Rhodium(II) Metallopeptide Catalyst Design Enables Fine Control in Selective Functionalization of Natural SH3 Domains

2015 ◽  
Vol 127 (15) ◽  
pp. 4670-4674 ◽  
Author(s):  
Farrukh Vohidov ◽  
Jane M. Coughlin ◽  
Zachary T. Ball
Keyword(s):  
Catalyst Design ◽  
Sh3 Domains ◽  
Selective Functionalization ◽  
Fine Control

scholarly journals CO2-Mediated Pd-Catalyzed Stereo- and Regioselective Arylation of Free Allylamines

2020 ◽  
Author(s):  
Vinod Landge ◽  
Justin Maxwell ◽  
Pratibha Chand-Thakuri ◽  
Mohit Kapoor ◽  
Evan Diemler ◽  
...  
Keyword(s):  
Catalyst Design ◽  
Powerful Method ◽  
Mechanistic Studies ◽  
Atom Economy ◽  
Biologically Relevant ◽  
Mild Conditions ◽  
Selective Functionalization ◽  
Michael Acceptors ◽  
Key Features ◽  
Terminal Olefins

Mizoroki-Heck couplings are a powerful method for elaborating alkene feedstocks. While selective functionalization of terminal olefins has been achieved by catalyst design, selective functionalization of internal olefins has generally required use of directing groups except in the case of Michael acceptors. Allylamine substrates have typically required protection to be suitable for these reactions, decreasing the step and atom economy of these procedures. Herein we demonstrate that the addition of CO<sub>2</sub> (dry ice) allows for the reproducible stereospecific arylation of both secondary and primary allylamines in the presence of a Pd<sup>II</sup> catalyst. Notably, the product 3,3’-diarylallylamine motif is prevalent in a variety of biologically-relevant structures, and this method represents the most straightforward synthesis of these targets to date. Key features of the method are the ability to access relatively mild conditions that facilitate a broad substrate scope, as well as direct diarylation of terminal allylamine substrates. In addition, several complex and therapeutically-relevant molecules are included to demonstrate the utility of the transformation. Mechanistic studies point to an amine-directed reaction where CO<sub>2</sub> serves to protect the substrate and product from degradation.

scholarly journals CO2-Mediated Pd-Catalyzed Stereo- and Regioselective Arylation of Free Allylamines

2020 ◽  
Author(s):  
Vinod Landge ◽  
Justin Maxwell ◽  
Pratibha Chand-Thakuri ◽  
Mohit Kapoor ◽  
Evan Diemler ◽  
...  
Keyword(s):  
Catalyst Design ◽  
Powerful Method ◽  
Mechanistic Studies ◽  
Atom Economy ◽  
Biologically Relevant ◽  
Mild Conditions ◽  
Selective Functionalization ◽  
Michael Acceptors ◽  
Key Features ◽  
Terminal Olefins

Mizoroki-Heck couplings are a powerful method for elaborating alkene feedstocks. While selective functionalization of terminal olefins has been achieved by catalyst design, selective functionalization of internal olefins has generally required use of directing groups except in the case of Michael acceptors. Allylamine substrates have typically required protection to be suitable for these reactions, decreasing the step and atom economy of these procedures. Herein we demonstrate that the addition of CO2 (dry ice) allows for the reproducible stereospecific arylation of both secondary and primary allylamines in the presence of a PdII catalyst. Notably, the product 3,3’-diarylallylamine motif is prevalent in a variety of biologically-relevant structures, and this method represents the most straightforward synthesis of these targets to date. Key features of the method are the ability to access relatively mild conditions that facilitate a broad substrate scope, as well as direct diarylation of terminal allylamine substrates. In addition, several complex and therapeutically-relevant molecules are included to demonstrate the utility of the transformation. Mechanistic studies point to an amine-directed reaction where CO2 serves to protect the substrate and product from degradation.

scholarly journals CO2 As A Transient Directing Group for the Oxidative Heck Coupling of Free Allylamines With Aryl Iodides

2020 ◽  
Author(s):  
Vinod Landge ◽  
Justin Maxwell ◽  
Pratibha Chand-Thakuri ◽  
Mohit Kapoor ◽  
Evan Diemler ◽  
...  
Keyword(s):  
Catalyst Design ◽  
Heck Coupling ◽  
Powerful Method ◽  
Atom Economy ◽  
Biologically Relevant ◽  
Mild Conditions ◽  
Selective Functionalization ◽  
Michael Acceptors ◽  
Directing Group ◽  
Terminal Olefins

Oxidative Heck couplings are a powerful method for elaborating alkene feedstocks. While selective functionalization of terminal olefins has been achieved by catalyst design, selective functionalization of internal olefins has generally required use of directing groups except in the case of Michael acceptors. Allylamine substrates have typically required protection to be suitable for these reactions, decreasing the step and atom economy of these procedures. Herein we demonstrate that the addition of CO<sub>2</sub> (dry ice) as a transient directing group allows for the stereospecific arylation of both secondary and primary allylamines in the presence of a Pd<sup>II</sup> catalyst. Notably, the product 3,3’-diarylallylamine motif is prevalent in a variety of biologically-relevant structures, and this method represents the most straightforward synthesis of these targets to date. Key features of the method are the ability to access relatively mild conditions that facilitate a broad substrate scope, as well as direct diarylation of terminal allylamine substrates. In addition, several complex and therapeutically-relevant molecules are included to demonstrate the utility of the transformation.

Arene diversification through distal C(sp2)−H functionalization

Science ◽  
2021 ◽  
Vol 372 (6543) ◽  
pp. eabd5992
Author(s):  
Uttam Dutta ◽  
Sudip Maiti ◽  
Trisha Bhattacharya ◽  
Debabrata Maiti
Keyword(s):  
Transition Metal ◽  
Noncovalent Interactions ◽  
Catalyst Design ◽  
Selective Functionalization ◽  
Directing Group ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed ◽  
Site Selective

Transition metal–catalyzed aryl C−H activation is a powerful synthetic tool as it offers step and atom-economical routes to site-selective functionalization. Compared with proximal ortho-C−H activation, distal (meta- and/or para-) C−H activation remains more challenging due to the inaccessibility of these sites in the formation of energetically favorable organometallic pretransition states. Directing the catalyst toward the distal C−H bonds requires judicious template engineering and catalyst design, as well as prudent choice of ligands. This review aims to summarize the recent elegant discoveries exploiting directing group assistance, transient mediators or traceless directors, noncovalent interactions, and catalyst and/or ligand selection to control distal C−H activation.

Novel Coupling Agents for Silica-filled Rubbers with Superior Processing Safety and Improved Hysteresis of the Vulcanizates

2010 ◽  
Vol 38 (1) ◽  
pp. 80-98 ◽  
Author(s):  
M. Gerster ◽  
C. Fagouri ◽  
E. Peregi
Keyword(s):  
Mixing Time ◽  
Cost Savings ◽  
Coupling Agents ◽  
Tire Industry ◽  
Selective Functionalization ◽  
Current State ◽  
Rubber Compounds ◽  
Volatile Organic ◽  
Filled Rubbers ◽  
Ethanol Removal

Abstract One challenge facing green tire technology is to achieve good silica hydrophobation/dispersion within the polymer matrix without a detrimental increase in the rubber compound’s viscosity during compounding. This phenomenon is well known to be induced by premature and unwanted coupling and/or crosslinking of the traditional coupling agents. The current state-of-the-art polysulfides silanes, bis(3-triethoxysilylpropyl)tetrasulfide and to a lesser extent bis(3-triethoxysilylpropyl)disulfide (“Product Application—VP Si 75/VP X 75-S in the Rubber Industry,” Degussa Hüls Report No. PA 723.1E), need to be carefully incorporated with careful temperature control during the rubber compounding to prevent this “scorchy” behavior. This paper will present novel monofunctional silanes which are suited for preparing highly silica-loaded rubber compounds of superior processability, while applying fewer mixing passes, thereby reducing mixing times which can lead to improved productivity and cost savings. Additionally, these safer coupling agents can be processed at higher temperatures which can, again, lead to reduced mixing time and better ethanol removal thereby improving the tire’s physical properties and reducing the volatile organic compounds generated during the tire’s use. The rubber compounds produced using these monofunctional silanes are characterized by lower Mooney viscosity and improved processability. Advantageously, within these novel chemical classes of coupling agents, selective functionalization of the silanes allows production of tailor-made coupling agents which can respond to the specific requirements of the tire industry (Vilgis, T. A. and Heinrich, G., “Die Physic des Autoreifens,” Physikalische Blätter, Vol. 57, 2001, pp. 1–7).

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

Iterative Supervised Principal Component Analysis-Driven Ligand Design for Regioselective Ti-Catalyzed Pyrrole Synthesis

2020 ◽  
Author(s):  
Xin Yi See ◽  
Benjamin Reiner ◽  
Xuelan Wen ◽  
T. Alexander Wheeler ◽  
Channing Klein ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
De Novo ◽  
Principal Component ◽  
Component Analysis ◽  
Catalyst Design ◽  
Data Driven ◽  
Initial Reaction ◽  
Training Set ◽  
Reaction Conditions ◽  
Component Loadings

<div> <div> <div> <p>Herein, we describe the use of iterative supervised principal component analysis (ISPCA) in de novo catalyst design. The regioselective synthesis of 2,5-dimethyl-1,3,4-triphenyl-1H- pyrrole (C) via Ti- catalyzed formal [2+2+1] cycloaddition of phenyl propyne and azobenzene was targeted as a proof of principle. The initial reaction conditions led to an unselective mixture of all possible pyrrole regioisomers. ISPCA was conducted on a training set of catalysts, and their performance was regressed against the scores from the top three principal components. Component loadings from this PCA space along with k-means clustering were used to inform the design of new test catalysts. The selectivity of a prospective test set was predicted in silico using the ISPCA model, and only optimal candidates were synthesized and tested experimentally. This data-driven predictive-modeling workflow was iterated, and after only three generations the catalytic selectivity was improved from 0.5 (statistical mixture of products) to over 11 (> 90% C) by incorporating 2,6-dimethyl- 4-(pyrrolidin-1-yl)pyridine as a ligand. The successful development of a highly selective catalyst without resorting to long, stochastic screening processes demonstrates the inherent power of ISPCA in de novo catalyst design and should motivate the general use of ISPCA in reaction development. </p> </div> </div> </div>

Selective Functionalization at N2-Position of Guanine in Oligonucleotides via Reductive Amination

2020 ◽  
Author(s):  
Bapurao Bhoge ◽  
Ishu Saraogi
Keyword(s):  
Organic Chemistry ◽  
Chemical Biology ◽  
Reductive Amination ◽  
The Other ◽  
Dna Oligomers ◽  
Site Specific ◽  
Wide Applicability ◽  
Dna Oligonucleotides ◽  
Selective Functionalization

Chemo- and site-specific modifications in oligonucleotides have wide applicability as mechanistic probes in chemical biology. Here we have employed a classical reaction in organic chemistry, reductive amination, to selectively functionalize the N<sup>2</sup>-amine of guanine/2’-deoxyguanine monophosphate. This method specifically modifies guanine in several tested DNA oligonucleotides, while leaving the other bases unaffected. Using this approach, we have successfully incorporated desired handles chemoselectively into DNA oligomers.

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