scholarly journals Electrochemical generation of 2,3-oxazolidinone glycosyl triflates as an intermediate for stereoselective glycosylation

2012 ◽  
Vol 8 ◽  
pp. 456-460 ◽  
Author(s):  
Toshiki Nokami ◽  
Akito Shibuya ◽  
Yoshihiro Saigusa ◽  
Shino Manabe ◽  
Yukishige Ito ◽  
...  
Keyword(s):  
Low Temperature ◽  
Electrochemical Oxidation ◽  
Low Temperatures ◽  
Protecting Group ◽  
Triflic Acid ◽  
Electrochemical Generation ◽  
Stereoselective Glycosylation

Glycosyl triflates with a 2,3-oxazolidinone protecting group were generated from thioglycosides by low-temperature electrochemical oxidation. The glycosyl triflates reacted with alcohols to give the corresponding glycosides β-selectively at low temperatures. However, α-selectivity was observed in the absence of base at elevated reaction temperatures. In situ generated triflic acid promotes the isomerization of β-products to α-products.

In situ Tensile Experiments at Low Temperatures on Niobium Single Crystals by H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 58-59
Author(s):  
F. H. Louchet ◽  
L. P. Kubin
Keyword(s):  
Electron Microscope ◽  
Transition Temperature ◽  
Low Temperature ◽  
Slip System ◽  
Low Temperatures ◽  
Tensile Axis ◽  
Image Intensifier ◽  
Screw Dislocations ◽  
Source Operation

Experiments have been carried out on the 3 MeV electron microscope in Toulouse. The low temperature straining holder has been previously described Images given by an image intensifier are recorded on magnetic tape.The microtensile niobium samples are cut in a plane with the two operative slip directions [111] and lying in the foil plane. The tensile axis is near [011].Our results concern:- The transition temperature of niobium near 220 K: at this temperature and below an increasing difference appears between the mobilities of the screw and edge portions of dislocations loops. Source operation and interactions between screw dislocations of different slip system have been recorded.

Kinetically asymmetric charge and discharge behavior of LiNi0.5Mn1.5O4 at low temperature observed by in situ X-ray diffraction

2014 ◽  
Vol 2 (37) ◽  
pp. 15414-15419 ◽  
Author(s):  
Ikuma Takahashi ◽  
Haruno Murayama ◽  
Kenji Sato ◽  
Takahiro Naka ◽  
Koji Kitada ◽  
...  
Keyword(s):  
Low Temperature ◽  
Low Temperatures ◽  
X Ray Diffraction ◽  
X Ray ◽  
Discharge Behavior

Thermodynamically reversible LiNi0.5Mn1.5O4 electrodes kinetically behave asymmetrically during charging and discharging at low temperatures.

Low temperature in situ Raman spectroscopy of an electro-generated arylbis(arylthio)sulfonium ion

2015 ◽  
Vol 51 (66) ◽  
pp. 13106-13109 ◽  
Author(s):  
Kouichi Matsumoto ◽  
Yu Miyamoto ◽  
Kazuaki Shimada ◽  
Yusuke Morisawa ◽  
Hendrik Zipse ◽  
...  
Keyword(s):  
Organic Chemistry ◽  
Raman Spectroscopy ◽  
Low Temperature ◽  
Electrochemical Oxidation ◽  
Reactive Intermediate ◽  
In Situ Raman Spectroscopy ◽  
In Situ Raman

Low temperature in situ Raman spectroscopy detects reactive intermediate cations generated by the electrochemical oxidation in organic chemistry.

The Selective Epitaxy of Silicon at Low Temperatures

1991 ◽  
Vol 220 ◽  
Author(s):  
Jen-Chung Lou ◽  
William G. Oldham ◽  
Harry Kawayoshi ◽  
Peiching Ling
Keyword(s):  
Growth Rate ◽  
Low Temperature ◽  
Low Temperatures ◽  
Surface Oxide ◽  
Ex Situ ◽  
Deposition Cycle ◽  
Local Growth ◽  
Selective Epitaxial Growth

ABSTRACTLow-temperature selective epitaxial growth (SEG) of silicon using a dichlorosilane-hydrogen mixture in an LPCVD hot-wall reactor has been discussed with respect to the wafer preparation and the deposition cycle. The surface morphology and the quality of epilayers are strongly affected by residual oxide islands at interface. A reduction of local growth rate near interfacial oxides is attributed to the dissolution of oxide at interface, and this reduction can lead to pits and textured features on the Si epitaxial surface. An ex-situ HF vapor or an HF dip with an in-situ small DCS 900°C prebake step can completely remove surface oxide prior to the deposition and achieve defect-free Si epilayers at the deposition temperatures of 850°C and 800°C. It is also found that fluorine atoms can play a major role in the removal of surface oxide.

A Synthetic Pathway to Arylsilyl(silyl)arenes; Selective Si-C Cleavage in Bis(arylsilyl)arenes with Triflic Acid

1995 ◽  
Vol 50 (4) ◽  
pp. 613-618 ◽  
Author(s):  
Robert Schröck ◽  
Klaus Angermaier ◽  
Hubert Schmidbaur
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Low Temperatures ◽  
Triflic Acid ◽  
X Ray Diffraction ◽  
Synthetic Pathway ◽  
X Ray ◽  
Grignard Reactions

Bis(arylsilyl)arenes such as bis(p-tolylsilyl)benzene and bis(p-anisylsilyl)naphthalene are available from in situ Grignard reactions of the corresponding haloarenes, arylchlorosilanes and magnesium in tetrahydrofuran. Treatment of these products with one equivalent of trifluoromethanesulfonic (triflic) acid at low temperatures leads to arylsilyl(trifluoromethylsulfonatosilyl) arenes, which can be converted into arylsilyl(silyl)arenes using LiAlH4. The regioselectivity of the Si - C cleavage is surprisingly high. Any of the first dearylation steps is faster then the consecutive steps. Ortho, meta and para substituted p-tolylsilyl(silyl)benzenes, 1,4-dibromo-2-(p-tolylsilyl)-5-(silyl)benzene, and 1-(p-anisylsilyl)-8-(silyl)naphthalene have thus been obtained in good to moderate yields. These compounds can serve as starting materials for monofunctional arylsilanes with a tailored structure. The crystal structure of 1-(p-anisylsiIyI)-8-(siIyl)naphthalene has been determined by single crystal X-ray diffraction.

Role of boundaries in the crystallization of amorphous films

1988 ◽  
Vol 46 ◽  
pp. 626-627
Author(s):  
D. A. Smith
Keyword(s):  
Low Temperature ◽  
Amorphous State ◽  
Nucleation And Growth ◽  
Amorphous Films ◽  
Island Nucleation ◽  
Surface Steps ◽  
Transmission Electron ◽  
Component Systems ◽  
Temperature Deposition

The nucleation and growth processes which lead to the formation of a thin film are particularly amenable to investigation by transmission electron microscopy either in situ or subsequent to deposition. In situ studies have enabled the observation of island nucleation and growth, together with addition of atoms to surface steps. This paper is concerned with post-deposition crystallization of amorphous alloys. It will be argued that the processes occurring during low temperature deposition of one component systems are related but the evidence is mainly indirect. Amorphous films result when the deposition conditions such as low temperature or the presence of impurities (intentional or unintentional) preclude the atomic mobility necessary for crystallization. Representative examples of this behavior are CVD silicon grown below about 670°C, metalloids, such as antimony deposited at room temperature, binary alloys or compounds such as Cu-Ag or Cr O2, respectively. Elemental metals are not stable in the amorphous state.

“In-Situ Raman Spectroscopy of Electronic Processes in Fullerene Thin Films

2002 ◽  
Vol 725 ◽  
Author(s):  
S.B. Phelan ◽  
B.S. O'Connell ◽  
G. Farrell ◽  
G. Chambers ◽  
H.J. Byrne
Keyword(s):  
Thin Film ◽  
Indium Tin Oxide ◽  
Low Temperatures ◽  
In Situ Raman Spectroscopy ◽  
State Reduction ◽  
In Situ Raman ◽  
Linear Behavior ◽  
Current Voltage ◽  
Solid State Reduction

AbstractThe current voltage characteristics of C60 thin film sandwich structures fabricated by vacuum deposition on indium tin oxide (ITO) with an aluminium top electrode are presented and discussed. A strongly non-linear behavior and a sharp increase in the device conductivity was observed at relatively low voltages (∼2V), at both room and low temperatures (20K). At room temperature the system is seen to collapse, and in situ Raman measurements indicate a solid state reduction of the fullerene thin film to form a polymeric state. The high conductivity state was seen to be stable at elevated voltages and low temperatures. This state is seen to be reversible with the application of high voltages. At these high voltages the C60 film was seen to sporadically emit white light at randomly localized points analogous to the much documented Electroluminescence in single crystals.

INVAR M93

Alloy Digest ◽  
2008 ◽  
Vol 57 (1) ◽  
Keyword(s):  
Fracture Toughness ◽  
Low Temperature ◽  
Physical Properties ◽  
Tensile Properties ◽  
Low Temperatures ◽  
Bend Strength ◽  
Temperature Performance ◽  
Ni Content ◽  
Precision Alloys ◽  
Ni Alloy

Abstract Invar is an Fe-Ni alloy with 36% Ni content that exhibits the lowest expansion of known metals from very low temperatures up to approximately 230 deg C (445 deg F). Invar M93 is a cryogenic Invar with improved weldability. This datasheet provides information on composition, physical properties, hardness, elasticity, tensile properties, and shear and bend strength as well as fracture toughness and fatigue. It also includes information on low temperature performance as well as forming and joining. Filing Code: FE-143. Producer or source: Metalimphy Precision Alloys.

Indium Bromide-catalyzed Unprecedented Hydrogenolysis: A Novel One-Pot Synthesis of Per-O-Acetylated β-carboxymethyl O and S-glycosides

2020 ◽  
Vol 24 (8) ◽  
pp. 900-908
Author(s):  
Ram Naresh Yadav ◽  
Amrendra K Singh ◽  
Bimal Banik
Keyword(s):  
Asymmetric Synthesis ◽  
Chiral Auxiliary ◽  
Bioactive Molecules ◽  
One Pot ◽  
Enantiomerically Pure ◽  
Stereoselective Glycosylation ◽  
One Pot Synthesis ◽  
Wide Range

Numerous O (oxa)- and S (thia)-glycosyl esters and their analogous glycosyl acids have been accomplished through stereoselective glycosylation of various peracetylated bromo sugar with benzyl glycolate using InBr3 as a glycosyl promotor followed by in situ hydrogenolysis of resulting glycosyl ester. A tandem glycosylating and hydrogenolytic activity of InBr3 has been successfully investigated in a one-pot procedure. The resulting synthetically valuable and virtually unexplored class of β-CMGL (glycosyl acids) could serve as an excellent potential chiral auxiliary in the asymmetric synthesis of a wide range of enantiomerically pure medicinally prevalent β-lactams and other bioactive molecules of diverse medicinal interest.

Properties of electrochemically generated primary cationradicals of phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles

1980 ◽  
Vol 45 (6) ◽  
pp. 1669-1676 ◽  
Author(s):  
Pavel Kubáček
Keyword(s):  
Electrochemical Oxidation ◽  
Spin Polarization ◽  
High Spin ◽  
Epr Spectroscopy ◽  
Half Life ◽  
Electrochemical Behaviour ◽  
Epr Spectra ◽  
Electrochemical Generation ◽  
Splitting Constant ◽  
Reduced Temperature

The first step of electrochemical oxidation of 2-phenyl- and 2-(4-tolyl)-1,3,4,7-tetramethylisoindoles in anhydrous acetonitrile produces relatively stable cationradicals which have been studied by means of EPR spectroscopy using the method of internal electrochemical generation of radicals under reduced temperature. The same electrochemical behaviour of the both studied derivatives and identical EPR spectra of their cationradicals can be explained within the Huckel MO method. The largest contribution to the magnitude of splitting constant of nitrogen nucleus is due to π-σ-spin polarization of C-N bonds caused by high spin abundance of pz-AO of carbon atoms. Half-life of decomposition of the studied cationradicals is 4 min at -30°C.

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