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Tomasz Pietrzak, Iwona Justyniak, Jiwon Victoria Park, Michał Terlecki, Łukasz Kapuśniak, Janusz Lewinski
Despite decades of extensive studies on the reactivity of magnesium alkyls towards O₂, the isolation and structural characterization of discrete products of these reactions still remains a challenge. Although the formation of the most frequently encountered magnesium alkoxides via unstable alkylperoxide intermediates has commonly been accepted, the latter species have been elusive for over 100 years. Probing the oxygenation of a well-defined neo-pentylmagnesium complex stabilized by a β-diketminate ligand, (dippBDI)MgCH₂CMe₃, we report on the isolation and structure characterization of both a dimeric magnesium alkoxide [(dippBDI)Mg(µ-OCH₂CMe₃)]2 and the first example of monomeric magnesium alkylperoxide [(dippBDI)Mg(thf)OOCH₂CMe₃] (dippBDI = [(ArNCMe)₂CH]- and Ar = C₆H₃iPr₂-2,6)...
December 5, 2018: Chemistry: a European Journal
Ze Kan, Wenlong Luo, Tong Shi, Chuanzhi Wei, Binghao Han, Dejuan Zheng, Shaofeng Liu
Ring-opening polymerization (ROP) of cyclic esters/lactones by efficient catalysts is a powerful method for synthesis of biodegradable and biocompatible polyesters with well-defined structures. To develop catalytic systems that are fast, selective and controlled is a persistent effort of chemists. In this contribution, we report a binary urea/alkoxide catalytic system that could catalyze ROP of rac -LA in a fast (over 90% conversion within 1-2 min), stereoselective ( P i up to 0.93) and controlled manner, indicated by narrow MW distributions, linear relationship between the monomer conversions and M n s, end-group fidelity, and chain extension experiments...
2018: Frontiers in Chemistry
Alexandre Amormino S Gonçalves, Mietek Jaroniec
The one-pot synthesis of nanostructured ternary mixed oxides is challenging due to the heterogeneous nature of the hydrolysis and condensation processes of all metal oxide precursors. In addition, the solvents and additives used can affect these processes too. Herein, we report the effect of different solvents (ethanol, 1- and 2-propanol, or butanol) and additives (citric acid or 1,3,5-triisopropylbenzene) used on the formation of binary and ternary alumina-based oxides, NiO-Al2 O3 , NiO-TiO2 -Al2 O3 , and NiO-ZrO2 -Al2 O3 in the presence of triblock copolymer Pluronic P123 used as a soft template...
November 14, 2018: Journal of Colloid and Interface Science
Rafael O Costa, Sarah S Ferreira, Crystiane A Pereira, Jeffrey R Harmer, Christopher J Noble, Gerhard Schenk, Roberto W A Franco, Jackson A L C Resende, Peter Comba, Asha E Roberts, Christiane Fernandes, Adolfo Horn
The synthesis, X-ray molecular structure, physico-chemical characterization and dual antioxidant activity (catalase and superoxide dismutase) of a new polymeric mixed valence Mn(III)Mn(II) complex, containing the ligand H2 BPClNOL (N-(2-hydroxybenzyl)-N-(2-pyridylmethyl)[(3-chloro)(2-hydroxy)] propylamine) is described. The monomeric unit is composed of a dinuclear Mn(II)Mn(III) moiety, [Mn(III)(μ-HBPClNOL)(μ-BPClNOL)Mn(II)(Cl)](ClO4 )·2H2 O, 1 , in which the Mn ions are connected by two different bridging groups provided by two molecules of the ligand H2 BPClNOL, a phenoxide and an alkoxide group...
2018: Frontiers in Chemistry
Jianrong Steve Zhou, Xiaohu Zhao, Haiyan Xu, Xiaolei Huang
asymmetric reductive amination of poorly nucleophilic sulfonamides is realized in the presence of nickel catalysts and titanium alkoxide. A wide range of enolizable ketones, including some dialkyl and biaryl ketones, were converted in one pot to sulfonamides in excellent enantiomeric excess. The method is also applicable to cyclization of sulfamates and intermolecular reductive amination of a diarylphosphinamide. Formic acid was used as a safe and economic surrogate of high-pressure hydrogen gas.
October 30, 2018: Angewandte Chemie
Chunyan Zhang, Guoying Zhang, Shizhong Luo, Chunfu Wang, Huiping Li
A practical and efficient base-catalyzed esterification has been developed for the facile synthesis of a broad range of esters from simple alcohols with unactivated tert-butyl esters. This protocol could be conducted at mild conditions, providing esters in high to excellent yields with good functional tolerance. Mechanistic studies provided evidence of an exchange of the tert-butyl alkoxide metal with the alcohol, producing a new alkoxide to participate in the transesterification reaction.
November 14, 2018: Organic & Biomolecular Chemistry
Lauren E VanGelder, Brittney E Petel, Olaf Nachtigall, Gabriel Martinez, William W Brennessel, Ellen M Matson
The success of nonaqueous redox flow battery technology requires synthetic advances in charge carrier design to increase compatibility with organic solvents. Herein, previous discoveries related to the development of multimetallic charge carriers are built upon with the high-yielding syntheses of ether-functionalized polyoxovanadate-alkoxide clusters, [V6 O7 (OR)9 (OCH2 )3 CR'] (R=CH3 , C2 H5 ; R'=CH3 , CH2 OCH3 , CH2 OC2 H4 OCH3 ). Like their homoleptic congeners [V6 O7 (OR)12 ] (R=CH3 , C2 H5 ), these clusters exhibit four redox events, spanning nearly a two-volt window, and demonstrate rapid electron-transfer kinetics...
October 15, 2018: ChemSusChem
Xingzhou Peng, Marc Behl, Pengfei Zhang, Magdalena Mazurek-Budzyn Ska, Yakai Feng, Andreas Lendlein
Well-defined dihydroxy telechelic oligodepsipeptides (oDPs), which have a high application potential as building blocks for scaffold materials for tissue engineering applications or particulate carrier systems for drug delivery applications are synthesized by ring-opening polymerization (ROP) of morpholine-2,5-diones (MDs) catalyzed by 1,1,6,6-tetra-n-butyl-1,6-distanna-2,5,7,10-tetraoxacyclodecane (Sn(IV) alkoxide). In contrast to ROP catalyzed by Sn(Oct)2 , the usage of Sn(IV) alkoxide leads to oDPs, with less side products and well-defined end groups, which is crucial for potential pharmaceutical applications...
October 14, 2018: Macromolecular Bioscience
Britta Glowacki, Roman Pallach, Michael Lutter, Fabian Roesler, Hazem Alnasr, Cedreric Thomas, Dieter Schollmeyer, Klaus Jurkschat
The syntheses of amino alcohols MeN(CH2 CH2 CMe2 OH)2 (1), MeN(CMe2 CH2 OH)(CH2 CMe2 OH) (2), MeN(CH2 CH2 CH2 OH)(CH2 CMe2 OH) (3), MeN(CH2 CH2 CMe2 OH)(CH2 CMe2 OH) (4), MeN(CH2 CH2 CMe2 OH)(CH2 CH2 OH) (5), and MeN(CH2 CH2 OH) (CH2 CH2 CH2 OH) (6) as well as spirocyclic tin(IV) alkoxides spiro-[nBuN(CH2 CMe2 O)2 ]2 Sn (7), spiro-[MeN(CH2 CH2 CMe2 O)2 ]2 Sn (8), spiro-[para-FC6 H4 N (CH2 CMe2 O)2 ]2 Sn (9), spiro-[MeN(CMe2 CH2 O)(CH2 CMe2 O)]2 Sn (10), spiro-[MeN(CH2 CH2 CH2 O)(CH2 CMe2 O)]2 Sn (11), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CMe2 O)]2 Sn (12), spiro-[MeN(CH2 CH2 CMe2 O)(CH2 CH2 O)]2 Sn (13) and spiro-[MeN(CH2 CH2 O)(CH2 CH2 CH2 O)]2 Sn (14) are reported...
October 13, 2018: Chemistry: a European Journal
F Li, R L Meyer, S H Carpenter, L E VanGelder, A W Nichols, C W Machan, M L Neidig, E M Matson
A series of NO-bound, iron-functionalized polyoxovanadate-alkoxide (FePOV-alkoxide) clusters have been synthesized, providing insight into the role of multimetallic constructs in the coordination and activation of a substrate. Upon exposure of the heterometallic cluster to NO, the vanadium-oxide metalloligand is oxidized by a single electron, shuttling the reducing equivalent to the {FeNO} subunit to form a {FeNO}7 species. Four NO-bound clusters with electronic distributions ranging from [VV3VIV2]{FeNO}7 to [VIV5]{FeNO}7 have been synthesized, and characterized via 1 H NMR, infrared, and electronic absorption spectroscopies...
August 14, 2018: Chemical Science
Antoine Douchez, Azade Geranurimi, William D Lubell
γ,δ-Unsaturated ketones, so-called homoallylic ketones, have served as versatile building blocks for the synthesis of a variety of heterocycles, carbocycles, natural products, and reactive intermediates. Procured by a variety of processes, including conjugate addition of vinyl organometallic reagents to unsaturated ketones, allylation of silyl enol ethers, and rearrangements, homoallylic ketones are often synthesized by step-intensive methods. The cascade addition of 2 equiv of vinyl Grignard reagent to a carboxylate was reported by the Lubell laboratory in 2003 to give effective access to homoallylic ketones from a variety of aromatic, aliphatic, and α-amino methyl esters...
October 16, 2018: Accounts of Chemical Research
Lin Fang, Belén Albela, Boting Yang, Yuting Zheng, Peng Wu, Mingyuan He, Laurent Bonneviot
The reaction between titanium alkoxides, [Ti(OR)4 ], and surface silanol groups is widely used to generate grafted oxo-hydroxo titanium species, whose size is difficult to control. Partial capping of the surface silanols in the presence of the masking pattern of self-repelling tetramethylammonium ions allows us to isolate surface silanol islets, on which isolated titanium ions and dimeric oxo titanium species can be generated up to 2 Ti/Si mol %. Above this loading, and up to ∼8 Ti/Si mol %, higher oligomers (trimers, hexamers, octamers, and so on) are formed, reaching the size obtained at much lower loadings (<1 Ti/Si mol %) on a nonmodified silica surface...
October 30, 2018: Langmuir: the ACS Journal of Surfaces and Colloids
Fabrizio Monda, Robert Madsen
Zinc oxide has been developed as a catalyst for the dehydrogenation of primary alcohols into carboxylic acids and hydrogen gas. The reaction is performed in mesitylene solution in the presence of potassium hydroxide followed by workup with hydrochloric acid. The transformation can be applied to both benzylic and aliphatic primary alcohols and the catalytically active species was shown to be a homogeneous compound by a hot filtration test. Dialkylzinc and strongly basic zinc salts also catalyze the dehydrogenation with similar results...
October 1, 2018: Chemistry: a European Journal
Mark Abubekerov, Vojtěch Vlček, Junnian Wei, Matthias E Miehlich, Stephanie M Quan, Karsten Meyer, Daniel Neuhauser, Paula L Diaconescu
Neutral zinc alkoxide complexes show high activity toward the ring-opening polymerization of cyclic esters and carbonates, to generate biodegradable plastics applicable in several areas. Herein, we use a ferrocene-chelating heteroscorpionate complex in redox-switchable polymerization reactions, and we show that it is a moderately active catalyst for the ring-opening polymerization of L-lactide, ɛ-caprolactone, trimethylene carbonate, and δ-valerolactone. Uniquely for this type of catalyst, the oxidized complex has a similar polymerization activity as the corresponding reduced compound, but displays significantly different rates of reaction in the case of trimethylene carbonate and δ-valerolactone...
September 28, 2018: iScience
Johannes Teichert, Thomas Doert, Michael Ruck
The mechanisms of the polyol reduction of copper(ii) compounds were investigated by various systematic experiments. The course of the reduction in ethylene glycol strongly depends on the anion present in solution. Elemental copper can only be obtained in high yields starting from Cu(NO3)2, Cu(OAc)2, or Cu(OH)2; but not from CuCl2 or CuSO4. Intermediate compounds were observed, namely Cu2O, and the alkoxide compounds Cu(C2H4O2) and Cu3(OAc)2(C2H4O2)2. Cu3(OAc)2(C2H4O2)2 was characterised by single-crystal X-ray diffraction...
October 9, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Cecilia Agustín-Sáenz, Maider Machado, Agnieszka Tercjak
Porous silica layers with outstanding antireflective properties have been prepared by acid-catalyzed sol-gel process in presence of organic phases as structure directing agents (SDA) and excess water, with the aim of offering a cost-competitive, easy up-scaling and high efficiency process that contributes to reduce current levelized cost of energy (LCOE) of concentrating photovoltaics (CPV). The process has been optimized by controlling the water/alkoxide ratio, which is an important structure-regulating tool, having a strong influence in the structural properties of sol-gel synthesized materials...
January 15, 2019: Journal of Colloid and Interface Science
Francesca Becherini, Caterina Durante, Elsa Bourguignon, Mario Li Vigni, Vincent Detalle, Adriana Bernardi, Patrizia Tomasin
BACKGROUND AND METHODS: Wall paintings and architectural surfaces in outdoor environments are exposed to several physical, chemical and biological agents, hence they are often treated with different products to prevent or slow down their deterioration. Among the factors that have to be taken into account in the selection of the most suitable treatment for decorated surfaces, the aesthetic compatibility with the substrate is of great importance in the cultural heritage field; minimizing colour variation after treatment application is a crucial issue in particular for painted surfaces...
September 21, 2018: Chemistry Central Journal
Josiah J Newton, Robert Britton, Chadron M Friesen
Here we report a convenient synthesis of thionoesters by base-catalyzed transesterification. Benzyl and alkyl thionobenzoates and thionoheterobenzoates were efficiently prepared using various alcohols catalyzed by the corresponding sodium alkoxide. This methodology features a broad substrate scope, good to excellent yields, short reaction times, while simultaneously driving the reaction toward completion through the removal of the methanol byproduct. We also report the conversion of a small collection of thionobenzoates into the corresponding α,α-difluorobenzyl ethers to demonstrate the conversion of alcohols into difluorobenzyl or difluoroheterobenzyl ethers, a process that could prove useful for lead optimization in medicinal chemistry...
October 4, 2018: Journal of Organic Chemistry
Surja B Ghale, Jerry G Lanorio, Alex A Nickel, Kent M Ervin
The competitive threshold collision-induced dissociation technique is used to examine conformational effects on the relative gas-phase acidities of selected alcohols. By use of HF and H2 O as reference acids in a local thermochemical network to obtain absolute acidities, the measured 0 K gas-phase acidities for the propanol and pentanol isomers are Δacid H0 (CH3 CH2 CH2 O-H) = 1563.9 ± 2.9 kJ/mol, Δacid H0 ((CH3 )2 CHO-H) = 1568.2 ± 2.7 kJ/mol, Δacid H0 (CH3 (CH2 )4 O-H) = 1556.4 ± 2.9 kJ/mol, and Δacid H0 ((CH3 )2 CHCH2 CH2 O-H) = 1556...
October 4, 2018: Journal of Physical Chemistry. A
Zhe-Chen Wang, Ya-Ke Li, Sheng-Gui He, Veronica M Bierbaum
The strategy of synthesizing diazeniumdiolates (X-N(O)=NO- ) through the coexistence of nitric oxide and alkoxides (RO- ) was introduced by Wilhelm Traube 120 years ago. Today, despite the wide use of diazeniumdiolate derivatives to release nitric oxide in the treatment of cancer, the first step of the reaction mechanism for diazeniumdiolate synthesis remains a mystery and is thought to be complex. We have studied the gas-phase reactions of nitric oxide with alkoxides at room temperature. An electron-coupled hydrogen transfer is observed, and the radical anion HNO- is the only ionic product in these reactions...
September 6, 2018: European Journal of Mass Spectrometry
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