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41.
Lemaître F Lucas D Groison K Richard P Mugnier Y Harvey PD 《Journal of the American Chemical Society》2003,125(18):5511-5522
The stoichiometric and catalytic activations of alkyl halides and acid chlorides by the unsatured Pd(3)(dppm)(3)(CO)(2+) cluster (Pd(3)(2+)) are investigated in detail. A series of alkyl halides (R-X; R = t-Bu, Et, Pr, Bu, allyl; X = Cl, Br, I) react slowly with Pd(3)(2+) to form the corresponding Pd(3)(X)(+) adduct and "R(+)". This activation can proceed much faster if it is electrochemically induced via the formation of the paramagnetic species Pd(3)(+). The latter is the first confidently identified paramagnetic Pd cluster. The kinetic constants extracted from the evolution of the UV-vis spectra for the thermal activation, as well as the amount of electricity to bring the activation to completion for the electrochemically induced reactions, correlate the relative C-X bond strength and the steric factors. The highly reactive "R(+)" species has been trapped using phenol to afford the corresponding ether. On the other hand, the acid chlorides react rapidly with Pd(3)(2+) where no induction is necessary. The analysis of the cyclic voltammograms (CV) establishes that a dissociative mechanism operates (RCOCl --> RCO(+) + Cl(-); R = t-Bu, Ph) prior to Cl(-) scavenging by the Pd(3)(2+) species. For the other acid chlorides (R = n-C(6)H(13), Me(2)CH, Et, Me, Pr), a second associative process (Pd(3)(2+) + RCOCl --> Pd(3)(2+.....)Cl(CO)(R)) is seen. Addition of Cu(NCMe)(4)(+) or Ag(+) leads to the abstraction of Cl(-) from Pd(3)(Cl)(+) to form Pd(3)(2+) and the insoluble MCl materials (M = Cu, Ag) allowing to regenerate the starting unsaturated cluster, where the precipitation of MX drives the reaction. By using a copper anode, the quasi-quantitative catalytic generation of the acylium ion ("RCO(+)") operates cleanly and rapidly. The trapping of "RCO(+)" with PF(6)(-) or BF(4)(-) leads to the corresponding acid fluorides and, with an alcohol (R'OH), to the corresponding ester catalytically, under mild conditions. Attempts were made to trap the key intermediates "Pd(3)(Cl)(+)...M(+)" (M(+) = Cu(+), Ag(+)), which was successfully performed for Pd(3)(ClAg)(2+), as characterized by (31)P NMR, IR, and FAB mass spectrometry. During the course of this investigation, the rare case of PF(6)(-) hydrolysis has been observed, where the product PF(2)O(2)(-) anion is observed in the complex Pd(3)(PF(2)O(2))(+), where the substrate is well-located inside the cavity formed by the dppm-Ph groups above the unsatured face of the Pd(3)(2+) center. This work shows that Pd(3)(2+) is a stronger Lewis acid in CH(2)Cl(2) and THF than AlCl(3), Ag(+), Cu(+), and Tl(+). 相似文献
42.
Dierk Knittel 《Monatshefte für Chemie / Chemical Monthly》1982,113(1):37-41
The reaction of the electrolytically generated SO
2
–
anion radical with 1,-dihalides is used for the synthesis of sulfur containing heterocycles like oxathiolane-, oxathiane-, thiane- and thiepane-oxides. 1,2-Dihalides are reductively deblocked to give olefines.
Kathodische Reduktion von SO2 in Gegenwart organischer Dihalogenide
Zusammenfassung Die Reaktion des elektrolytisch erzeugten SO 2 – -Anionradikals mit 1,-Dihalogeniden führt zu schwefelhaltigen Heterocyclen wie Oxathiolan-, Oxathian-, Thian- und Thiepanoxiden. 1,2-Dihalogenide geben durch reduktive Eliminierung Olefine.相似文献
43.
Oren?Regev Jean-Fran?ois?Gohy Bas?G.?G.?Lohmeijer Sunil?K.?Varshney Dominique?H.?W.?Hubert Peter?M.?Frederik Ulrich?S.?SchubertEmail author 《Colloid and polymer science》2004,282(4):407-411
Metallo-supramolecular diblock copolymers consisting of a polystyrene (PS) block connected to a poly(ethylene oxide) (PEO) block by a bis(terpyridine)ruthenium complex (PS20-[Ru]-PEO
y
) were used to prepare aqueous micelles. The length of the PS block was kept constant, while two PEOs of different molecular weight were used. The resulting hydrated micelles and aggregates were characterized by a combination of cryogenic transmission electron microscopy (cryo-TEM) and dynamic light scattering measurements. The results were compared to those obtained for a covalent counterpart (PS22-b-PEO70). Cryogenic transmission electron microscopy allowed visualization of the PS core of the micelles. Moreover, the aggregates result from clustering of individual micelles. 相似文献
44.
B. Mahltig D. Knittel E. Schollmeyer H. Böttcher 《Journal of Sol-Gel Science and Technology》2004,31(1-3):293-297
The incorporation of triarylmethane dyes into sol–gel layers formed by modified silica was used for coating of textile materials. The coatings were performed with three triarylmethane dyes differ in electrical net charge and structure: The cationic dye Malachite Green, the anionic Guinea Green and the non-polar Reflex Blue 61. All coating procedures were performed using an acidic sol–gel process starting from a solution of tetraethoxysilane (TEOS) and the dye in a mixture of water and ethanol. Depositions were performed on polyester, polyamide and cotton textiles. Investigation of leaching and photobleaching fastness showed that the stability of the dyes was enhanced by incorporation into the silica layer. Sufficient leaching fastness was only achieved with the cationic dye due to direct attractive electrostatic interaction with the negatively charged silica matrix. Also the addition of a small amount of epoxysilane to the silica sols lead to an enhancement of leaching and bleaching fastness. 相似文献
45.
Alain Valla Benoist Valla Régis Le Guillou Dominique Cartier Laurent Dufossé Roger Labia 《Helvetica chimica acta》2007,90(3):512-520
Since the C15 β‐end‐group aldehyde 10 ((β‐ionylidene)acetaldehyde), an excellent intermediate in the syntheses of retinoids, can be synthesized in many ways from β‐ionone, and since the corresponding acyclic C15 ψ‐end‐group aldehyde 5 can easily be synthesized from citral ( 1 ) (Scheme 3), we applied the C15+C5 route to the syntheses of γ‐retinal ((all‐E)‐ 8 ) (Scheme 3) and retinal ((all‐E)‐ 13 ) (Scheme 4), and therefore, by coupling (2×C20→C40), to the preparation of lycopene ( 14 ) and β‐carotene ( 15 ) (Scheme 5). Our new syntheses of retinal ((all‐E)‐ 13 ) and γ‐retinal ((all‐E)‐ 8 use an extended aldol reaction with a C6 building block that incorporates a C5 unit after decarboxylation. 相似文献
46.
[reaction: see text] SIBX is a nonexplosive formulation of IBX that can be used as a suspension in a variety of standard organic solvents such as refluxing EtOAc and THF to oxidize safely alcohols into aldehydes and ketones. The use of hot THF is limited to the oxidation of allylic and benzylic alcohols. Most yields are comparable to those obtained with IBX or DMP. SIBX can also be used to perform oxygenative demethylation of 2-methoxyarenols into orthoquinones and catechols. 相似文献
47.
Ahmad Sarakbi Zeynep AydogmusAngela Dago Dominique MertensJean-Yves Dewert Jean-Michel Kauffmann 《Analytica chimica acta》2013
Liquid chromatography coupled to a silver electrode based flow-through amperometric detector (LC-EC-Ag) was developed for the determination of aminothiols in white wines. The C18 reversed phase LC system operated in the isocratic mode at 0.7 mL min−1 and used an acidic mobile phase composed of formic acid, EDTA, sodium nitrate, sodium hydroxide, and methanol 1% (v/v) at pH 4.5. The working electrode operated at 0.08 V vs Ag/AgCl, 3 M KCl and its manual cleaning was realized once a month by smoothing on a polishing cloth. The analyzed aminothiols were resolved and eluted within 4 min, and all standard curves were linear in the range 2 × 10−7–2 × 10−5 M. The analyzed wine samples needed no preparation other than dilution with the mobile phase. The concentration of cysteine (CYS), homocysteine (HCYS), glutathione (GSH) and N-acetylcysteine (NAC) in bottled white wines, determined by the method of standard addition, was found to be in the low μM range (0.2–2 mg L−1) depending on the wine type and its age. 相似文献
48.
49.
Dr. Ting Liang Dr. Dominique Collin Melodie Galerne Dr. Gad Fuks Dr. Andreas Vargas Jentzsch Prof. Dr. Mounir Maaloum Alain Carvalho Prof. Dr. Nicolas Giuseppone Dr. Emilie Moulin 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14341-14348
C3-Symmetric triarylamine trisamides (TATAs), decorated with three norbornene end groups, undergo supramolecular polymerization and further gelation by π–π stacking and hydrogen bonding of their TATA cores. By using subsequent ring-opening metathesis polymerization, these physical gels are permanently crosslinked into chemical gels. Detailed comparisons of the supramolecular stacks in solution, in the physical gel, and in the chemical gel states, are performed by optical spectroscopies, electronic spectroscopies, atomic force microscopy, electronic paramagnetic resonance spectroscopy, X-ray scattering, electronic transport measurements, and rheology. The results presented here clearly evidence that the core structure of the functional supramolecular polymers can be precisely retained during the covalent capture whereas the mechanical properties of the gels are concomitantly improved, with an increase of their storage modulus by two orders of magnitude. 相似文献
50.
Róbert Bordás Volker John Ellen Schmeyer Dominique Thévenin 《Theoretical and Computational Fluid Dynamics》2013,27(3-4):253-271
The droplet size distribution in a turbulent flow field is considered and modeled by means of a population balance system. This paper studies different numerical methods for the 4D population balance equation and their impact on an output of interest, the time-space-averaged droplet size distribution at the outlet, which is known from experiments. These methods include different interpolations of the experimental data at the inlet, various discretizations in time and space, and different schemes for computing the coalescence integrals. It will be shown that noticeable changes in the output of interest might occur. In addition, the computational efficiency of the studied methods is discussed. 相似文献