N-Tosylhydrazone directed annulation via C–H/N–N bond activation in Ru(ii)/PEG-400 as homogeneous recyclable catalytic system: a green synthesis of isoquinolines

2018 ◽  
Vol 16 (26) ◽  
pp. 4864-4873 ◽  
Author(s):  
Dewal S. Deshmukh ◽  
Bhalchandra M. Bhanage
Keyword(s):  
Green Synthesis ◽  
Catalytic System ◽  
Bond Activation ◽  
Peg 400 ◽  
System A ◽  
Directing Group

A green and sustainable methodology for the synthesis of isoquinolines using Ru(ii)/PEG-400 as homogeneous recyclable catalytic system and N-tosylhydrazone, a rarely explored directing group has been reported.

scholarly journals Combination of RuCl3·xH2O with PEG – a simple and recyclable catalytic system for direct arylation of heteroarenes via C–H bond activation

RSC Advances ◽  
2017 ◽  
Vol 7 (38) ◽  
pp. 23515-23522 ◽  
Author(s):  
Lei Jian ◽  
Hai-Yu He ◽  
Jin Huang ◽  
Qian-Hui Wu ◽  
Mao-Lin Yuan ◽  
...  
Keyword(s):  
Catalytic System ◽  
Bond Activation ◽  
Direct Arylation ◽  
Peg 400

A simple and recyclable catalytic system for direct arylation of heteroarenes via C–H bond activation was developed with a relatively inexpensive RuCl3·xH2O as a catalyst and PEG-400 as a green medium without any additive or ligand.

Imine as a Linchpin Approach for Distal C(sp2)–H Functionalization

2020 ◽  
Author(s):  
Sukdev Bag ◽  
Sadhan Jana ◽  
Sukumar Pradhan ◽  
Suman Bhowmick ◽  
Nupur Goswami ◽  
...  
Keyword(s):  
Organic Molecules ◽  
Bond Activation ◽  
Bond Formation ◽  
Ancillary Ligand ◽  
Significant Challenge ◽  
Site Selectivity ◽  
Directing Group ◽  
Covalently Linked ◽  
Complex Organic ◽  
Post Functionalization

<p>Despite the widespread applications of C–H functionalization, controlling site selectivity remains a significant challenge. Covalently attached directing group (DG) served as an ancillary ligand to ensure proximal <i>ortho</i>-, distal <i>meta</i>- and <i>para</i>-C-H functionalization over the last two decades. These covalently linked DGs necessitate two extra steps for a single C–H functionalization: introduction of DG prior to C–H activation and removal of DG post-functionalization. We introduce here a transient directing group for distal C(<i>sp<sup>2</sup></i>)-H functionalization <i>via</i> reversible imine formation. By overruling facile proximal C-H bond activation by imine-<i>N</i> atom, a suitably designed pyrimidine-based transient directing group (TDG) successfully delivered selective distal C-C bond formation. Application of this transient directing group strategy for streamlining the synthesis of complex organic molecules without any necessary pre-functionalization at the distal position has been explored.</p>

scholarly journals Palladium-Catalysed C–F Alumination of Fluorobenzenes: Mechanistic Diversity and Origin of Selectivity

2020 ◽  
Author(s):  
Feriel Rekhroukh ◽  
Wenyi Chen ◽  
Ryan Brown ◽  
Andrew J. P. White ◽  
Mark Crimmin
Keyword(s):  
Dft Calculations ◽  
Bond Activation ◽  
Oxidative Addition ◽  
Fluorine Content ◽  
Model Potential ◽  
Heterometallic Complex ◽  
Experimental Support ◽  
Highly Active ◽  
Reaction Proceeds ◽  
Directing Group

A palladium pre-catalyst, [Pd(PCy<sub>3</sub>)<sub>2</sub>] is reported for the efficient and selective C–F alumination of fluorobenzenes with the aluminium(I) reagent [{(ArNCMe)<sub>2</sub>CH}Al] (<b>1</b>, Ar = 2,6-di-iso-propylphenyl). The catalytic protocol results in the transformation of sp<sup>2</sup> C–F bonds to sp<sup>2</sup> C–Al bonds and provides a route into reactive organoaluminium complexes (<b>2a-h</b>) from fluorocarbons. The catalyst is highly active. Reactions proceed within 5 minutes at 25 ºC (and at appreciable rates at even –50 ºC) and the scope includes low-fluorine-content substrates such as fluorobenzene, difluorobenzenes and trifluorobenzenes. The reaction proceeds with complete chemoselectivity (C–F vs C–H) and high regioselectivities ( >90% for C–F bonds adjacent to the most acidic C–H sites). The heterometallic complex [Pd(PCy<sub>3</sub>)(<b>1</b>)<sub>2</sub>] was shown to be catalytically competent. Catalytic C–F alumination proceeds with a KIE of 1.1–1.3. DFT calculations have been used to model potential mechanisms for C–F bond activation. These calculations suggest that two competing mechanisms may be in operation. Pathway 1 involves a ligand-assisted oxidative addition to [Pd(<b>1</b>)<sub>2</sub>] and leads directly to the product. Pathway 2 involves a stepwise C–H to C–F functionalisation mechanism in which the C–H bond is broken and reformed along the reaction coordinate, allowing it to act as a directing group for the adjacent C–F site. This second mechanism explains the experimentally observed regioselectivity. Experimental support for this C–H activation playing a key role in C–F alumination was obtained by employing [{(MesNCMe)<sub>2</sub>CH}AlH<sub>2</sub>] (<b>3</b>, Mes = 2,4,6-trimethylphenyl) as a reagent in place of 1. In this instance, the kinetic C–H alumination intermediate could be isolated. Under catalytic conditions this intermediate converts to the thermodynamic C–F alumination product.

Pd-Mediated γ-C(sp3)–H Bond Activation in Ammonia–Ugi 4-CR Adducts by Using Picolinamide as Directing Group

2019 ◽  
Vol 84 (20) ◽  
pp. 12809-12834 ◽  
Author(s):  
Diego Alemán-Ponce de León ◽  
Anahí C. Sánchez-Chávez ◽  
Luis A. Polindara-García
Keyword(s):  
Bond Activation ◽  
Directing Group

Solvent-free oxidative cleavage of epoxy fatty acid methyl esters by a “release and capture” catalytic system

2019 ◽  
Vol 21 (3) ◽  
pp. 560-566 ◽  
Author(s):  
Meizhen Lu ◽  
Libo Peng ◽  
Qinglong Xie ◽  
Ni Yang ◽  
Hailun Jin ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Green Synthesis ◽  
Catalytic System ◽  
Vegetable Oil ◽  
Fatty Acid Methyl Esters ◽  
Methyl Esters ◽  
Epoxy Fatty Acid ◽  
Acid Methyl ◽  
System P ◽  
Oil Derivatives

A green synthesis of bio-aldehydes from vegetable oil derivatives is provided by a WO3/H2O2-based “release and capture” catalytic system.

Direct C(sp3)–H Activation of Carboxylic Acids

Synthesis ◽  
2019 ◽  
Vol 52 (04) ◽  
pp. 479-488 ◽  
Author(s):  
Alexander Uttry ◽  
Manuel van Gemmeren
Keyword(s):  
Carboxylic Acid ◽  
General Solution ◽  
Carboxylic Acids ◽  
Bond Activation ◽  
Acid Moiety ◽  
Group Approach ◽  
Research Fields ◽  
Directing Group ◽  
Aliphatic Carboxylic Acids

Carboxylic acids are important in a variety of research fields and applications. As a result, substantial efforts have been directed towards the C–H functionalization of such compounds. While the use of the carboxylic acid moiety as a native directing group for C(sp2)–H functionalization reactions is well established, as yet there is no general solution for the C(sp3)–H activation of aliphatic carboxylic acids and most endeavors have instead relied on the introduction of stronger directing groups. Recently however, novel ligands, tools, and strategies have emerged, which enable the use of free aliphatic carboxylic acids in C–H-activation-based transformations.1 Introduction2 Challenges in the C(sp3)–H Bond Activation of Carboxylic Acids3 The Lactonization of Aliphatic Carboxylic Acids4 The Directing Group Approach5 The Direct C–H Arylation of Aliphatic Carboxylic Acids6 The Direct C–H Olefination of Aliphatic Carboxylic Acids7 The Direct C–H Acetoxylation of Aliphatic Carboxylic Acids8 Summary

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