scholarly journals Enantioselective Hydroalkylation of α,β-Unsaturated Amides through Reversed syn-Hydrometallation of NiH

2021 ◽  
Author(s):  
Fang Zhou ◽  
Shaolin Zhu
Keyword(s):  
Enantioselective Synthesis ◽  
Recombination Process ◽  
Chiral Induction ◽  
Wide Range ◽  
Alkyl Iodides

Enantioselective synthesis of a wide range of structurally diverse <a>β</a>-chiral amides has been achieved through nickel-catalyzed regio-reversed hydroalkylation of α,β-unsaturated amides with alkyl iodides in the presence of a hydrosilane. Different from the classical homolysis/enantioconvergent recombination process of Ni(III) intermediates as the enantio-determining step, chiral induction in this reductive hydroalkylation was achieved through an enantiodifferentiating regio-reversed <i>syn</i>-hydrometallation process of α,β-unsaturated amides.

scholarly journals Enantioselective Hydroalkylation of α,β-Unsaturated Amides through Reversed syn-Hydrometallation of NiH

2021 ◽  
Author(s):  
Fang Zhou ◽  
Shaolin Zhu
Keyword(s):  
Enantioselective Synthesis ◽  
Recombination Process ◽  
Chiral Induction ◽  
Wide Range ◽  
Alkyl Iodides

Enantioselective synthesis of a wide range of structurally diverse <a>β</a>-chiral amides has been achieved through nickel-catalyzed regio-reversed hydroalkylation of α,β-unsaturated amides with alkyl iodides in the presence of a hydrosilane. Different from the classical homolysis/enantioconvergent recombination process of Ni(III) intermediates as the enantio-determining step, chiral induction in this reductive hydroalkylation was achieved through an enantiodifferentiating regio-reversed <i>syn</i>-hydrometallation process of α,β-unsaturated amides.

1,3-Diethynylallenes (DEAs): Enantioselective Synthesis, Absolute Configuration, and Chiral Induction in 1,1,4,4-Tetracyanobuta-1,3-dienes (TCBDs)

2008 ◽  
Vol 14 (34) ◽  
pp. 10564-10568 ◽  
Author(s):  
José Lorenzo Alonso-Gómez ◽  
Patrick Schanen ◽  
Pablo Rivera-Fuentes ◽  
Paul Seiler ◽  
François Diederich
Keyword(s):  
Absolute Configuration ◽  
Enantioselective Synthesis ◽  
Chiral Induction

scholarly journals Biomimetic enantioselective synthesis of β,β-difluoro-α-amino acid derivatives

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Qiupeng Peng ◽  
Bingjia Yan ◽  
Fangyi Li ◽  
Ming Lang ◽  
Bei Zhang ◽  
...  
Keyword(s):  
Amino Acid ◽  
Structural Diversity ◽  
Enantioselective Synthesis ◽  
Amino Acid Derivatives ◽  
Proton Shift ◽  
Wide Range ◽  
Fluorine Compounds ◽  
Optically Pure ◽  
High Stereoselectivity ◽  
High Application

AbstractAlthough utilization of fluorine compounds has a long history, synthesis of chiral fluorinated amino acid derivatives with structural diversity and high stereoselectivity is still very appealing and challenging. Here, we report a biomimetic study of enantioselective [1,3]-proton shift of β,β-difluoro-α-imine amides catalyzed by chiral quinine derivatives. A wide range of corresponding β,β-difluoro-α-amino amides were achieved in good yields with high enantioselectivities. The optically pure β,β-difluoro-α-amino acid derivatives were further obtained, which have high application values in the synthesis of fluoro peptides, fluoro amino alcohols and other valuable fluorine-containing molecules.

scholarly journals Chiral Alkyl Amine Synthesis via Catalytic Enantioselective Hydroalkylation of Enamides

2020 ◽  
Author(s):  
Deyun Qian ◽  
Srikrishna Bera ◽  
Xile Hu
Keyword(s):  
Natural Products ◽  
Functional Group ◽  
Building Blocks ◽  
Alkyl Halides ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Drug Molecules ◽  
Alkyl Amines ◽  
Wide Range ◽  
Synthetic Intermediates

Chiral alkyl amines are omnipresent as bio-active molecules and synthetic intermediates. Catalytic and enantioselective synthesis of alkyl amines from readily accessible precursors is challenging. Here we develop a nickel-catalyzed hydroalkylation method to assemble a wide range of chiral alkyl amines from enamides and alkyl halides in high regio- and enantioselectivity. The method works for both non-activated and activated alkyl halides, and is able to produce enantiomerically enriched amines with two minimally differentiated alpha-alkyl substituents. The mild conditions lead to high functional group tolerance, which is demonstrated in the post-product functionalization of many natural products and drug molecules, as well as the synthesis of chiral building blocks and key intermediates to bio-active compounds.

scholarly journals Chiral Alkyl Amine Synthesis via Catalytic Enantioselective Hydroalkylation of Enamides

2020 ◽  
Author(s):  
Deyun Qian ◽  
Srikrishna Bera ◽  
Xile Hu
Keyword(s):  
Natural Products ◽  
Functional Group ◽  
Building Blocks ◽  
Alkyl Halides ◽  
Enantioselective Synthesis ◽  
Mild Conditions ◽  
Drug Molecules ◽  
Alkyl Amines ◽  
Wide Range ◽  
Synthetic Intermediates

Chiral alkyl amines are omnipresent as bio-active molecules and synthetic intermediates. Catalytic and enantioselective synthesis of alkyl amines from readily accessible precursors is challenging. Here we develop a nickel-catalyzed hydroalkylation method to assemble a wide range of chiral alkyl amines from enamides and alkyl halides in high regio- and enantioselectivity. The method works for both non-activated and activated alkyl halides, and is able to produce enantiomerically enriched amines with two minimally differentiated alpha-alkyl substituents. The mild conditions lead to high functional group tolerance, which is demonstrated in the post-product functionalization of many natural products and drug molecules, as well as the synthesis of chiral building blocks and key intermediates to bio-active compounds.

scholarly journals Direct Access to Highly Enantioenriched α-Branched Acrylonitriles through a one-pot Sequential Asymmetric Michael addition/retro-Dieckmann/retro-Michael Fragmentation Cascade

2020 ◽  
Author(s):  
Nicolas Duchemin ◽  
Martin Cattoen ◽  
Oscar Gayraud ◽  
Silvia Anselmi ◽  
Bilal Siddiq ◽  
...  
Keyword(s):  
Michael Addition ◽  
Building Blocks ◽  
Enantioselective Synthesis ◽  
Direct Access ◽  
One Pot ◽  
Asymmetric Michael Addition ◽  
Wide Range

A highly enantioselective synthesis of a-branched acrylonitriles is reported featuring a one-pot sequential asymmetric Michael addition/retro-Dieckmann/retro-Michael fragmentation cascade. The method, which relies on a solid, bench-stable and commercially available acrylonitrile surrogate, is practical, scalable, highly versatile, and provides a direct access to a wide range of enantioenriched nitrile-containing building blocks. Most importantly, the method offers a new tool to incorporate an acrylonitrile moiety in an asymmetric fashion.<br>

scholarly journals Direct Access to Highly Enantioenriched α-Branched Acrylonitriles through a Formal Cross Rauhut-Currier Reaction

2020 ◽  
Author(s):  
Nicolas Duchemin ◽  
Martin Cattoen ◽  
Oscar Gayraud ◽  
Silvia Anselmi ◽  
Bilal Siddiq ◽  
...  
Keyword(s):  
Michael Addition ◽  
Building Blocks ◽  
Enantioselective Synthesis ◽  
Direct Access ◽  
Asymmetric Michael Addition ◽  
Wide Range

A highly enantioselective synthesis of α-branched acrylonitriles is reported featuring an unprecedented formal cross Rauhut-Currier reaction consisting of an asymmetric Michael addition/retro-Dieckmann/retro-Michael fragmentation cascade. The method, which involves the use of an acrylonitrile surrogate, is practical, scalable and highly versatile, and provides a straightforward access to a wide range of enantioenriched nitrile-containing building blocks without using acrylonitrile or any source of cyanide. Most importantly, it offers a new tool to incorporate an acrylonitrile moiety in an asymmetric fashion.<br>

Enantioselective Synthesis of Optically Active O -Benzoyl-Protected α-Hydroxyl-β,γ-Unsaturated Acids with Chiral Induction of (S )-Glyceraldehyde Acetonide

2017 ◽  
Vol 2 (34) ◽  
pp. 11240-11243
Author(s):  
Ruiquan Liu ◽  
Lei Wang ◽  
Qibo Li ◽  
Min Liao ◽  
Zhikun Yang ◽  
...  
Keyword(s):  
Optically Active ◽  
Enantioselective Synthesis ◽  
Chiral Induction

Recent Applications of High Resolution Electron Microscopy to Crystalline Arrays of Virus Particles

1978 ◽  
Vol 36 (3) ◽  
pp. 470-482 ◽  
Author(s):  
R.W. Horne
Keyword(s):  
Electron Microscopy ◽  
Image Processing ◽  
Analytical Techniques ◽  
Staining Technique ◽  
High Resolution Electron Microscopy ◽  
Optical Diffraction ◽  
Full Potential ◽  
Virus Particles ◽  
Resolution Electron ◽  
Wide Range

The technique of surrounding virus particles with a neutralised electron dense stain was described at the Fourth International Congress on Electron Microscopy, Berlin 1958 (see Home & Brenner, 1960, p. 625). For many years the negative staining technique in one form or another, has been applied to a wide range of biological materials. However, the full potential of the method has only recently been explored following the development and applications of optical diffraction and computer image analytical techniques to electron micrographs (cf. De Hosier & Klug, 1968; Markham 1968; Crowther et al., 1970; Home & Markham, 1973; Klug & Berger, 1974; Crowther & Klug, 1975). These image processing procedures have allowed a more precise and quantitative approach to be made concerning the interpretation, measurement and reconstruction of repeating features in certain biological systems.

Microfabrication research at the National Submicron Facility

1983 ◽  
Vol 41 ◽  
pp. 86-89
Author(s):  
E.D. Wolf
Keyword(s):  
Integrated Circuits ◽  
Particle Physics ◽  
High Speed ◽  
New Technology ◽  
High Energy ◽  
High Energy Particle ◽  
New Science ◽  
Wide Range ◽  
Intermediate Domain ◽  
Circuit Function

Most microelectronics devices and circuits operate faster, consume less power, execute more functions and cost less per circuit function when the feature-sizes internal to the devices and circuits are made smaller. This is part of the stimulus for the Very High-Speed Integrated Circuits (VHSIC) program. There is also a need for smaller, more sensitive sensors in a wide range of disciplines that includes electrochemistry, neurophysiology and ultra-high pressure solid state research. There is often fundamental new science (and sometimes new technology) to be revealed (and used) when a basic parameter such as size is extended to new dimensions, as is evident at the two extremes of smallness and largeness, high energy particle physics and cosmology, respectively. However, there is also a very important intermediate domain of size that spans from the diameter of a small cluster of atoms up to near one micrometer which may also have just as profound effects on society as “big” physics.

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