A Sequential Process of Graphene Exfoliation and Site-Selective Copper/Graphene Metallization Enabled by Multifunctional 1-Pyrenebutyric Acid Tetrabutylammonium Salt

2019 ◽  
Vol 11 (6) ◽  
pp. 6448-6455 ◽  
Author(s):  
Jie Zhao ◽  
Chenyu Wen ◽  
Rui Sun ◽  
Shi-Li Zhang ◽  
Biao Wu ◽  
...  
Keyword(s):  
Sequential Process ◽  
Tetrabutylammonium Salt ◽  
Site Selective

Chemical and Electrochemical Heteroepitaxial Growth of Chalcogenide Semiconductors from Solutions

1996 ◽  
Vol 451 ◽  
Author(s):  
D. Lincot ◽  
M. J. Furlong ◽  
M. Froment ◽  
R. Cortes ◽  
M. C. Bernard
Keyword(s):  
Heteroepitaxial Growth ◽  
X Ray Diffraction ◽  
Basic Principles ◽  
Lattice Match ◽  
X Ray ◽  
Chalcogenide Semiconductors ◽  
Influence Of Temperature On ◽  
Deposition Processes ◽  
A Site ◽  
Site Selective

ABSTRACTChalcogenide semiconductors have been deposited epitaxially from aqueous solutions either chemically or electrochemically at growth rates of up to 0.7 μmhr−1. After recalling the basic principles of these deposition processes, results are presented concerning chemically deposited CdS on InP, GaP and CuInSe2 substrates, electrodeposited CdTe on InP, and CdSAnP heterostructures. Characterisation of these structures by RHEED, TEM, HRTEM, and glazing angle X ray diffraction allows to analyse the effects of substrate orientation, polarity, lattice match plus the influence of temperature on epitaxial growth. These results are discussed in terms of self organisation and a site selective growth mechanisms due to the free enegy of formation of each compound.

para-Selective Cyanation of Arenes by H-Bonded Template

2019 ◽  
Author(s):  
Sandeep Pimparkar ◽  
Trisha Bhattacharya ◽  
Arun Maji ◽  
Argha Saha ◽  
Ramasamy Jayarajan ◽  
...  
Keyword(s):  
Selective Functionalization ◽  
Directing Group ◽  
Product Utility ◽  
Site Selective

The significance of site selective functionalization stands upon the superior selectivity, easy synthesis and diverse product utility. In this work we demonstrate the <i>para</i>-selective introduction of versatile nitrile moiety, enabled by detachable and reusable H-bonded auxiliary. The methodology holds its efficiency irrespective of substrate electronic bias. The conspicuous shift in the step energetics was probed by both experimental and computational mechanistic tools heralds the inception of <i>para</i>-deuteration. The synthetic impact of the methodology was highlighted with reusability of directing group and post synthetic modifications

para-Selective Cyanation of Arenes by H-Bonded Template

2019 ◽  
Author(s):  
Sandeep Pimparkar ◽  
Trisha Bhattacharya ◽  
Arun Maji ◽  
Argha Saha ◽  
Ramasamy Jayarajan ◽  
...  
Keyword(s):  
Selective Functionalization ◽  
Directing Group ◽  
Product Utility ◽  
Site Selective

The significance of site selective functionalization stands upon the superior selectivity, easy synthesis and diverse product utility. In this work we demonstrate the <i>para</i>-selective introduction of versatile nitrile moiety, enabled by detachable and reusable H-bonded auxiliary. The methodology holds its efficiency irrespective of substrate electronic bias. The conspicuous shift in the step energetics was probed by both experimental and computational mechanistic tools heralds the inception of <i>para</i>-deuteration. The synthetic impact of the methodology was highlighted with reusability of directing group and post synthetic modifications

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

2020 ◽  
Author(s):  
Chang-Sheng Wang ◽  
Sabrina Monaco ◽  
Anh Ngoc Thai ◽  
Md. Shafiqur Rahman ◽  
Chen Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Hydrogen Transfer ◽  
Acid Catalysis ◽  
Rate Limiting Step ◽  
Site Selectivity ◽  
Set Up ◽  
Site Selective ◽  
First Time ◽  
Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

Systematic Engineering of a Protein Nanocage for High-Yield, Site-Specific Modification

2018 ◽  
Author(s):  
Daniel D. Brauer ◽  
Emily C. Hartman ◽  
Daniel L.V. Bader ◽  
Zoe N. Merz ◽  
Danielle Tullman-Ercek ◽  
...  
Keyword(s):  
Small Molecules ◽  
Protein Modification ◽  
Positive Charge ◽  
Specific Protein ◽  
High Yield ◽  
Site Specific ◽  
Protein Cage ◽  
Protein Carriers ◽  
Site Selective ◽  
Targeted Library

<div> <p>Site-specific protein modification is a widely-used strategy to attach drugs, imaging agents, or other useful small molecules to protein carriers. N-terminal modification is particularly useful as a high-yielding, site-selective modification strategy that can be compatible with a wide array of proteins. However, this modification strategy is incompatible with proteins with buried or sterically-hindered N termini, such as virus-like particles like the well-studied MS2 bacteriophage coat protein. To assess VLPs with improved compatibility with these techniques, we generated a targeted library based on the MS2-derived protein cage with N-terminal proline residues followed by three variable positions. We subjected the library to assembly, heat, and chemical selections, and we identified variants that were modified in high yield with no reduction in thermostability. Positive charge adjacent to the native N terminus is surprisingly beneficial for successful extension, and over 50% of the highest performing variants contained positive charge at this position. Taken together, these studies described nonintuitive design rules governing N-terminal extensions and identified successful extensions with high modification potential.</p> </div>

Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

2017 ◽  
Author(s):  
Haibo Ge ◽  
Lei Pan ◽  
Piaoping Tang ◽  
Ke Yang ◽  
Mian Wang ◽  
...  
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Bond Functionalization ◽  
Aliphatic Ketones ◽  
Site Selectivity ◽  
Mechanistic Investigation ◽  
Palladium Catalyzed ◽  
Metal Catalyzed ◽  
Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp<sup>3</sup> carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp<sup>3</sup>)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp<sup>3</sup>)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.<br><br>

Differentiation and Functionalization of Adjacent, Remote C–H Bonds

2019 ◽  
Author(s):  
Hang Shi ◽  
Lu Yi ◽  
Jiang Weng ◽  
Katherine Bay ◽  
Xiangyang Chen ◽  
...  
Keyword(s):  
Catalytic System ◽  
Functional Group ◽  
Hydrocinnamic Acid ◽  
Molecular Architectures ◽  
Site Selective ◽  
Developing Strategies

<p>Site-selective functionalizations of C–H bonds will ultimately afford chemists transformative tools for editing and constructing complex molecular architectures<sup>1-4</sup>. Towards this goal, developing strategies to activate C–H bonds that are distal from a functional group is essential<sup>4-6</sup>. In this context, distinguishing remote C–H bonds on adjacent carbon atoms is an extraordinary challenge due to the lack of electronic or steric bias between the two positions. Herein, we report the design of a catalytic system leveraging a remote directing template and a transient norbornene mediator to selectively activate a previously inaccessible remote C–H bond that is one bond further away. The generality of this approach has been demonstrated with a range of heterocycles, including a complex anti-leukemia agent, and hydrocinnamic acid substrates.</p>

Synthesis of Conjugated Triynes via Alkyne Metathesis

2019 ◽  
Author(s):  
Idriss Curbet ◽  
Sophie Colombel-Rouen ◽  
Romane Manguin ◽  
Anthony Clermont ◽  
Alexandre Quelhas ◽  
...  
Keyword(s):  
Steric Hindrance ◽  
High Selectivity ◽  
Alkyne Metathesis ◽  
Cross Metathesis ◽  
Synthetic Strategy ◽  
Sterically Hindered ◽  
Site Selective

<div> <div> <div> <div> <p>The synthesis of conjugated triynes by molybdenum-catalyzed alkyne metathesis is reported. Strategic to the success of this approach is the utilization of sterically-hindered diynes that allowed for the site- selective alkyne metathesis to produce the desired con- jugated triyne products. The steric hindrance of alkyne moiety was found to be crucial in preventing the for- mation of diyne byproducts. This novel synthetic strategy was amenable to self- and cross-metathesis providing straightforward access to the corresponding symmetrical and dissymmetrical triynes with high selectivity. </p> </div> </div> </div> </div>

Sign in / Sign up

Export Citation Format

Share Document