowski, Sebastian A Stoian, Richard L Lord, Stanislav Groysman
The reaction of HOR' (OR' = di-t-butyl-(3,5-diphenylphenyl)methoxide) with an iron(II) amide precursor forms the iron(II) bis(alkoxide) complex Fe(OR')2 (THF)2 (2). 2 (5-10 mol %) serves as a catalyst for the conversion of aryl azides into the corresponding azoarenes. The highest yields are observed for aryl azides featuring two ortho substituents; other substitution patterns in the aryl azide precursor lead to moderate or low yields. The reaction of 2 with stoichiometric amounts (2 equiv) of the corresponding aryl azide shows the formation of azoarenes as the only organic products for the bulkier aryl azides (Ar = mesityl, 2,6-diethylphenyl)...
August 6, 2018: Inorganic Chemistry
Pargol Daneshmand, Leena Pinon, Frank Schaper
Dinuclear bis(R'-(R''-iminomethyl)phenoxide) copper complexes L2Cu2(μ-OR)2 were prepared from the reaction of copper methoxide with ROH and LH (ROH = dimethylaminoethanol or pyridylmethanol, R' = H, 4,6-tBu, 1,3-Cl, R'' = benzyl, cyclohexyl, diphenylmethyl and 2,6-dimethylphenyl). Preparation was complicated by formation of homoleptic L2Cu and only 9 of the 24 possible combinations could be prepared. All complexes were characterized by single crystal X-ray diffraction studies and crystallized as dinuclear penta-coordinated complexes...
July 31, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Weilong Xie, Sung-Woo Park, Hoimin Jung, Dongwook Kim, Mu-Hyun Baik, Sukbok Chang
Conjugate addition of organometallic reagents to α,β-unsaturated carbonyls is a key strategy for the construction of carbon-carbon bond in organic synthesis. Although direct C-H addition to unsaturated bonds via transition metal catalysis is explored in recent years, electron-deficient arenes that do not bear directing groups continue to be challenging. Herein we disclose the first example of a conjugate addition of perfluoroarenes to α,β-unsaturated carbonyls enabled by an alkoxide-hydrosilane system. The reaction is convenient to carry out at room temperature over a broad range of substrates and reactants to furnish synthetically versatile products in high to excellent yields...
August 1, 2018: Journal of the American Chemical Society
Timothy J Boyle, Jeremiah M Sears, Diana Perales, Roger E Cramer, Ping Lu, Rana O Chan, Bernadette A Hernandez-Sanchez
In an effort to generate single-source precursors for the production of metal-siloxide (MSiO x ) materials, the tris(trimethylsilyl)silanol (H-SST or H-OSi(SiMe3 )3 (1) ligand was reacted with a series of group 4 and 5 metal alkoxides. The group 4 products were crystallographically characterized as [Ti(SST)2 (OR)2 ] (OR = OPr i (2), OBu t (3), ONep (4)); [Ti(SST)3 (OBu n )] (5); [Zr(SST)2 (OBu t )2 (py)] (6); [Zr(SST)3 (OR)] (OR = OBu t (7), ONep, (8)); [Hf(SST)2 (OBu t )2 ] (9); and [Hf(SST)2 (ONep)2 (py) n ] ( n = 1 (10), n = 2 (10a)) where OPr i = OCH(CH3 )2 , OBu t = OC(CH3 )3 , OBu n = O(CH2 )3 CH3 , ONep = OCH2 C(CH3 )3 , py = pyridine...
July 6, 2018: Inorganic Chemistry
Matthias Van Zele, Jonathan Watté, Jan Hasselmeyer, Hannes Rijckaert, Yannick Vercammen, Steven Verstuyft, Davy Deduytsche, Damien P Debecker, Claude Poleunis, Isabel Van Driessche, Klaartje De Buysser
The thickness characterization of transparent protective coatings on functional, transparent materials is often problematic. In this paper, a toolbox to determine the thicknesses of a transparent coating on functional window films is presented. The toolbox consists of a combination of secondary ion mass spectrometry and profilometry and can be transferred to other transparent polymeric materials. A coating was deposited on designed model samples, which were characterized with cross-sectional views in transmission and in scanning/transmission electron microscopy and ellipsometry...
June 28, 2018: Materials
James Beament, Gabriele Kociok-Köhn, Matthew D Jones, Antoine Buchard
Four dimeric lanthanide alkoxide complexes bearing ONNO bipyrrolidine salan ligands (LMeH2/LtBuH2) have been prepared with Nd, Sm and Yb. Depending on the metal and substituents, these complexes adopt varying coordination geometries. While investigating the hydrolytic degradation of these complexes, three dimeric mixed alkoxide/hydroxide and bis-hydroxide products were also prepared, isolated and characterised. Despite paramagnetism, 1H NMR and diffusion ordered spectroscopy (DOSY) allowed additional characterisation alongside elemental and single-crystal X-ray diffraction analyses...
July 10, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Brittney E Petel, William W Brennessel, Ellen M Matson
We report the first example of oxygen-atom vacancy formation at the surface of a polyoxometalate, highlighting the ability of a polyoxovanadate-alkoxide cluster, [V6 O7 (OCH3 )12 ]1- , to function as a homogeneous model for reducible metal oxides. The removal of an oxide ion from [V6 O7 (OCH3 )12 ]1- results in the formation of a reactive vanadium(III) cation within the multimetallic framework. Generation of [V6 O6 (OCH3 )12 ]1- is confirmed by 1 H NMR, infrared and electronic absorption spectroscopies, as well as electrospray ionization mass spectrometry...
July 11, 2018: Journal of the American Chemical Society
Vladislav Vasilenko, Clemens K Blasius, Lutz H Gade
A comprehensive experimental and computational mechanistic study of the highly enantioselective hydroboration of ketones catalyzed by a manganese(II) alkyl boxmi pincer complex is reported. The catalyst operates at low catalyst loadings (down to 0.01 mol %) under very mild conditions (typically -40 °C) and facilitates the reduction of both aryl alkyl and dialkyl ketones with excellent selectivity (up to >95%ee). Catalyst activation pathways were investigated, demonstrating that a manganese(II) hydride and a manganese(II) alkoxide species are part of the catalytic cycle and can be generated via σ-bond metathesis of the alkyl precursor with the borane or by alcoholysis...
July 25, 2018: Journal of the American Chemical Society
Xingliang Li, Zhicheng Zhang, Leigh R Martin, Shunzhong Luo, Linfeng Rao
N-(2-Hydroxyethyl)ethylenediamine- N, N', N'-triacetic acid (HEDTA, denoted as H3 L in this work, and the three dissociable protons represent those of the three carboxylic groups) is a strong chelating ligand and plays an important role in the treatment and disposal of nuclear wastes as well as separation sciences of f-elements. In this work, the complexation of HEDTA with U(VI) was studied thermodynamically and structurally in aqueous solutions. Potentiometry and microcalorimetry were used to measure the complexation constants (298-343 K) and enthalpies (298 K), respectively, at I = 1...
July 2, 2018: Inorganic Chemistry
Katsuhiko Shimizu, Daniel E Morse
Silicatein, a silica-synthesizing, catalytic triad hydrolase, was discovered in the silica spicules comprising the skeletons of certain marine sponges. Sequence similarity is closest to that of the mammalian cathepsin L, a catalytic triad hydrolase and protease. Genetic substitutions of residues in the catalytic triad, the predictive activities of polymeric and small-molecule analogs of the enzyme, and the wide range of structures accepted as substrates all support a reaction mechanism closely analogous to that established for the classical catalytic triad hydrolases...
2018: Methods in Enzymology
Roberto Fallica, Benjamin Watts, Benedikt Rösner, Gioia Della Giustina, Laura Brigo, Giovanna Brusatin, Yasin Ekinci
We report on the near edge x-ray absorption fine structure (NEXAFS) spectroscopy of hybrid organic-inorganic resists. These materials are nonchemically amplified systems based on Si, Zr, and Ti oxides, synthesized from organically modified precursors and transition metal alkoxides by a sol-gel route and designed for ultraviolet, extreme ultraviolet (EUV) and electron beam lithography. The experiments were conducted using a scanning transmission x-ray microscope (STXM) which combines high spatial-resolution microscopy and NEXAFS spectroscopy...
September 7, 2018: Nanotechnology
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