scholarly journals Metalloradical activation of α-formyldiazoacetates for the catalytic asymmetric radical cyclopropanation of alkenes

2017 ◽  
Vol 8 (6) ◽  
pp. 4347-4351 ◽  
Author(s):  
Xue Xu ◽  
Yong Wang ◽  
Xin Cui ◽  
Lukasz Wojtas ◽  
X. Peter Zhang
Keyword(s):  
Catalytic Asymmetric ◽  
First Time

For the first time, α-formyldiazoacetates (FDA), have been successfully applied for asymmetric olefin cyclopropanationviaCo(ii)-based metalloradical catalysis.

Catalytic asymmetric [2+2] cycloaddition between quinones and fulvenes and a subsequent stereoselective isomerization to 2,3-dihydrobenzofurans

2017 ◽  
Vol 53 (49) ◽  
pp. 6585-6588 ◽  
Author(s):  
Haifeng Zheng ◽  
Chaoran Xu ◽  
Yan Wang ◽  
Tengfei Kang ◽  
Xiaohua Liu ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Chiral Lewis Acid ◽  
Acid Catalyzed ◽  
Catalytic Asymmetric ◽  
First Time ◽  
Cyclobutane Derivatives

A chiral Lewis acid catalyzed enantioselective [2+2] cycloaddition between quinones and fulvenes was reported for the first time. The method afforded a series of [6,4,5]-tricyclic cyclobutane derivatives in good yields with excellent regio- and stereoselectivities. Furthermore, the [2+2] adducts could be easily converted into formal [3+2] adducts efficiently and stereoselectively.

Catalytic asymmetric Meerwein–Ponndorf–Verley reduction of glyoxylates induced by a chiral N,N′-dioxide/Y(OTf)3complex

2017 ◽  
Vol 53 (22) ◽  
pp. 3232-3235 ◽  
Author(s):  
Wangbin Wu ◽  
Sijia Zou ◽  
Lili Lin ◽  
Jie Ji ◽  
Yuheng Zhang ◽  
...  
Keyword(s):  
Catalytic Asymmetric ◽  
First Time ◽  
Mpv Reduction ◽  
Mechanism Of The Reaction

An asymmetric MPV reduction of glyoxylates was for the first time achieved with excellent results and the mechanism of the reaction was probed.

Catalytic asymmetric oxidative carbonylation-induced kinetic resolution of sterically hindered benzylamines to chiral isoindolinones

2021 ◽  
Vol 57 (14) ◽  
pp. 1778-1781
Author(s):  
Qiu-Qi Mu ◽  
Yi-Xue Nie ◽  
Hang Li ◽  
Xing-Feng Bai ◽  
Xue-Wei Liu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Kinetic Resolution ◽  
Oxidative Carbonylation ◽  
Sterically Hindered ◽  
Transition Metal Catalyzed ◽  
Catalytic Asymmetric ◽  
Metal Catalyzed ◽  
First Time

A highly enantioselective kinetic resolution of sterically hindered benzylamines has been achieved for the first time through transition-metal-catalyzed oxidative carbonylation.

Catalytic asymmetric dearomative [4+2] annulation of 2-nitrobenzofurans and 5H-thiazol-4-ones: stereoselective construction of dihydrobenzofuran-bridged polycyclic skeletons

2021 ◽  
Author(s):  
Jian-Qiang Zhao ◽  
Shun Zhou ◽  
Zhen-Hua Wang ◽  
Yong You ◽  
Shuang Chen ◽  
...  
Keyword(s):  
Polycyclic Compounds ◽  
Catalytic Asymmetric ◽  
First Time

An organocatalytic asymmetric dearomative [4+2] annulation of 2-nitrobenzofurans and 5H-thiazol-4-ones is described for the first time. With a chiral dipeptide-based squaramide as the catalyst, a series of dihydrobenzofuran-bridged polycyclic compounds...

scholarly journals Organocatalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones with bifunctional amine-thiourea catalysts bearing multiple hydrogen-bond donors

2016 ◽  
Vol 12 ◽  
pp. 295-300 ◽  
Author(s):  
Ming-Liang Zhang ◽  
Deng-Feng Yue ◽  
Zhen-Hua Wang ◽  
Yuan Luo ◽  
Xiao-Ying Xu ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Henry Reaction ◽  
Multiple Hydrogen Bond ◽  
Catalytic Asymmetric ◽  
Quaternary Stereocenters ◽  
First Time ◽  
Hydrogen Bond Donors

For the first time, a catalytic asymmetric Henry reaction of 1H-pyrrole-2,3-diones was achieved with a chiral bifunctional amine-thiourea as a catalyst possessing multiple hydrogen-bond donors. With this developed method, a range of 3-hydroxy-3-nitromethyl-1H-pyrrol-2(3H)-ones bearing quaternary stereocenters were obtained in acceptable yield (up to 75%) and enantioselectivity (up to 73% ee).

scholarly journals Synthesis of chiral sulfoximine-based thioureas and their application in asymmetric organocatalysis

2012 ◽  
Vol 8 ◽  
pp. 1443-1451 ◽  
Author(s):  
Marcus Frings ◽  
Isabelle Thomé ◽  
Carsten Bolm
Keyword(s):  
Biginelli Reaction ◽  
Core Fragment ◽  
Asymmetric Organocatalysis ◽  
Synthetic Routes ◽  
Catalytic Asymmetric ◽  
First Time ◽  
Sulfur Containing

For the first time, chiral sulfoximine derivatives have been applied as asymmetric organocatalysts. In combination with a thiourea-type backbone the sulfonimidoyl moiety leads to organocatalysts showing good reactivity in the catalytic desymmetrization of a cyclic meso-anhydride and moderate enantioselectivity in the catalytic asymmetric Biginelli reaction. Straightforward synthetic routes provide the newly designed thiourea-sulfoximine catalysts in high overall yields without affecting the stereohomogeneity of the sulfur-containing core fragment.

Catalytic asymmetric (4 + 1) annulation of nitroalkenes with allylic acetates: stereoselective synthesis of isoxazoline N-oxides

2019 ◽  
Vol 17 (29) ◽  
pp. 6989-6993 ◽  
Author(s):  
Jinghua Luo ◽  
Rongshun Chen ◽  
Xia Fan ◽  
Junyu Gong ◽  
Jie Han ◽  
...  
Keyword(s):  
Stereoselective Synthesis ◽  
Catalytic Asymmetric ◽  
First Time

A highly enantioselective catalytic asymmetric (4 + 1) annulation reaction of nitroalkenes and ammonium ylides is reported for the first time.

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.

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