Copper-in-Charcoal (Cu/C) Promoted Diaryl Ether Formation

Microwave-Assisted Cu-Catalyzed Diaryletherification for Facile Synthesis of Bioactive Prenylated Diresorcinols

Prenylated diresorcinols exhibit various bioactivities, including cytotoxic, antibacterial, and antifungal activities. Therefore, establishing facile and efficient synthetic routes for prenylated diresorcinols facilitates their development as chemical probes or drugs with a novel mode of action. In this study, microwave-assisted copper catalysis was explored as a cost-effective and environmentally friendly method for the cross-coupling of sterically hindered ortho-prenylated phenols and aryl halides to produce bioactive prenylated diresorcinols, diorcinol I and leotiomycene B. Notable advantages of microwave-assisted catalysis include not only operational simplicity and rapid heating but also shorter reaction times and higher chemical yields. In addition, highly regioselective prenylation of phenol was achieved for the preparation of ortho-prenyl phenol via directed lithiation and subsequent alkylation. This study provides valuable insights for the preparation of other bioactive prenylated diresorcinols. Furthermore, considering that prenylated benzenoids are biosynthetic precursors of various polycyclic natural products, this synthetic route could be expanded to more complex bioactive compounds possessing diaryl ethers.

Copper-catalyzed N-arylation of indoles

Abstract:

Over the past decades, the N-arylation of indoles has gained an inevitable role in the fields of material science, pharmaceuticals, and agrochemical industries. They are the basic core skeleton of many natural products. Their synthesis by Ullmann-type C–N coupling reaction of indole derivatives with aryl halides through various catalytic protocols is well explored. Transition metal catalysis was the best method for synthesizing 1-aryl indoles, and copper catalysis is the leading among them. This review comprehends the recent developments in the copper-catalyzed C–N cross-coupling of indoles with aryl halides from 2010 to 2022.

Copper on charcoal: Cu0 nanoparticle catalysed aerobic oxidation of α-diazo esters

By using a charcoal supported nano Cu⁰ catalyst (Cu/C), a highly efficient oxidation of α-diazo esters to α-ketoesters with molecular oxygen as the sole oxidant has been developed. In the presence of the Cu/C catalyst, 2-aryl-α-diazo esters with both electron-donating and electron-withdrawing groups can be oxidized to the corresponding α-ketoesters efficiently. Furthermore, this Cu/C catalyst can catalyse the reaction of aryl α-diazo ester with water to form aryl ketoester, 2-aryl-2-hydroxyl acetate ester and 2-aryl acetate ester. In this case, water is split by α-diazo ester, and the diazo group is displaced by the oxygen or hydrogen atom in water. Mechanistic investigation showed that the reaction of α-diazo ester with oxygen proceeds through a radical pathway. In the presence of 2,2,6,6-tetramethyl piperidine nitrogen oxide, the reaction of α-diazo ester with oxygen is dramatically inhibited. Furthermore, the reaction of α-diazo ester with water is investigated by an isotopic tracer method, and GCMS detection showed that a disproportionation reaction occurred between α-diazo ester and water.

The Influence of Copper on Halogenation/Dehalogenation Reactions of Aromatic Compounds and Its Role in the Destruction of Polyhalogenated Aromatic Contaminants

The effect of copper and its compounds on halogenation and dehalogenation of aromatic compounds will be discussed in the proposed article. Cu oxidized to appropriate halides is an effective halogenation catalyst not only for the synthesis of halogenated benzenes or their derivatives as desired organic fine chemicals, but is also an effective catalyst for the undesirable formation of thermodynamically stable and very toxic polychlorinated and polybrominated aromatic compounds such as polychlorinated biphenyls, dibenzo-p-dioxins and dibenzofurans accompanied incineration of waste contaminated with halogenated compounds or even inorganic halides. With appropriate change in reaction conditions, copper and its alloys or oxides are also able to effectively catalyze dehalogenation reactions, as will be presented in this review.

Cyanide Ion-Promoted Nucleophilic Displacement of Aromatic Nitro Groups: A Mild, One-Pot, Transition Metal-Free Synthesis of Nitrile-Containing Naphthalimide Aryl Ether Derivatives

Herein we report the novel synthesis of nitrile-containing naphthalimide aryl ether derivatives via transition metal-free cyanide ion-promoted nucleophilic displacement of nitronaphthalimide with alcohols or phenols. The transformation involves a one-pot reaction, which is operationally simple and mild and bereft of transition metal catalysts. This work provides a novel route for the preparation of diaryl ether derivatives.

A post-synthetically modified metal–organic framework for copper catalyzed denitrative C–N coupling of nitroarenes under heterogeneous conditions

Post-synthesis modification of DMOF, afforded a desired material for strategic infusion of catalytically active centers in a porous matrix. The catalyst is capable for denitrative C–N coupling reactions of nitroarenes under heterogeneous conditions.

Bio-based Catalysts from Biomass Issued after Decontamination of Effluents Rich in Copper—an Innovative Approach towards Greener Copper-based Catalysis

The abundance of Cu-contaminated effluents and the serious risk of contamination of the aquatic systems combine to provide strong motivating factors to tackle this environmental problem. The treatment of polluted effluents by rhizofiltration and biosorption is an interesting ecological alternative. Taking advantage of the remarkable ability of the selected plants to bioconcentrate copper into roots, these methods have been exploited for the decontamination of copperrich effluents. Herein, we present an overview on the utility of the resulted copper-rich biomass for the preparation of novel bio-sourced copper-based catalysts for copper-mediated reactions: from the bioaccumulation of copper in plant, to the preparation and full analysis of the new Eco-Cu catalysts, and their application in selected key reactions. The hydrolysis of a thiophosphate, an Ullmanntype coupling leading to N- and O-arylated compounds, and a CuAAC “click” reaction, all performed under green and environmentally friendly conditions, will be described.

Practical Synthesis of Chromeno[2,3-b]indole Skeleton via an Aldehyde Group Insertion/Aromatization Strategy

The synthesis of chromeno[2,3-b]indole from simple starting materials remains a demanding process. Herein, 2-bromoindole undergoes nucleophilic attack from salicylaldehyde, followed by intramolecular insertion of an aldehyde group and aromatization to generate the desired chromeno[2,3-b]indoles. Moreover, various functional groups were tolerated and a gram-scale synthesis of the product could be achieved under the optimized condition.

An operational transformation of 3-carboxy-4-quinolones into 3-nitro-4-quinolones via ipso-nitration using polysaccharide supported copper nanoparticles: synthesis of 3-tetrazolyl bioisosteres of 3-carboxy-4-quinolones as antibacterial agents

The 3-nitro-4-quinolones have been synthesized via ipso nitration of 3-carboxy-4-quinolones by chitosan supported Cu nano-particles. The 3-nitro derivatives were converted into their 3-tetrazolyl bioisosteres which showed increased antibacterial activity.

Ullmann reaction through ecocatalysis: insights from bioresource and synthetic potential

We report the elaboration of novel bio-sourced ecocatalysts for the Ullmann coupling reaction.

Microwave-assisted synthesis of macrocycles via intramolecular and/or bimolecular Ullmann coupling

Microwave-assisted synthesis of macrocyclic diaryl ethers via intramolecular and/or bimolecular Ullmann coupling is described. Using the optimized conditions, a panel of macrocycles, with different substitution patterns, ring sizes, and linkers, has been successfully synthesized using microwave irradiation. To the best of our knowledge, this work represents the first examples of the microwave-assisted synthesis of macrocyclic diaryl ethers via intramolecular and/or bimolecular Ullmann coupling.

Cu-catalyzed arylation of phenols: synthesis of sterically hindered and heteroaryl diaryl ethers

Cu-catalyzed O-arylation of phenols with aryl iodides and bromides can be performed under mild condition in DMSO/K(3)PO(4) with use of picolinic acid as the ligand for copper. This method tolerates a variety of functional groups and is effective in the synthesis of hindered diaryl ethers and heteroaryl ethers.