N-arylation Of Amines Research Articles

An eco-friendly convenient approach for the synthesis of guar gum integrated copper nanoparticles: Investigation of its catalytic activity in the C[sbnd]N Ullmann coupling reactions and study of its anti-human kidney cancer effects

We carried out this research was in order to evaluate the potency of guar gum (GG) hydrogel to conduct CuO NPs synthesis by adopting an eco-friendly approach as well as to study its role as catalyst and in relieving cancerous cell lines. In this context, we accomplished the CuO NPs/GG synthesis by employing a simple one-step approach and identified its characters through UV–Visible (UV–Vis) spectroscopy, X-ray diffraction (XRD), transmission electronic microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-rays spectroscopy (EDS), elemental mapping and ICP-OES analysis. XRD and TEM results of CuO NPs/GG showed the face centered cubic (fcc) structures and predominantly spherical shaped with a size of 20–30 nm. After the characterization, the prepared CuO NPs/GG nanocatalyst was used as catalyst in the N-arylation of amines (indole and imidazoles) through C(aryl)-N chemical bond arrangement from the related aryl halides (I, Br, Cl) by Ullmann-type coupling reactions. It is worth mentioning that the novel catalyst has the potential of being recycled seven times without much change in activity. Furthermore, the anti-kidney cancer properties of CuO NPs/GG nanocomposite were assessed by MTT assay about the cytotoxicity and anti-human on normal (HUVEC) and human kidney cell lines i.e. ACHN, CaKi-2 and HEC293. The corresponding IC50 values were 18.5, 17.2, and 15.6 µg/mL, respectively. The viability of malignant human kidney cell line reduced dose-dependently in the presence of the nano bio-composite. After clinical study, CuO NPs/GG nano bio-composite can be utilized as an efficient drug in the treatment of human kidney cancer in human.

On the Current Status of Ullmann-Type N-Arylation Reactions Promoted by Heterogeneous Catalysts

Ullmann-type C–N heterocoupling reactions have been applied for the syntheses of N-arylated amines. In the past decade, transition metal-catalyzed N-arylations have been recognized as particularly efficient procedures for the preparation of nitrogen-containing aromatic systems. These reactions typically carried out under optimized conditions, have also been found to be suitable for the synthesis of complex molecules with other functional groups, including natural products, drugs, or pharmaceuticals. Most importantly, copper-catalyzed N-arylations have been studied and employed in the total synthesis of biologically active compounds. The construction of fused N-heterocyclic compounds also remained the subject of extensive research because of their potential applications in drug discovery and the development of functional materials. The aim of this review is to summarize the recent progress in the synthetic applications of Ullmann-type N-arylation reactions performed in heterogeneous systems. In particular, the utilization of copper and palladium species immobilized on various support materials, modified by surface functionalization, has been discussed and evaluated.

Sulfate radical anion-induced benzylic oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines.

A mild, operationally convenient, and practical method for the synthesis of synthetically useful N-arylsulfonylimines from N-(arylsulfonyl)benzylamines using K2S2O8 in the presence of pyridine as a base is reported herein. In addition, a "one-pot" tandem synthesis of pharmaceutically relevant N-heterocycles by the reaction of N-arylsulfonylimines, generated in situ with ortho-substituted anilines is also reported. The key features of the protocol include the use of a green oxidant, a short reaction time (30 min), chromatography-free isolation, scalability, and economical, delivering N-arylsulfonylimines in excellent yields of up to 96%. While the oxidation of N-aryl(benzyl)amines to N-arylimines using K2S2O8 is reported to be problematic, the oxidation of N-(arylsulfonyl)benzylamines to N-arylsulfonylimines using K2S2O8 has been achieved for the first time. The dual role of the sulfate radical anion (SO4·-), including hydrogen atom abstraction (HAT) and single electron transfer (SET), is proposed to be involved in the plausible reaction mechanism.

Fine Tuning of Quantum Dots Photocatalysts for the Synthesis of Tropane Alkaloid Skeletons.

Several types of Quantum Dots (QDs) (CdS, CdSe and InP, as well as core-shell QDs such as type I InP-ZnS, quasi type-II CdSe-CdS and inverted type-I CdS-CdSe) were considered for generating α-aminoalkyl free radicals. The feasibility of the oxidation of the N-aryl amines and the generation of the desired radical was evidenced experimentally by quenching of the photoluminescence of the QDs and by testing a vinylation reaction using an alkenylsulfone radical trap. The QDs were tested in a radical [3+3]-annulation reaction giving access to tropane skeletons and that requires the completion of two consecutive catalytic cycles. Several QDs such as CdS core, CdSe core and inverted type I CdS-CdSe core-shell proved to be efficient photocatalysts for this reaction. Interestingly, the addition of a second shorter chain ligand to the QDs appeared to be essential to complete the second catalytic cycle and to obtain the desired bicyclic tropane derivatives. Finally, the scope of the [3+3]-annulation reaction was explored for the best performing QDs and isolated yields that compare well with classical iridium photocatalysis were obtained.

Electrochemical dual α,β-C(sp3)–H functionalization of cyclic N-aryl amines

Herein, a straightforward route for dual α,β-C(sp3)–H functionalized cyclic N-aryl amines using a combination of electrocatalysis and iron catalysis is disclosed, setting the stage for the challenging multiple site selective C–H functionalization.

Hydride-Abstraction-Initiated Catalytic Stereoselective Intermolecular Bond-Forming Processes.

The stereoselective intermolecular bond-forming reactions through the direct manipulation of ubiquitous yet inert C(sp3)-H bonds represent an important and long-standing goal in chemistry. In particular, developing such a stereoselective bimolecular transformation involving carbocation intermediates generated via site-selective hydride abstraction or formal hydride abstraction by organic oxidants would avoid the preinstallation of directing groups and is therefore attractive. Hydride-abstraction-initiated bimolecular transformations have received considerable attention, but existing examples lack stereoselective studies. Prevalent stereoselective studies typically suffer from the narrow substrate scope of specific and highly reactive N-aryl amines and diarylmethanes together with limited synthetic utility. This Account describes our recent advances in the development and synthetic application of hydride-abstraction-initiated stereoselective intermolecular C-C and C-H bond-forming processes with significantly expanded scopes involving structurally diverse N-acyl amines and ethers together with nitriles, esters, and perfluoroalkyl moieties.We first explored hydride-abstraction-initiated stereoselective intermolecular C-C bond-forming processes. Utilizing triarylmethyl cations or oxoammonium ions as hydride abstractors, we accomplished the diastereoselective oxidative C-H functionalization of structurally diverse N-acyl amines and ethers with a range of organoboranes and C-H components, efficiently installing a series of alkyl, alkenyl, aryl, and alkynyl species into the α-position of heteroatoms with good levels of diastereocontrol. Subsequently, we developed an "acetal pool" strategy as the toolbox to regulate the stability of cationic intermediates and the compatibility of organic oxidants with a delicate asymmetric catalysis system. Utilizing this strategy, we achieved the catalytic enantioselective oxidative C-H alkenylation, arylation, alkynylation, and alkylation of diverse N-acyl heterocycles with a range of boronates and C-H components. Simultaneously, we extended this strategy to the asymmetric oxidative C-H alkylation of ethers. Notably, the method allows solvents that are used daily, such as tetrahydrofuran, tetrahydropyran, and diethyl ether, to be facilely transformed to high-value-added optically pure bioactive molecules. We further expanded the scope of this challenging area from the C(sp3)-H bond adjacent to electron-donating heteroatoms to valuable electron-withdrawing functional groups including nitriles, esters, and perfluoroalkyl moieties for the stereoselective construction of single and vicinal quaternary carbon stereocenters, respectively.We studied hydride-abstraction-initiated catalytic asymmetric intermolecular C-H bond-forming processes, known as redox deracemization. Utilizing the acetal pool strategy, we reported the first redox deracemization of cyclic benzylic ethers. Later, we disclosed an aerobic one-pot deracemization of diverse α-amino acid derivatives with excellent functional group compatibility. We further achieved the deracemization of the tertiary stereogenic center adjacent to electron-withdrawing groups including perfluoroalkyl, cyano, and ester moieties, which are otherwise difficult to construct.

Magnetic MCR-Functionalized Graphene Oxide Complexed with Copper Nano-Particles: An Efficient and Recyclable Nanocatalyst for Ullmann C–N Coupling Reaction

In this study, we report the synthesis of Cu nanoparticle modified dithiocarbamate (DTC)-functionalized magnetic graphene oxide (GO) nanocatalyst through a one-pot three component reaction. It has an excellent affinity for copper nanoparticles due to its DTC ligand amide motif. The structure of the synthesized catalysts was confirmed by using FT-IR, TGA, CHNS, SEM, XRD, EDS mapping, and ICP. The catalytic activity of the synthesized nanocatalyst was investigated in Ullmann cross-coupling reaction for the synthesis of N-aryl amines, which resulted in high reaction yields, easy workup, and short reaction times. The catalyst is separated easily by a magnetic field and can be reused for at least five successive runs without significant loss of catalytic activity. The nature of the supported DTC on the GO’s surface improved the catalytic activity of the graphene, provided homogeneity to the catalyst, and enhanced the capability of coordination with copper ions. Facile catalyst recovery and reusability, simple setup procedure, generality of the method and high turnover number (TON) make this procedure an environmentally benign approach for preparing the titled compounds. Based on the findings of this study, it appears that the catalytic system introduced can be used to prepare other beneficial heterocyclic compounds.

Frontispiece: Electrochemical Desaturative β‐Acylation of Cyclic N‐Aryl Amines

Electrochemistry. An electrochemical desaturative α-acylation of cyclic N-aryl amines to access α-substituted enamines is reported in the Communication by Youai Qiu et al. (e202115178).

Synthesis of N-aryl amines enabled by photocatalytic dehydrogenation.

Catalytic dehydrogenation (CD) via visible-light photoredox catalysis provides an efficient route for the synthesis of aromatic compounds. However, access to N-aryl amines, which are widely utilized synthetic moieties, via visible-light-induced CD remains a significant challenge, because of the difficulty in controlling the reactivity of amines under photocatalytic conditions. Here, the visible-light-induced photocatalytic synthesis of N-aryl amines was achieved by the CD of allylic amines. The unusual strategy using C6F5I as an hydrogen-atom acceptor enables the mild and controlled CD of amines bearing various functional groups and activated C–H bonds, suppressing side-reaction of the reactive N-aryl amine products. Thorough mechanistic studies suggest the involvement of single-electron and hydrogen-atom transfers in a well-defined order to provide a synergistic effect in the control of the reactivity. Notably, the back-electron transfer process prevents the desired product from further reacting under oxidative conditions.

A Mechanistic Analysis of the Palladium-Catalyzed Formation of Branched Allylic Amines Reveals the Origin of the Regio- and Enantioselectivity through a Unique Inner-Sphere Pathway.

A recently reported palladium-catalyzed allylic substitution of vinyl-substituted cyclic carbonates (VCCs) with aryl amines represents a rare example of a regio- and enantioselective synthesis of α,α-disubstituted allylic N-aryl amines. However, the underlying reasons for this unusual selectivity profile remain elusive. In the present work, density functional theory (DFT) calculations in combination with mechanistic control experiments were performed to elucidate in detail this allylic amination manifold and the origin of the regio- and enantioselectivity. The combined data show that after oxidative addition of the VCC to Pd0 , the nucleophilic attack via an originally proposed outer-sphere pathway gives, however, the opposite regioisomer compared to the experimental results. Instead, nucleophilic attack of the amine reagent via a unique type of chelation-assisted, inner-sphere pathway accounts for the experimentally observed "branched" regioselectivity and high enantio-control.

One-Pot Synthesis of N-Arylated Amines by Hydroaminomethyl­ation of 2,5-Dihydrofuran with Aromatic Amines

A new efficient catalytic system for one-step synthesis of N-arylated amines, for example, an important intermediate, 4-ethyl-N-[(tetrahydrofuran-3-yl)methyl]aniline, is achieved by using different rhodium precursor and phosphorus ligands catalyzed hydroaminomethylation of aniline and its derivatives with heterocyclic and/or cyclic olefins. By screening the reaction parameters, the optimal reaction conditions are found as follows: methanol as a solvent, PPh3 as a ligand, [Rh(cod)2]BF4 as a catalyst precursor, a P/Rh ratio of 5:1, syngas pressure 4 MPa (H2/CO = 3:1), 100 °C, 20 hours, and no additives. The conversion of aniline reaches >99% and the yield of N-[(tetrahydrofuran-3-yl)methyl]aniline is up to 99% using this catalytic system. Moreover, the reaction of aniline and various cyclic olefins is investigated under the optimal conditions, and excellent conversion and good yields are obtained.

Design of BNPs-TAPC Palladium Complex as a Reusable Heterogeneous Nanocatalyst for the O-Arylation of Phenols and N-Arylation of Amines

The thermally stable new heterogenous nanocatalyst BNPs@SiO2(CH2)3-TAPC-O-CH2CH2NH2-Pd(0) was synthesized, characterized and successfully applied in carbon-heteroatom (C–O and C–N) coupling reactions of aryl halides with phenols and amines. The formation of resultant nanocatalyst was approved by FT-IR, XRD, TGA, XPS and EDX techniques. The morphology of BNPs@SiO2(CH2)3-TAPC-O-CH2CH2NH2-Pd(0) was characterized using scanning and transmission electron microscopes. The leaching of palladium from the surface of the catalyst was studid by ICP-OES technique. Noteworthy, the highly active BNPs@SiO2(CH2)3-TAPC-O-CH2CH2NH2-Pd(0) can be easily recycled and reused for six times with negligible loss in its activity. Some remarkable advantages of this method are the shorter reaction times, milder conditions, no needs for an inert atmosphere, high yields and easy separation.

Tetrabutylammonium Bromide-Promoted Metal-Free, Efficient, Rapid, and Scalable Synthesis of N-Aryl Amines.

A rapid, transition metal-free, high-yielding, tetrabutylammonium bromide-promoted method of N-arylation is reported within. The optimized conditions tolerated a wide range of secondary amines and was equally effective with bromo- and chlorobenzene-including substituted aryl halides. The developed method is found to be effective for N-arylation when compared to earlier methods which involve harsh conditions, transition metals, lack of scalability, and long reaction times. Our method utilizes conventional heating only; it is readily scalable; and the products are facile to purify.

Magnetic Ugi-functionalized graphene oxide complexed with copper nanoparticles: Efficient catalyst toward Ullman coupling reaction in deep eutectic solvents

Herein, we report the direct synthesis of carboxamide-functionalized graphene oxide (carboxamide-f-GO) for the development of new nanocatalysts, with highly dispersed particles, through covalent functionalization with a facile and direct strategy. This surface functionalization was carried out through a one-pot sequential four-component Ugi reaction. Subsequently, the Ugi-ligand decorated on the surface of the graphene oxide sheets coordinated with copper nanoparticles (Cu NPs) and finally covered with magnetic nanoparticles. The synthesized nanocatalyst was characterized by Fourier transform infrared (FT-IR), proton nuclear magnetic resonance spectroscopy (1H NMR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), dynamic light scattering (DLS), thermogravimetric analysis (TGA) and atomic force microscopy (AFM). The carboxamido nitrogen in Ugi-ligand showed high affinity toward complexation with Cu NPs and has a profound effect on the reactivity of the copper center in this nanocatalyst. The catalytic activity of nanocatalyst was investigated in Ullmann cross-coupling reaction for practical and direct access to corresponding N-aryl amines in a deep eutectic solvent as a green and recyclable media. The results showed the capability of this designed catalytic system through N-arylation of N-heterocycles and aniline derivatives with high yields in short reaction times. In addition, both of the nanocatalyst and deep eutectic solvent were easily recovered and reused for five consecutive runs.

Photoredox-Controlled Mono- and Di-Multifluoroarylation of C(sp3 )-H Bonds with Aryl Fluorides.

A controllable mono- and di-multifluoroarylation of acyclic and cyclic N-aryl amines with aryl fluorides by photocatalyzed dual C(sp3 )-H/C(sp2 )-F functionalization has been developed, providing new access to a wide array of valuable α-fluoroarylated amines. In addition, the one-pot consecutive hetero-di-multifluoroarylation of N-aryl pyrrolidines and N,N-dimethylanilines was achieved with high to excellent diastereoselectivity. This new defluorinative C(sp3 )-C(sp2 ) coupling is distinguished by a broad scope, good regioselectivity, and mild conditions as well as gram-scale and late-stage applicability, and thus constitutes a significant advance in the arylation of unactivated C(sp3 )-H bonds with aryl fluorides.

WITHDRAWN: SiO2 functionalized melamine-pyridine groups-supported Cu(OAc)2 as an efficient heterogeneous and recyclable nanocatalyst for N-arylation of amines through Ullmann coupling reactions

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Deep Eutectic Solvent/Lipase: Two Environmentally Benign and Recyclable Media for Efficient Synthesis of N-Aryl Amines

Deep eutectic solvent (DES)/lipase catalyzed efficient synthesis of N-aryl amines from electron deficient aryl chlorides and amines at ambient temperature is reported. Its significant features include excellent yields of products, use of biodegradable, non-toxic and recyclable catalysts, thereby avoiding toxic metal catalyst/solvents making these protocols environmentally benign.

High Catalytic Activity of Peptide Nanofibres Decorated with Ni and Cu Nanoparticles for the Synthesis of 5-Substituted 1H-Tetrazoles and N-Arylation of Amines

A rapid development of a new methodology for decarboxylative N-arylation of carboxylic acids and the preparation of 5-substituted 1H-tetrazoles catalysed by peptide nanofibres decorated with Cu and Ni nanoparticles is presented. Compared with conventional aryl halides, benzoic acids are extremely interesting and environmentally friendly options for the synthesis of secondary aryl amines.

CoPc/Cu(OAc)2-catalyzed N-arylation of amines with arylhydrazines leading to N-aryl amines

The N-arylation of amines with arylhydrazines has been developed, achieving the selective cross-coupling of aryl radicals with amines to form N-aryl amines. The reaction uses air as an oxidant, CoPc and Cu(OAc)2 as catalysts. The reaction proceeds under mild conditions in air through a relay process, arylhydrazines are oxidized to aryldiazenes by CoPc, further oxidized to aryl radicals by air (O2), which are trapped by Cu(OAc)2–amine complex, followed by reduction–elimination reaction to form N-aryl amines. Arylamines and arylhydrazines give the highest yields, but N-aryl-N-alkylamines and N-alkylamines can be used as well.

Direct Acylation of C(sp(3))-H Bonds Enabled by Nickel and Photoredox Catalysis.

Using nickel and photoredox catalysis, the direct functionalization of C(sp(3))-H bonds of N-aryl amines by acyl electrophiles is described. The method affords a diverse range of α-amino ketones at room temperature and is amenable to late-stage coupling of complex and biologically relevant groups. C(sp(3))-H activation occurs by photoredox-mediated oxidation to generate α-amino radicals which are intercepted by nickel in catalytic C(sp(3))-C coupling. The merger of these two modes of catalysis leverages nickel's unique properties in alkyl cross-coupling while avoiding limitations commonly associated with transition-metal-mediated C(sp(3))-H activation, including requirements for chelating directing groups and high reaction temperatures.