scholarly journals Copper-catalyzed olefinic C–H difluoroacetylation of enamides

2014 ◽  
Vol 50 (44) ◽  
pp. 5887-5890 ◽  
Author(s):  
Gilles Caillot ◽  
Jérémy Dufour ◽  
Marie-Charlotte Belhomme ◽  
Thomas Poisson ◽  
Laurence Grimaud ◽  
...  
Keyword(s):  
Regioselective Synthesis ◽  
First Time

An efficient copper-catalyzed method for the regioselective synthesis of β-difluoroester substituted enamides using BrCF2CO2Et is reported for the first time.

W(CO)3(Ph2PC2H4PPh2)(η2-Sc3N@Ih-C80/Sc3N@D5h-C80): regioselective synthesis and crystallographic characterization of air-stable mononuclear complexes of endohedral fullerenes

2016 ◽  
Vol 45 (29) ◽  
pp. 11606-11610 ◽  
Author(s):  
Lipiao Bao ◽  
Bin Liu ◽  
Xiaofang Li ◽  
Changwang Pan ◽  
Yunpeng Xie ◽  
...  
Keyword(s):  
Coordination Complexes ◽  
Regioselective Synthesis ◽  
Endohedral Fullerenes ◽  
Endohedral Metallofullerenes ◽  
Mononuclear Complexes ◽  
First Time

Air-stable mononuclear coordination complexes of endohedral metallofullerenes have been regioselectively synthesized and crystallographically characterized for the first time.

Regioselective synthesis of salicylates and acetophenones by formal [3+3]-cyclocondensations of 3-oxoorthoesters with 1,3-bis(trimethylsilyloxy)-1,3-butadienes

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Jörg-Peter Gütlein ◽  
Mathias Lubbe ◽  
Holger Feist ◽  
Alexander Villinger ◽  
Peter Langer
Keyword(s):  
Regioselective Synthesis ◽  
First Time

AbstractA variety of 4-methoxysalicylates and related polyketide-type phenols are regioselectively prepared by formal [3+3] cyclocondensations of 1,3-bis(trimethylsilyloxy)-1,3-butadienes with 3-oxo-orthoesters. Cycloalkyl-substituted salicylates were prepared for the first time.

The Regioselective Synthesis of o-Nitrobenzyl DOPA Derivatives

Synthesis ◽  
2017 ◽  
Vol 49 (12) ◽  
pp. 2691-2699 ◽  
Author(s):  
Tobias Schneider ◽  
Joshua Martin ◽  
Patrick Durkin ◽  
Vladimir Kubyshkin ◽  
Nediljko Budisa
Keyword(s):  
Synthetic Peptides ◽  
Biological Systems ◽  
New Method ◽  
Regioselective Synthesis ◽  
Non Invasive ◽  
Efficient Control ◽  
Synthetic Routes ◽  
Adhesive Proteins ◽  
First Time ◽  
Catechol Moiety

Photocaged DOPA derivatives may serve for non-invasive unmasking of the catechol fragment in biological systems. This would enable efficient control of the redox and metal-coordinating properties associated with the free catechol moiety, in particular, in biosynthetically produced adhesive proteins and synthetic peptides. Synthetic routes towards photocaged DOPA derivatives are reported herein. A new method for preparing para-alkylated DOPA starting from 3,4-dihydroxybenzaldehyde is described for the first time.

Regioselective synthesis of polycyclic sulfones via radical-induced three-component bicyclization cascades

2019 ◽  
Vol 55 (22) ◽  
pp. 3227-3230 ◽  
Author(s):  
Xiao-Yan Qin ◽  
Long He ◽  
Jing Li ◽  
Wen-Juan Hao ◽  
Shu-Jiang Tu ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Regioselective Synthesis ◽  
Internal Alkynes ◽  
First Time

New radical-triggered three-component bicyclization cascades of 2-alkynylaryldiazonium tetrafluoroborates with a sulfur dioxide surrogate DABCO·(SO2)2 and internal alkynes have been reported for the first time, leading to 49 examples of polycyclic sulfones with moderate to good yields.

scholarly journals Regioselective synthesis of heterocyclic N-sulfonyl amidines from heteroaromatic thioamides and sulfonyl azides

2020 ◽  
Vol 16 ◽  
pp. 2937-2947
Author(s):  
Vladimir Ilkin ◽  
Vera Berseneva ◽  
Tetyana Beryozkina ◽  
Tatiana Glukhareva ◽  
Lidia Dianova ◽  
...  
Keyword(s):  
Regioselective Synthesis ◽  
Dimroth Rearrangement ◽  
Sulfonyl Azides ◽  
Reliable Procedure ◽  
First Time ◽  
Heterocyclic Thioamides ◽  
Heteroaromatic Thioamides

N-Sulfonyl amidines bearing 1,2,3-triazole, isoxazole, thiazole and pyridine substituents were successfully prepared for the first time by reactions of primary, secondary and tertiary heterocyclic thioamides with alkyl- and arylsulfonyl azides. For each type of thioamides a reliable procedure to prepare N-sulfonyl amidines in good yields was found. Reactions of 1-aryl-1,2,3-triazole-4-carbothioamides with azides were shown to be accompanied with a Dimroth rearrangement to form 1-unsubstituted 5-arylamino-1,2,3-triazole-4-N-sulfonylcarbimidamides. 2,5-Dithiocarbamoylpyridine reacts with sulfonyl azides to form a pyridine bearing two sulfonyl amidine groups.

Annulate lamellae in the Sertoli cells of guinea pig testis after unilateral torsion of the spermatic cord

1984 ◽  
Vol 42 ◽  
pp. 196-197
Author(s):  
J. Chakraborty ◽  
A. P. Sinha Hikim ◽  
J. S. Jhunjhunwala
Keyword(s):  
Sertoli Cells ◽  
Guinea Pigs ◽  
Spermatic Cord ◽  
Present Report ◽  
Cell Types ◽  
Annulate Lamellae ◽  
Spermatogenic Cells ◽  
Electron Microscopic ◽  
Structural Details ◽  
First Time

Although the presence of annulate lamellae was noted in many cell types, including the rat spermatogenic cells, this structure was never reported in the Sertoli cells of any rodent species. The present report is based on a part of our project on the effect of torsion of the spermatic cord to the contralateral testis. This paper describes for the first time, the fine structural details of the annulate lamellae in the Sertoli cells of damaged testis from guinea pigs.One side of the spermatic cord of each of six Hartly strain adult guinea pigs was surgically twisted (540°) under pentobarbital anesthesia (1). Four months after induction of torsion, animals were sacrificed, testes were excised and processed for the light and electron microscopic investigations. In the damaged testis, the majority of seminiferous tubule contained a layer of Sertoli cells with occasional spermatogonia (Fig. 1). Nuclei of these Sertoli cells were highly pleomorphic and contained small chromatinic clumps adjacent to the inner aspect of the nuclear envelope (Fig. 2).

Electron spectroscopic imaging and diffraction

1991 ◽  
Vol 49 ◽  
pp. 706-707
Author(s):  
M. Rühle ◽  
J. Mayer ◽  
J.C.H. Spence ◽  
J. Bihr ◽  
W. Probst ◽  
...  
Keyword(s):  
Materials Science ◽  
Electron Spectroscopic Imaging ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Illumination System ◽  
Probe Size ◽  
Diffraction Patterns ◽  
Fritz Haber ◽  
Koehler Illumination ◽  
First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

A Novel TEM Technique for Characterizing As-Grown CVD Diamond Films

1991 ◽  
Vol 49 ◽  
pp. 956-957 ◽  
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Diamond Films ◽  
Chemical Vapor ◽  
Growth Direction ◽  
Dark Field ◽  
Growth Surface ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
First Time ◽  
Microstructural Studies

Microstructural studies by transmission electron microscopy (TEM) of diamond films grown by chemical vapor deposition (CVD) usually involve tedious specimen preparation. This process has been avoided with a technique that is described in this paper. For the first time, thick as-grown diamond films have been examined directly in a conventional TEM without thinning. With this technique, the important microstructures near the growth surface have been characterized. An as-grown diamond film was fractured on a plane containing the growth direction. It took about 5 min to prepare a sample. For TEM examination, the film was tilted about 30-45° (see Fig. 1). Microstructures of the diamond grains on the top edge of the growth face can be characterized directly by transmitted electron bright-field (BF) and dark-field (DF) images and diffraction patterns.

A microscopic marker experiment study on high temperature oxidation of Ni-Al alloy

1986 ◽  
Vol 44 ◽  
pp. 514-515
Author(s):  
Shou-kong Fan
Keyword(s):  
Transport Mechanism ◽  
High Temperature Oxidation ◽  
Transverse Section ◽  
Al Alloy ◽  
Metal Interface ◽  
Electron Microscopic ◽  
Temperature Oxidation ◽  
Analytical Electron ◽  
Microscopic Studies ◽  
First Time

Transmission and analytical electron microscopic studies of scale microstructures and microscopic marker experiments have been carried out in order to determine the transport mechanism in the oxidation of Ni-Al alloy. According to the classical theory, the oxidation of nickel takes place by transport of Ni cations across the scale forming new oxide at the scale/gas interface. Any markers deposited on the Ni surface are expected to remain at the scale/metal interface after oxidation. This investigation using TEM transverse section techniques and deposited microscopic markers shows a different result,which indicates that a considerable amount of oxygen was transported inward. This is the first time that such fine-scale markers have been coupled with high resolution characterization instruments such as TEM/STEM to provide detailed information about evolution of oxide scale microstructure.

Direct imaging of charge transfer

1996 ◽  
Vol 54 ◽  
pp. 680-681
Author(s):  
Yimei Zhu ◽  
J. Tafto
Keyword(s):  
Charge Transfer ◽  
Electron Diffraction ◽  
Scattering Amplitude ◽  
High Temperature Superconductors ◽  
Charge Carriers ◽  
Image Charge ◽  
Net Charge ◽  
Long Time ◽  
Electron Holes ◽  
First Time

The electron holes confined to the CuO2-plane are the charge carriers in high-temperature superconductors, and thus, the distribution of charge plays a key role in determining their superconducting properties. While it has been known for a long time that in principle, electron diffraction at low angles is very sensitive to charge transfer, we, for the first time, show that under a proper TEM imaging condition, it is possible to directly image charge in crystals with a large unit cell. We apply this new way of studying charge distribution to the technologically important Bi2Sr2Ca1Cu2O8+δ superconductors.Charged particles interact with the electrostatic potential, and thus, for small scattering angles, the incident particle sees a nuclei that is screened by the electron cloud. Hence, the scattering amplitude mainly is determined by the net charge of the ion. Comparing with the high Z neutral Bi atom, we note that the scattering amplitude of the hole or an electron is larger at small scattering angles. This is in stark contrast to the displacements which contribute negligibly to the electron diffraction pattern at small angles because of the short g-vectors.

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