Ruthenium-Catalyzed Annulation of N-Cbz Hydrazones via C–H/N–N Bond Activation for the Rapid Synthesis of Isoquinolines

Synthesis ◽  
2019 ◽  
Vol 51 (12) ◽  
pp. 2506-2514 ◽  
Author(s):  
Dewal S. Deshmukh ◽  
Bhalchandra M. Bhanage
Keyword(s):  
Functional Group ◽  
Bond Activation ◽  
Strategy Use ◽  
Environmentally Benign ◽  
Catalyst Loading ◽  
Green Solvent ◽  
Rapid Synthesis ◽  
Ru Catalyst ◽  
Internal Alkynes ◽  
Directing Group

In this work, N-Cbz hydrazone has been employed as a rarely explored directing group for the synthesis of isoquinolines by annulation with internal alkynes via C–H/N–N activation using Ru catalyst. Additive as well as external oxidant-free rapid protocol has been established for the synthesis of isoquinolines using microwave strategy. Use of non-volatile and biodegradable PEG as a green solvent with lower catalyst loading makes the proposed protocol environmentally benign. Further, higher functional group tolerance and wide substrate scope has been observed under the stated methodology with higher yields.

scholarly journals C–H and N–H Bond Annulation of Benzamides with Isonitriles Catalyzed by Cobalt(III)

Synthesis ◽  
2017 ◽  
Vol 49 (17) ◽  
pp. 3937-3944 ◽  
Author(s):  
Deepti Kalsi ◽  
Nagaraju Barsu ◽  
Pardeep Dahiya ◽  
Basker Sundararaju
Keyword(s):  
Functional Group ◽  
Bond Activation ◽  
Green Solvent ◽  
Tert Butyl ◽  
Mild Conditions

A simple efficient, atom-economical procedure was developed for the cobalt-catalyzed C–H bond annulation of benzamides with isonitriles under mild conditions. The reaction tolerates a variety of functional group including heterocycles. Diverse 3-(alkylimino)-2-quinolin-8-yl-2,3-dihydro-1H-isoindol-1-ones were synthesized using isonitriles as the C1 source through C–H and N–H bond annulation via C–H bond activation in a ‘green’ solvent. Vinylamides were also used similarly with tert-butyl isonitrile to give 3-(tert-butylimino)-1-quinolin-8-yl-1H-pyrrol-2(5H)-ones.

A removable directing group-assisted Rh(iii)-catalyzed direct C–H bond activation/annulation cascade to synthesize highly fused isoquinolines

2020 ◽  
Vol 7 (20) ◽  
pp. 3186-3192
Author(s):  
Yilang Cheng ◽  
Xu Han ◽  
Junyou Li ◽  
Yu Zhou ◽  
Hong Liu
Keyword(s):  
Functional Group ◽  
Bond Activation ◽  
Directing Group

A removable directing group-assisted Rh(iii)-catalyzed direct C–H bond activation/annulation cascade was developed to synthesize highly fused isoquinolines with good to excellent yields and a good functional group tolerance.

Palladium-Catalyzed ortho-Monoacylation of Arenes with Aldehydes­ via 1,2,4-Benzotriazine-Directed C–H Bond Activation

Synthesis ◽  
2020 ◽  
Vol 52 (09) ◽  
pp. 1407-1416
Author(s):  
Bingcun Cui ◽  
Guosheng Huang ◽  
Jin Liu ◽  
Shaofen Jin ◽  
Yingxing Zhou ◽  
...  
Keyword(s):  
Functional Group ◽  
Bond Activation ◽  
Alternative Strategy ◽  
Bond Functionalization ◽  
Direct Modification ◽  
Palladium Catalyzed ◽  
Directing Group

An efficient palladium-catalyzed C–H bond functionalization/ortho-monoacylation reaction of 3-aryl-1,2,4-benzotriazines with (hetero)aryl or alkyl aldehydes has been developed, which offers a facile and alternative strategy for direct modification and further diversification of 3-aryl-1,2,4-benzotriazines. Bioactive 1,2,4-benzotriazine has been employed as a novel directing group for the palladium-catalyzed regioselective monoacylation of sp2 C–H bond protocol with broad substrate scope and good functional group tolerance.

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>

Exogenous Directing Group Free, Ligand-Enabled gamma-C(sp3)–H Arylation of Free Primary Aliphatic Amines and α-Amino Esters

2019 ◽  
Author(s):  
Yongzheng Ding ◽  
Shuai Fan ◽  
Xiaoxi Chen ◽  
yuzhen gao ◽  
Gang Li
Keyword(s):  
Amino Acids ◽  
Large Scale ◽  
Free Ligand ◽  
Aliphatic Amines ◽  
Rapid Synthesis ◽  
Amino Esters ◽  
Directing Group ◽  
Large Scale Synthesis ◽  
Primary Aliphatic Amines

A Pdᴵᴵ-catalyzed, ligand-enabled gamma-C(sp3)–H arylation of free primary aliphatic amines and amino esters without using an exogenous directing group is reported. This reaction is compatible with unhindered free aliphatic amines, and it is also be applicable to the rapid synthesis of biologically and synthetically valuable unnatural α-amino acids. Large scale synthesis is also feasible using this method.<br>

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.

Palladium-catalyzed Sonogashira coupling of amides: access to ynones via C–N bond cleavage

2016 ◽  
Vol 52 (81) ◽  
pp. 12076-12079 ◽  
Author(s):  
Ming Cui ◽  
Hongxiang Wu ◽  
Junsheng Jian ◽  
Hui Wang ◽  
Chao Liu ◽  
...  
Keyword(s):  
Functional Group ◽  
Bond Cleavage ◽  
Catalyst Loading ◽  
Sonogashira Coupling ◽  
Broad Array ◽  
Palladium Catalyzed ◽  
Low Catalyst Loading

The first palladium-catalyzed Sonogashira coupling of amides has been developed, which proceeds via a selective cleavage of the N-acylsaccharin C–N bond. The protocol is mild, highly functional group tolerant and can be efficiently employed in the synthesis of a broad array of ynones in 48–98% yields under low catalyst loading and Cu-free conditions.

scholarly journals Iron-Catalyzed C(sp2)–C(sp3) Cross-Coupling of Aryl Chlorobenzoates with Alkyl Grignard Reagents

Molecules ◽  
2020 ◽  
Vol 25 (1) ◽  
pp. 230 ◽  
Author(s):  
Elwira Bisz ◽  
Michal Szostak
Keyword(s):  
Organic Synthesis ◽  
Nucleophilic Addition ◽  
Functional Group ◽  
High Selectivity ◽  
Cross Coupling ◽  
Environmentally Benign ◽  
Grignard Reagents ◽  
High Importance ◽  
Iron Salts ◽  
The Cross

Aryl benzoates are compounds of high importance in organic synthesis. Herein, we report the iron-catalyzed C(sp2)–C(sp3) Kumada cross-coupling of aryl chlorobenzoates with alkyl Grignard reagents. The method is characterized by the use of environmentally benign and sustainable iron salts for cross-coupling in the catalytic system, employing benign urea ligands in the place of reprotoxic NMP (NMP = N-methyl-2-pyrrolidone). It is notable that high selectivity for the cross-coupling is achieved in the presence of hydrolytically-labile and prone to nucleophilic addition phenolic ester C(acyl)–O bonds. The reaction provides access to alkyl-functionalized aryl benzoates. The examination of various O-coordinating ligands demonstrates the high activity of urea ligands in promoting the cross-coupling versus nucleophilic addition to the ester C(acyl)–O bond. The method showcases the functional group tolerance of iron-catalyzed Kumada cross-couplings.

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