Coupling Reaction Of Amines Research Articles

Metal free biomimetic deaminative direct C-C coupling of unprotected primary amines with active methylene compounds.

An unprecedented direct C-C coupling reaction of unprotected primary amines with active methylene compounds is reported. The reaction involves a biomimetic deamination of amines which was achieved under conditions free of metallic reagents and strong oxidizing agents. A wide range of primary amines was reacted with different active methylene compounds to provide structurally diverse trisubstituted alkenes and dihydropyridines. A kinetic study revealed an activation barrier of 10.1 kcal mol-1 for the conversion of a key intermediate of the reaction.

Iodine-mediated oxidative N-N coupling of secondary amines to hydrazines.

An I2-mediated N-N coupling reaction has been established for oxidative dimerization of N-aryl aminopyridines to a variety of novel hydrazine derivatives under mild conditions. This synthetic method does not require use of transition metals and can be conveniently carried out on a gram scale. It is also applicable to diphenylamine and N-alkyl aniline substrates.

A comparative study on atomically precise Au nanoclusters as catalysts for the aldehyde-alkyne-amine (A3) coupling reaction: ligand effects on the nature of the catalysis and efficiency.

Atomically precise Au13 nanoclusters stabilized by stibines catalyze the aldehyde–alkyne–amine coupling reaction more efficiently than those stabilized by thiols or phosphines. The nature of the catalytic activity is also different, and may be attributed to the weaker coordinating ability of the stibine ligands.

Synthesis of a magnetic-based yolk-shell nano-reactor: A new class of monofunctional catalyst by Cu0-nanoparticles and its application as a highly effective and green catalyst for A3 coupling reaction

A novel and yolk/shell nanoreactor catalyst (H-Fe3O4@h-Cu0@m-SiO2) was designed and synthesized with a hollow magnetite core encapsulated in a mesoporous silica shell which Cu0-nanoparticles were decorated in the interior cavity shell in order to enhance the catalytic activity. The morphology, structure and physicochemical properties of the yolk/shell nanoreactor were then fully characterized by using high resolution transmission electron microscopy (HRTEM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction patterns (XRD), Fourier transform infrared spectroscopy (FT-IR). The N2 absorption-desorption isotherms indicate a Brunauer–Emmett–Teller (BET) specific surface area of 287.36 m2/g and a pore width of 2–50 nm. Applied as a catalyst for three-component A3 coupling reaction of alkynes, aldehydes and amines under the optimized condition. Interestingly, the characterization results indicate that (H-Fe3O4@h-Cu0@m-SiO2) has great catalytic performance, which could be related to unique hollow morphology with an active core contains Cu0-nanoparticles, protective mesoporous shell and hollow void. This aspect of morphology leads to favoring the transfer of the reactants and products. Reusability up to 10 times without any obvious decline in catalytic activity and short reaction time are other advantageous of this green nano-reactor.

Immobilized Gold Nanoparticles Prepared from Gold(III)-Containing Ionic Liquids on Silica: Application to the Sustainable Synthesis of Propargylamines.

A cycloaurated phosphinothioic amide gold(III) complex was supported on amorphous silica with the aid of an imidazolium ionic liquid (IL) physisorbed in the SiO2 pores (SiO2–IL) and covalently bonded to the SiO2 (SiO2@IL). Gold(0) nanoparticles (AuNPs) were formed in situ and subsequently immobilized on the SiO2–IL/SiO2@IL phase. The resulting catalytic systems Au–SiO2–IL and Au–SiO2@IL promoted the solvent-free A3 coupling reaction of alkynes, aldehydes, and amines in high yields under solvent-free conditions with very low catalyst loading and without the use of additives. The Au–SiO2@IL catalyst showed good recyclability and could be reused at least five times with yields of propargylamines of ≥80%. This synthetic method provides a green and low cost way to effectively prepare propargylamines. Additionally, 31P high resolution magic angle spinning (HRMAS) NMR spectroscopy is introduced as a simple technique to establish the Au loading of the catalyst.

Copper incorporated into 1H-1,2,3-triazole-5-methanol functionalized halloysite nano clay as an efficient and heterogeneous catalyst for promoting green A3 and KA2 coupling reaction: Optimization of reaction variables using response surface methodology

Abstract Design and synthesis of a novel heterogeneous catalyst based on functionalization of halloysite nanoclay with 1H-1,2,3-triazole-5-methanol and subsequent incorporation of copper is disclosed. The obtained catalyst was fully characterized by employing ICP-AES, SEM/EDX, TGA, XRD, BET and FTIR and successfully used for promoting the A3 and KA2 coupling reactions of phenylacetylene, amines and aldehydes or ketone in aqueous media. The reaction variables including reaction temperature and amount of the catalyst were optimized using Response Surface Methodology (RSM). The catalyst exhibited excellent catalytic activity under optimum reaction condition. Notably, the investigation of the reusability of the catalyst confirmed that the catalyst could be recovered and reused up to four reaction runs with only slight loss of the catalytic activity. The hot filtration experiment also demonstrated low leaching of copper species, indicating the heterogeneous nature of the catalysis. Easy work-up procedures, performing the reaction in aqueous media, broad range of substrate scope and low reaction times are other merits of this protocol.

Oxidation or Reduction State of Au Stabilized by an MOF: Active Site Identification for the Three‐Component Coupling Reaction

AbstractAs one of the most efficient catalysts for the three‐component coupling reaction of aldehyde, amine, and alkyne (A3 coupling), Au has attracted extensive attention, but there is a debating issue on whether Auδ+ (δ > 0, representing the oxidation state of Au species) or Au0 is the better active site. According to previous reports, both Auδ+ and Au0 can catalyze the A3 coupling reaction. Therefore, the establishment of a suitable comparison model to identify the better active site is highly desired. In this work, an ideal model to identify the efficient active sites for the A3 coupling reaction based on a metal–organic framework (MOF) platform is rationally fabricated. The Auδ+ in oxidation state can be well bound to the MOF, MIL‐101‐NH2, via postsynthetic modification, and the Au0 catalyst with retained MOF skeleton can be formed via a subsequent one‐step reduction, which provide ideal comparison models with the only difference in the Au oxidation state. Strikingly, the two catalysts exhibit significant activity difference in the A3 coupling reaction. The activity of Auδ+ catalyst is 11‐fold higher than that of Au0, which reveals that Auδ+ serves as a much more effective active site in the A3 coupling reaction.

Difluoroborate-based conjugated organic polymer: a high-performance heterogeneous photocatalyst for oxidative coupling reactions

A photoactive difluoroborate-based conjugated organic polymer (B-COP) with A3B2-type donor–acceptor arrays in the polymer framework was synthesized by direct polycondensation and exhibited amorphous structure, high thermal and photophysical stability. The B-COP was shown to be a highly efficient heterogeneous photocatalyst for a wide range of photocatalytic transformations, including the oxidative coupling of primary amine and cross-dehydrogenative coupling reactions between tetrahydroisoquinolines and nucleophiles such as nitromethane, nitroethane, acetone and phenylethyl ketone.

Synthesis of β-oxopropylcarbamates in a recyclable AgBr/ionic liquid catalytic system: An efficient assembly of CO2 under ambient pressure

Abstract A green and recyclable catalytic system based on AgBr and an ionic liquid (IL) was developed for the three-component coupling reaction of propargylic alcohols, secondary amines and carbon dioxide (CO2). A series of target carbamates, especially those generated from challenging substrates, could be obtained smoothly at atmospheric CO2 pressure in a straightforward one-pot process. Moreover, the catalyst loading reached the lowermost level ever reported. Particularly, this catalytic system exhibited robust constancy and could be reused at least 5 times with retention of high catalytic activity. It is worth noting that this is the first catalytic system which could be recycled successfully for this reaction.

Spinel copper ferrite nanoparticles: Preparation, characterization and catalytic activity

The magnetic CuFe2O4 nanoparticles have been synthesized and characterized by various spectroscopic methods, including X‐ray diffraction (XRD), O K, Cu and Fe K ‐edge X‐ray absorption near edge structure (XANES), energy dispersive X‐ray analysis (EDX), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The azide‐alkyne cycloaddition by the reaction of various phenylacetylenes with a mixture of benzyl halides and NaN3 and also three component (A3) coupling reaction of aldehyde, alkyne and amine catalyzed by CuFe2O4 nanoparticles under aerobic conditions led to the formation of the 1,4‐disubstituted‐1,2,3‐triazoles and propargylamines in excellent yields. The catalyst can be recovered by applying an external magnetic field for the subsequent cycloaddition reactions and reused without any tangible loss in catalytic efficiency.

CuI@Sulfur-functionalized halloysite nanoclay: a novel recyclable catalyst for the ultrasonic-assisted synthesis of propargylamines: a combination of experimental and DFT simulation

A novel heterogeneous catalyst, CuI supported on sulfur functionalized halloysite (CuI@HNTs-S), was designed and synthesized through functionalization of the halloysite nanoclay surface with 3-mercaptopropyl trimethoxysilane and subsequent immobilization of CuI. The catalyst was characterized by using various characterization techniques such as FTIR, SEM/EDS, XRD, ICP and TGA. The catalytic activity of CuI@HNTs-S for the synthesis of propargylamines through ultrasonic-assisted multi-component A3 coupling reaction of aldehydes, phenyl acetylene and amines was also studied. The results established that CuI@HNTs-S could efficiently catalyze the reaction to furnish the desired products in excellent yield and in short reaction time. Notably the catalyst was recyclable and could be recycled with slight loss of the catalytic activity for five reaction runs. Then, the ability of pristine HNTs and sulfur functionalized HNTs toward CuI grabbing was compared quantitatively using molecular simulation. Calculated energies confirmed better performance of HNTs-S toward CuI physisorption, which decreases its leaching during catalytic reaction. This result was experimentally confirmed by observing the superior recyclability and low copper leaching of CuI@HNTs-S compared to CuI@HNTs.

Total synthesis of Carpatamides A–D

A synthetic strategy was developed for the synthesis of the common core structure of Carpatamides A–D. The total synthesis of Carpatamides A and C was completed in 6 steps and of Carpatamides B and D in 7 steps, by employing the Wittig olefination, olefin cross metathesis and acid amine coupling reactions as key steps.

Four N,O‐Bidentate‐Chelated Ligand‐Tunable Copper(II) Complexes: Synthesis, Structural Characterization and Exceptional Catalytic Properties for Chan–Lam Coupling Reactions

AbstractFour N,O‐bidentate chelating ligands [L1=N‐(4‐thiazolylmethyl)morpholine‐N‐oxide, L2=N‐(2‐pyridylmethyl)pyrrolidine‐N‐oxide, L3=N‐(4‐thiazolylmethyl)pyrrolidine‐N‐oxide, and L4=N‐(2‐pyridylmethyl)morpholine‐N‐oxide] were designed and synthesized. The treatment of N,O‐bidentate ligands with CuCl2 in ethanol at room temperature afforded four new copper complexes—[Cu(L1)2]Cl2 (I), [Cu(L2)2][CuCl4] (II), [Cu(L3)2Cl]2[CuCl2(H2O)2]Cl2⋅10 H2O (III) and [Cu(L4)2][Cu(L4)2(CH3OH)2][CuCl4]2 (IV)—which were fully characterized by single‐crystal X‐ray diffraction, IR spectroscopy and elemental analyses. Most interestingly, the single‐crystal X‐ray diffraction analyses revealed that the N,O‐bidentate ligands L1–L4 can tune the corresponding geometry configuration of copper atoms in complexes I–IV. The copper atoms in I and II showed four‐coordinated distorted square planar geometry, whereas the central copper atom in III adopted a distorted square pyramidal geometry. It should be noted that complex IV was constructed by a distorted square planar CuN2O2 unit, one octahedral CuN2O4 unit and two [CuCl4]2− anions. Importantly, these copper(II) complexes, especially complex IV, showed high catalytic activity in Chan–Lam coupling reactions of primary or secondary amines with arylboronic acid under mild conditions. Substrates with many functional groups were tolerated and the C–N coupling products were afforded in good to excellent yields (up to 96 % yield).

Synthesis of Symmetric and Unsymmetric Secondary Amines from the Ligand-Promoted Ruthenium-Catalyzed Deaminative Coupling Reaction of Primary Amines.

The catalytic system generated in situ from the tetranuclear Ru-H complex with a catechol ligand (1/L1) was found to be effective for the direct deaminative coupling of two primary amines to form secondary amines. The catalyst 1/L1 was highly chemoselective for promoting the coupling of two different primary amines to afford unsymmetric secondary amines. The analogous coupling of aniline with primary amines formed aryl-substituted secondary amines. The treatment of aniline- d7 with 4-methoxybenzylamine led to the coupling product with significant deuterium incorporation on CH2 (18% D). The most pronounced carbon isotope effect was observed on the α-carbon of the product isolated from the coupling reaction of 4-methoxybenzylamine (C(1) = 1.015(2)). A Hammett plot was constructed from measuring the rates of the coupling reaction of 4-methoxyaniline with a series of para-substituted benzylamines 4-X-C6H4CH2NH2 (X = OMe, Me, H, F, CF3) (ρ = -0.79 ± 0.1). A plausible mechanistic scheme has been proposed for the coupling reaction on the basis of these results. The catalytic coupling method provides an operationally simple and chemoselective synthesis of secondary amine products without using any reactive reagents or forming wasteful byproducts.

Investigation the catalytic activity of nanofibrillated and nanobacterial cellulose sulfuric acid in synthesis of dihydropyrimidoquinolinetriones

Two novel types of nanocellulose-based catalyst, viz. nanofibrillated cellulose sulfuric acid (s-NFC) and nanobacterial cellulose sulfuric acid (s-BC), were prepared by a simple method and characterized by Fourier-transform infrared spectroscopy, transmission electron microscopy, field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction anlaysis, and nitrogen adsorption measurements. The catalytic activity of these two bio-based solid acid catalysts was examined in a one-pot, four-component coupling reaction of barbituric acid, dimedone, aryl aldehydes, and (hetero)aromatic amines in refluxing ethanol. The results confirmed that s-BC promoted the speed of the mentioned reaction more than s-NFC. The recovery and reusability of the degradable nanostructures showed that they could be used in at least three runs without loss of activity.

Design, Synthesis, and SAR of Novel 2-Glycinamide Cyclohexyl Sulfonamide Derivatives against Botrytis cinerea

N-(2-trifluoromethyl-4-chlorophenyl)-2-oxocyclohexyl sulfonamide (chesulfamide) is in the limelight as a novel fungicide, and has fungicidal activity against Botrytis cinerea. For exploring more novel structures, 33 new compounds were synthesized by N-alkylation and acid–amine coupling reactions with chesulfamide as the core moiety, and their structures were characterized and established by 1H-NMR, 13C-NMR, MS, and elemental analysis. The structure of (1R,2S)-2-(2-(N-(4-chloro-2-trifluoromethylphenyl)sulfamoyl)-cyclohexylamino)-N-(2-trifluoromethylphenyl) acetamide (II-19) was defined by X-ray single crystal diffraction. The in vivo and in vitro fungicidal activities against B. cinerea were evaluated. The bioassay results of mycelial growth demonstrated that most compounds exhibited excellent inhibitory activity against B. cinerea at 50 μg mL−1, and 7 compounds showed lower EC50 values than boscalid (EC50 = 4.46 μg mL−1) against B. cinerea (CY-09). In cucumber pot experiment, the inhibitory rates of four compounds (II-4, II-5, II-12, and II-13) against B. cinerea were 90.48, 93.45, 92.86, and 91.07, which were better than cyprodinil (88.69%), the best performing of all controls. In tomato pot experiment, the control efficacy of two analogs (II-8 and II-15) were 87.98 and 87.97% at 200 μg mL−1, which were significantly higher than boscalid (78.10%). Most compounds have an excellent fungicidal effect on B. cinerea, with potential as a lead compound for developing new pesticides.

Copper(II)‐Schiff Base Complex‐Functionalized Polyacrylonitrile Fiber as a Green Efficient Heterogeneous Catalyst for One‐Pot Multicomponent Syntheses of 1,2,3‐Triazoles and Propargylamines

AbstractA series of copper(II)‐Schiff bases‐functionalized polyacrylonitrile fiber catalysts were successfully prepared using copper acetate as copper source and characterized by elemental analysis, fourier‐transfer infrared spectroscopy, ultraviolet‐visible spectroscopy, X‐ray photoelectron spectroscopy and inductively coupled plasma analysis. Excellent physical strength and thermal stability of the fiber catalysts were demonstrated by scanning electron microscopy, X‐ray diffraction, thermogravimetric/differential scanning calorimetry analysis and mechanical strength measurements. Furthermore, these catalysts were successfully applied to one‐pot multicomponent copper‐catalyzed azide‐alkyne cycloaddition (CuAAC) reaction and aldehyde, alkyne, amine (A3) coupling reaction in which the influences of different substituent groups on the catalytic activities of fiber catalysts were investigated in detail. Among them, the bis[N‐ethyl‐3,5‐di‐tert‐butyl‐salicylideneiminato]copper(II)‐functionalized polyacrylonitrile fiber (PANS2F−Cu) as a green, efficient catalyst exhibited the best catalytic activity for its high hydrophobic micro‐environment can aggregate the reactants to the catalytic sites and accelerate the reaction. In addition, the PANS2F−Cu has performed well in scaled‐up experiment and shown excellent recyclability (at least ten times), and these enable it to have great potential for further applications.magnified image

Ordered mesoporous Au/TiO2 nanospheres for solvent-free visible-light-driven plasmonic oxidative coupling reactions of amines

Imines are important intermediates for the synthesis of fine chemicals and pharmaceuticals. Design of a “green” oxidation catalyst to promote the direct oxidation of amines to imines by dioxygen have attracted great attention. Herein, we designed a catalyst of ordered mesoporous Au/M-TiO2 nanoparticles using a template-based approach. The as-prepared Au/M-TiO2 nanoarrays of anatase crystalline structure, with high specific surface area (222 m2/g), small pore size (∼2.1 nm) and ordered arrangements, gave dense array of ultrasmall pore-confined gold nanoparticles. The mesoporous Au/M-TiO2 exhibits particularly high visible light activity for photocatalytic selective aerobic oxidation of benzylamine to N-benzylidene benzylamine in a green approach by utilizing dioxygen as an oxidant in solvent-free conditions. The yield of N-benzylidene benzylamine can reach 1.73 mmol (TOF = 178.6 h−1, based on Au) in Au/M-TiO2 system, which is 1.5 and 1.6 times higher than that of the Au/P25 and Au/Acros anatase photocatalysts, respectively. Furthermore, we can also achieve high yield of N-benzylidene benzylamine (1.30 mmol, TOF = 134.2 h−1, based on Au) in air atmosphere. The confinement effect of the mesopores in Au/M-TiO2 facilitate the formation of O2− radicals and make the bi-molecular reaction highly preferred for promoting the high selectivity and conversion in plasmonic photocatalysis. Meanwhile, the Au/M-TiO2 with mesoporous structure can facilitate the efficient contact between the solvent and the nanomaterial, while possessing sufficient interfacial area for active oxidation reactions. This work paves a promising way to develop visible light-responsive TiO2-based photocatalysts with high specific surface area for highly efficient green oxidative organic synthesis.

Efficient Synthesis of Propargylamines in Aqueous Media Catalyzed by Au Nanoparticles under Ambient Temperature

AbstractAn eco‐friendly gold‐based catalyst supported on proline decorated montmorillonite was synthesized. The catalyst was characterized by combination of Fourier‐transform infrared spectroscopy (FT‐IR), Field Emission Scanning Electron Microscopy (FE‐SEM), transmission electron microscopy (TEM), X‐ray diffraction (XRD), Brunauer–Emmett Teller (BET) surface area analysis, Ultraviolet–visible spectroscopy (UV‐Vis), Energy‐dispersive X‐ray spectroscopy (EDX), thermo gravimetric analysis (TGA) and atomic absorption spectroscopy (AAS) techniques. The synthesized catalyst was found to be a highly efficient heterogeneous nanocatalyst for multi component A3 coupling reaction of aldehyde, amine and alkyne in water as a green solvent at room temperature. This novel catalyst promotes multicomponent reaction of a large library of functional substrates under mild and sustainable conditions (water as a green solvent at ambient temperature). In addition, the catalyst could be easily recovered by simple filtration and reused for at least 6 cycles without losing its activity.

Highly Selective Rational Design of Peptide-Based Surface Plasmon Resonance Sensor for Direct Determination of 2,4,6-trinitrotoluene (TNT) Explosive

In this study, 2,4,6-trinitrotoluene (TNT) binding peptide was synthesized and screened for TNT specific detection using surface plasmon resonance (SPR) sensor. The TNT binding peptide was rational design and synthesized through amino acid sequence from complementarity determining region (CDR) in the anti-TNT monoclonal antibody, which was produced from hybridoma cell using TNP-KLH conjugate as antigen. Three TNT binding peptide sequences were obtained from the heavy chain of CDR1 named TNTHCDR1, TNTHCDR2 from CDR2 and TNTHCDR3 from CDR3 of anti-TNT antibody. Screening process of three candidate peptides were carried out by using the SPR sensor with direct determination, which the peptide was directly immobilized on the sensor chip CM7 surface through amine coupling reaction. The results demonstrated that peptide TNTHCDR3 was determined as TNT binding peptide and no non-specific binding was observed. The selectivity of TNT binding peptide TNTHCDR3 was also testified by six kinds of TNT analogues. The results indicated the specific binding between TNT and peptide TNTHCDR3.