1825-62-3Relevant articles and documents
NMR DETERMINATION OF ABSOLUTE SITE-SPECIFIC NATURAL ISOTOPE RATIOS OF HYDROGEN IN ORGANIC MOLECULES. ANALYTICAL AND MECHANISTIC APPLICATIONS
Martin, G. J.,Sun, X. Y.,Guillou, C.,Martin, M. L.
, p. 3285 - 3296 (1985)
It has been shown that the "internal" isotope distribution within a given molecular species at the natural abundance level is accessible by a new method, SNIF-nmr, which is based on deuterium NMR.Relative internal factors, Ri/j, have been defined which enable the isotope content of a given site, i, to be compared to that of another molecular site, j, taken as a reference.Several referencing methods intended to provide direct access to relative externals, Ti, and absolute, (D/H), site-specific parameters, are now discussed from both the theoretical and the experimental points of wiev.In the intramolecular referencing method, which involves a time-consuming chemical transformation of the sample, the risk exists of more or less systematic errors resulting from discriminating fractionation effects.However this technique offers, conversely, an interesting way of investigating kinetic isotope effects without the need for specific labelling.In spite of its lower spectral precision the external referencing method has the advantage of being fast and less sensitive to systemetic errors and may be used for direct rough routine determinations of the site-specific isotope contents.More precise results can be obtained, at the price of contaminating the sample, when an intermolecular reference is added and signal heights are used, remembering however that the intensity parameters then have no strict physical meaning in terms of absolute isotope contents.The site-specific parameters, Ti and (D/H)i thus accessible, provide new information on the mechanisms of the fractionation effects occuring in natural conditions and exaples are considered.
Synthesis and thermal transformations of polyphosphosiloxane based on trimethyl phosphate and (3-aminopropyl)triethoxysilane
Klement'eva,Cherepennikova,Semenov,Kirillov,Lopatin,Kuznetsova,Kurskii,Zaitsev,Klapshina,Duglas,Domrachev
, p. 2214 - 2224 (2007)
A method for the synthesis of polyphosphosiloxane by the thermal condensation of an equimolar mixture of trimethyl phosphate and (3-aminopropyl)triethoxysilane at 200 °C was developed. The reaction affords ethanol and polyphosphosiloxane-{Si(OEt)[(CH
Unimolecular Decomposition of Ethoxytrimethylsilane
Herold, David A.,Furtell, Jean H.
, p. 984 - 988 (1989)
A study of the metastable spectra from ethoxytrimethylsilane and the mass shifts of the deuterium-labeled species permitted the rationalization of the fragmentation mechanism for forming all major ions in the mass spectrum.A new mechanistic pathway for th
Catalytic Enantioselective Strecker Reaction of Isatin-Derived N-Unsubstituted Ketimines
Kadota, Tetsuya,Sawa, Masanao,Kondo, Yuta,Morimoto, Hiroyuki,Ohshima, Takashi
supporting information, p. 4553 - 4558 (2021/06/28)
A catalytic enantioselective Strecker reaction of isatin-derived N-unsubstituted ketimines directly afforded the N-unprotected α-aminonitriles with a tetrasubstituted carbon stereocenter in up to 99% ee without requiring protection/deprotection steps. One-pot Strecker reactions from the parent carbonyl compounds were also realized with comparable yields and enantioselectivities. Direct transformations of the N-unprotected α-aminonitrile products streamlined the synthesis of unnatural amino acid derivatives and achieved the shortest one-pot stereoselective routes to a biologically active compound reported to date.
Sustainable Catalytic Synthesis of Diethyl Carbonate
Putro, Wahyu S.,Ikeda, Akira,Shigeyasu, Shinji,Hamura, Satoshi,Matsumoto, Seiji,Lee, Vladimir Ya.,Choi, Jun-Chul,Fukaya, Norihisa
, p. 842 - 846 (2020/12/07)
New sustainable approaches should be developed to overcome equilibrium limitation of dialkyl carbonate synthesis from CO2 and alcohols. Using tetraethyl orthosilicate (TEOS) and CO2 with Zr catalysts, we report the first example of sustainable catalytic synthesis of diethyl carbonate (DEC). The disiloxane byproduct can be reverted to TEOS. Under the same conditions, DEC can be synthesized using a wide range of alkoxysilane substrates by investigating the effects of the number of ethoxy substituent in alkoxysilane substrates, alkyl chain, and unsaturated moiety on the fundamental property of this reaction. Mechanistic insights obtained by kinetic studies, labeling experiments, and spectroscopic investigations reveal that DEC is generated via nucleophilic ethoxylation of a CO2-inserted Zr catalyst and catalyst regeneration by TEOS. The unprecedented transformation offers a new approach toward a cleaner route for DEC synthesis using recyclable alkoxysilane.
Metal-Free Catalytic Reductive Cleavage of Enol Ethers
Chulsky, Karina,Dobrovetsky, Roman
supporting information, p. 6804 - 6807 (2018/11/02)
In contrast to the well-known reductive cleavage of the alkyl-O bond, the cleavage of the alkenyl-O bond is much more challenging especially using metal-free approaches. Unexpectedly, alkenyl-O bonds were reductively cleaved when enol ethers were reacted with Et3SiH and a catalytic amount of B(C6F5)3. Supposedly, this reaction is the result of a B(C6F5)3-catalyzed tandem hydrosilylation reaction and a silicon-assisted β-elimination. A mechanism for this cleavage reaction is proposed based on experiments and density functional theory (DFT) calculations.
Application of a novel nano-immobilization of ionic liquid on an MCM-41 system for trimethylsilylation of alcohols and phenols with hexamethyldisilazane
Zolfigol, Mohammad Ali,Sajjadifar, Sami,Ghorbani-Choghamarani, Arash,Tami, Farzaneh
, p. 7093 - 7106 (2018/08/17)
3-[(3-(Trisilyloxy)propyl)chloride]-1-methylimidazolium tribromide ionic liquid supported on MCM-41 [nano-MCM-41@(CH2)3-1-methylimidazole]Br3 as a novel heterogeneous nano-catalyst was easily prepared and characterized usi
Preparation of tetrafluoroethylene from the pyrolysis of pentafluoropropionate salts
Hercules, Daniel A.,Parrish, Cameron A.,Sayler, Todd S.,Tice, Kevin T.,Williams, Shane M.,Lowery, Lauren E.,Brady, Michael E.,Coward, Robert B.,Murphy, Justin A.,Hey, Trevyn A.,Scavuzzo, Anthony R.,Rummler, Lucy M.,Burns, Emory G.,Matsnev, Andrej V.,Fernandez, Richard E.,McMillen, Colin D.,Thrasher, Joseph S.
, p. 107 - 116 (2017/04/18)
The use of tetrafluoroethylene (TFE) in academic institutions beyond a few millimoles has often been inhibited by the compound's inherent danger and general lack of commercial availability. On the other hand, TFE is prepared industrially on a rather large scale by a number of major fluorochemical companies via the pyrolysis of chlorodifluoromethane at high temperatures, yielding TFE and HCl. For a few years at The University of Alabama and Clemson University, we have been preparing TFE on a 100+-gram scale by the pyrolysis under dynamic vacuum of pentafluoropropionate salts, which can be obtained from the neutralization of pentafluoropropionic acid with a M(OH)n (where M?=?Li, Na, K, and Cs for n?=?1 and Mg, Ca, and Ba for n?=?2). Additionally, potassium pentafluoropropionate can be prepared from the reaction of potassium trimethylsilanolate and ethyl pentafluoropropionate. The pentafluoropropionate salts and their decomposition products have been characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), accelerating rate calorimetry (ARC), nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, Fourier transform-infrared (FTIR) spectrophotometry, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDAX), X-ray diffraction (XRD), and single-crystal X-ray crystallography, where applicable. Typical yields of TFE obtained from pyrolysis of potassium pentafluoropropionate obtained from the acid-base neutralization method are >98%, while yields of TFE from the same salt prepared by the silanolate method from ethyl pentafluoropropionate are ca. 80%.
One-Step Synthesis of Siloxanes from the Direct Process Disilane Residue
Neumeyer, Felix,Auner, Norbert
supporting information, p. 17165 - 17168 (2016/11/23)
The well-established Müller–Rochow Direct Process for the chloromethylsilane synthesis produces a disilane residue (DPR) consisting of compounds MenSi2Cl6?n(n=1–6) in thousands of tons annually. Technologically, much effort is made to retransfer the disilanes into monosilanes suitable for introduction into the siloxane production chain for increase in economic value. Here, we report on a single step reaction to directly form cyclic, linear, and cage-like siloxanes upon treatment of the DPR with a 5 m HCl in Et2O solution at about 120 °C for 60 h. For simplification of the Si?Si bond cleavage and aiming on product selectivity the grade of methylation at the silicon backbone is increased to n≥4. Moreover, the HCl/Et2O reagent is also suitable to produce siloxanes from the corresponding monosilanes under comparable conditions.
ELECTROLYTE FORMULATIONS CONTAINING CYANO-ALKOXY-BORATE ANIONS
-
Page/Page column 59-60, (2012/04/17)
The present invention relates to electrolyte formulations containing cyano-alkoxy-borate anions, their preparation and their use, in particular as part of electrolyte formulations for electrochemical or optoelectronic devices and special compounds containing cyano-alkoxy-borate anions.
