Oxidative Coupling Method Research Articles

Dinickel-Catalyzed N=N Coupling Reactions for the Synthesis of Hindered Azoarenes.

Azoarenes are the largest class of photoswitching molecules, and they have a broad range of applications in photopharmacology and materials science. Azoarenes possessing ortho-substitution often display improved properties, including isomerization under visible light irradiation, near-quantitative switching, and long thermal half-lives in the cis form. The synthesis of hindered ortho-substituted azoarenes is often low-yielding using established oxidative or reductive coupling methods. Here, we describe the design and synthesis of a new dinickel complex that catalyzes the dimerization of ortho-substituted aryl azides in high yield. Applications of this method in the synthesis of high-performance photoswitches, photoactive peptide cross-linkers, hindered diazocines, and main-chain azoarene polymers are described.

Synthesis of C2 symmetric hydroxylated biphenyls by microwave-assisted oxidative coupling of natural phenols

Phenolic compounds, abundant in various plants, exhibit a range of biological properties such as anti-inflammatory, antiseptic, and antioxidant activities. C2-symmetric biphenyl structures, present in many pharmacologically active substances, serve as fundamental backbones in many natural products, highlighting the significance of these compounds. This study introduces innovative microwave-assisted oxidative coupling methods for the synthesis of C2 hydroxylated biphenyls starting from thirteen natural phenols, focusing on eco-friendliness and efficiency. This approach aims to minimize environmental impact while emphasizing safety and sustainability by employing microwaves in environmentally sustainable solvents like water. The proposed mechanisms for the oxidative coupling of phenols include various possible reaction pathways, encompassing both homo and hetero radical-radical couplings.

Efficient Photocatalytic Selective Oxidation of Benzylamines over Cobalt Molecular Catalyst Covalently Bonded to Carboxyl Functionalized Carbon Nitride

Photocatalysis is accepted as a promising method for selective oxidative coupling of amine to imine. However, owing to the rapid dehydrogenation of the generated imine intermediate of α‐amino hydrogen to butyronitrile, it remains a huge challenge to fabricate an exquisite catalyst with enhanced conversion and selectivity. Herein, a novel heterogeneous catalyst (Bpy‐CoCl2/CNCOOH) is developed, where carboxyl functionalized carbon nitride (CNCOOH) serves as a substrate material and couples with highly efficient cobalt‐aminopyridine (Bpy‐CoCl2) molecular catalyst through covalent bonding. The catalyst not only effectively facilitates the transfer of photogenerated charges, but also generates mildly oxidatively active species of superoxide radicals, which can effectively oxidize various functionalized benzylamines to corresponding imines in the presence of oxygen with at least 78.5% conversion and >99% selectivity using O2 as oxygen source, especially for the unmodified benzylamine with >99% conversion and >99% selectivity. This unique combination of a selective molecular catalyst and a simple and robust semiconducting material open new avenues for the selective oxidative coupling of amines.

Visible-Light-Induced Oxidative Coupling of Phenols and Alkenylphenols with a Recyclable, Solid Photocatalyst.

A photocatalytic method for phenol and alkenylphenol oxidative coupling is reported using an inexpensive heterogeneous titanium dioxide photocatalyst with air and visible light. During the coupling process, the Ti-substrate complex is activated under visible light through a ligand to metal charge transfer effect, and the diphenol adduct is proposed to form through a radical cation. The heterogeneous TiO2 catalyst remains stable throughout the reaction and can be easily removed and reused multiple times.

Spectrophotometric Determination of Chlorpromazine HCl by Oxidative Coupling Method in Pharmaceutical formulations

The research includes the development of spectrophotometric method for determination microgram amounts of CPZ via oxidative coupling with the Sodium sulphacetamide reagent in presence of oxidizing agent potassium persulphate in the acidic medium (pH=1.8) to form a violet colored-dye, which is soluble in water and showed the highest intensity of absorption at λ max 550 nm. The method has been obeyed Beer's Law in the concentration range (2 - 20) µg/ml, with molar absorptivity of 1.2791 ×104 L/ mol. Cm, Sandel Index value 0.0278 µg/cm2. The detection limit 0.1727 µg/ml, with correlation coefficient 0.9983, the relative standard deviation of the method does not exceed 0.8933%, the proposed method was applied successfully for the determination of chlorpromazine hydrochloride in pharmaceutical preparation

Spectrophotometric determination of Folic acid (B9) by oxidative Coupling Reaction with 4-nitro-aniline

Development of an easy, inexpensive, fast and selective spectrophotometric method for the determination of Folic Acid (FA) by its reaction with 4-nitro aniline reagent, with good sensitivity, as an oxidative coupling method in the presence of Potassium permanganate solution, and it was found that the concentrations that were agreement with Beer-Lambert’s law at the wavelength of 374 nm ranged between 1- 21 µg/ml of folic acid solution, and a deviation from Beer’s law occurs at a concentration higher than 21 µg/mL, gave a linear coefficient and correlation coefficient its value is 0.9994, 0.9996, respectively, While the value of the molar absorption coefficient 12138.5 L/mol.cm and Sandel's sensitivity 0.0363 gm/cm2 with the limits of qualitative and quantitative detection 0.103 and 0.363 μg / ml-1, respectively. The proposed method was successfully applied for the determination of folic acid in its pharmaceutical preparations, from Erbil Company – Iraq. Trade name (folic acide).

Fabrication of Type II heterojunction in ZnIn2S4@ZnO photocatalyst for efficient oxidative coupling of Benzylamine under visible light

A series of ZnxInySz was synthesized by hydrothermal method, and the corresponding ZnxInySz@ZnO composites with the internal type II heterojunctions were prepared by solvent assisted interface. It could be observed in SEM and TEM images of ZnIn2S4@ZnO that ZnIn2S4 present a petal-like sphere composed ofnanosheets with nano-fragments of ZnO attached on its surface. The results offluorescence spectra and electrochemical impedance spectroscopy indicated that theformation of type II heterojunctions within ZnIn2S4@ZnO composites significantly promotedthe separation of photocarriers. Therefore, ZnIn2S4@ZnO delivered excellent catalyticperformance for oxidative coupling of benzylamine. Under visible-light irradiation of 2 h, the conversion of benzylamine is as high as 96%, and the catalytic performance is still very steady after several cycles. It has not been reported that such a high conversion can be achieved in such a short period of time. Another advantage is that the coupling reaction does not require additional oxygen atmosphere and can be carried out in air condition, endowing this process with the feature of easier to be operated. This work provids an effective method for oxidative coupling of benzylamine through environmentally friendly way.This work provided an effective method for coupling of benzylamine environmentally friendly way.

Preparation of LaAlO3 perovskite catalysts by simple solid-state method for oxidative coupling of methane

Abstract The preparation of LaAlO3 perovskite catalysts for the oxidative coupling of methane (OCM) using a very simple solid-state method with good reproducibility is described. To obtain high performance LaAlO3 catalysts, preparation conditions such as time, temperature, and oxygen content, which have a strong effect on the catalytic activity, are controlled during the calcination process. As the calcination time and temperature increase, the catalytic activity of LaAlO3 improves due to the good homogeneity and high crystallinity of LaAlO3 perovskite. Especially, the LaAlO3 catalyst calcined at 1350 °C for 24 h shows the highest selectivity and yield of C2 hydrocarbons. LaAlO3 catalysts calcined at various oxygen fractions show a volcano-shaped curve with respect to oxygen content in calcination gas, and the LaAlO3 catalyst prepared with an oxygen content of 5 % exhibits the best catalytic performance in this reaction. The appropriate oxygen fraction provides the LaAlO3 catalyst with a large amount of electrophilic lattice oxygen species and a sufficient amount of adsorption oxygen species, which are known to play key roles in the OCM reaction. This study clearly reveals this simple, highly reproducible, and mass-productive solid-state method as a promising preparation method for high performance LaAlO3 perovskite catalysts for OCM.

Oligothiophene Synthesis by a General C–H Activation Mechanism: Electrophilic Concerted Metalation–Deprotonation (eCMD)

Oxidative C-H/C-H coupling is a promising synthetic route for the streamlined construction of conjugated organic materials for optoelectronic applications. Broader adoption of these methods is nevertheless hindered by the need for catalysts that excel in forging core semiconductor motifs, such as ubiquitous oligothiophenes, with high efficiency in the absence of metal reagents. We report a (thioether)Pd-catalyzed oxidative coupling method for the rapid assembly of both privileged oligothiophenes and challenging hindered cases, even at low catalyst loading under Ag- and Cu-free conditions. A combined experimental and computational mechanistic study was undertaken to understand how a simple thioether ligand, MeS(CH2)3SO3Na, leads to such potent reactivity toward electron-rich substrates. The consensus from these data is that a concerted, base-assisted C-H cleavage transition state is operative, but thioether coordination to Pd is associated with decreased synchronicity (bond formation exceeding bond breaking) versus the "standard" concerted metalation-deprotonation (CMD) model that was formalized by Fagnou in direct arylation reaction. Enhanced positive charge build-up on the substrate results from this perturbation, which rationalizes experimental trends strongly favoring π-basic sites. The term electrophilic CMD (eCMD) is introduced to distinguish this mechanism from the standard model, even though both mechanisms locate in a broad concerted continuum. More O'Ferrall-Jencks analysis further suggests eCMD should be a general mechanism manifested by many metal complexes. A preliminary classification of complexes into those favoring eCMD or standard CMD is proposed, which should be informative for studies toward tunable catalyst-controlled reactivity.

Cetyltrimethyl ammonium bromide catalysed oxidative cross dehydrogenative coupling of benzylic C(sp3)-H bonds in methylarenes with P(O)-OH compounds.

An efficient metal-free method for the synthesis of organophosphorus compounds via oxidative cross dehydrogenative coupling of benzylic C(sp3)-H bonds in methylarenes with P(O)-OH compounds catalysed by cetyltrimethyl ammonium bromide (CTAB) is reported. Various methylarenes and P(O)-OH compounds are tolerated in the reaction with moderate to good yields. Compared to previous studies, the present study extends the substrate scope and adopts a new reaction system of an ammonium salt catalyst (CTAB) and an oxidant (DTBP). The results of control and mechanistic experiments are generally in agreement with the overall proposed pathway. This method circumvents the use of toxic P-halogen reagents and P(O)-H compounds for the synthesis of organophosphorus compounds.

Probing the real-time photocatalytic activity of CdS QDs sensitized conducting polymers: Featured PTh, PPy and PANI

In the present work, we first synthesized widely used conducting polymers like polythiophene (PTh), polypyrrole (PPy) and polyaniline (PANI) by oxidative coupling method. Later, we have in-situ grown cadmium sulfide (CdS) quantum dots (QDs) in presence of these conducting polymers to form CdS/polythiophene (CdS/PTh), CdS/polypyrrole (CdS/PPy) and CdS/polyaniline (CdS/PANI) hybrid nanocomposites. All characterization techniques confirm the formation of hybrid nanocomposites while also highlights the interaction of CdS with conducting polymers. Thereafter, as synthesized conducting polymers and their hybrid nanocomposites were employed as photocatalyst for degradation of methylene blue (MB) dye under direct sun light (light intensity = 75000–90000 Lux). Here, CdS plays a key role to enhance the photocatalytic activity of overall composite due to effective charge transfer with these conducting polymers. The in-depth comparative study of photocatalytic activity was performed for these hybrid nanocomposites and the effectiveness with respect to stability is reported. The role of CdS QDs as sensitizer is proposed on the basis of synergetic effect between CdS and PTh, PPy or PANI polymers.

The effect of Argon pressure dependent V thin film on the phase transition process of (020) VO2 thin film

Abstract It has been proved challenging to fabricate the single crystal orientation of VO 2 thin film by a simple method. Based on chemical reaction thermodynamic and crystallization analysis theory, combined with our experimental results, we find out that when stoichiometric number of metallic V in the chemical equation is the same, the ratio of metallic V thin film surface average roughness R a to thin film average particle diameter d decreases with the decreasing sputtering Argon pressure. Meanwhile, the oxidation reaction equilibrium constant K also decreases, which will lead to the increases of oxidation time, thereby the crystal orientation of the VO 2 thin film will also become more uniform. By sputtering oxidation coupling method, metallic V thin film is deposited on c-sapphire substrate at 1 × 10 −1 Pa, and then oxidized in the air with the maximum oxidation time of 65s, high oriented (020) VO 2 thin film has been fabricated successfully, which exhibits ∼4.6 orders sheet resistance change across the metal-insulator transition.

P‐169: Solution‐processed Organic Light‐emitting Diodes with a Polymeric Hole Transport Layer Crosslinked by Surface Initiated Oxidative Crosslinking

A surface initiated oxidative coupling method of a carbazole compound was used as a fabrication approach of a crosslinked hole transport layer for solution processed organic light‐emitting diodes. The surface initiated oxidative coupling method was able to avoid damage by the organic solvent in the manufacturing process. Moreover, the hole transport material was able to prevent exciton quenching by the oxidizing agent and solved the problem of luminous efficiency reduction of the organic light emitting device because the oxidant was not in contact with the emitting layer. As a result, the surface initiated oxidative crosslinking method improved the luminous efficiency and lifetime characteristics of the solution processed organic light‐emitting devices.

TEMPO‐Catalyzed Aerobic Oxidative Coupling of Thiols for Metal‐Free Formation of S−N/S−S Bonds

AbstractCatalytic syntheses of organic sulfenamides and disulfides have great significance and value in synthetic chemistry and bioscience. To establish a versatile and efficient technology for such reactions, an aerobic oxidative coupling method for the formation of S−N and S−S bonds, using TEMPO as a catalyst and O2 as an oxidant, has been successfully developed. Reactions showed good tolerance toward various amines and thiols. Sulfenamides were produced in up to 99 % yield, while disulfides were formed in up to 97 % yield in one‐pot syntheses. Activation of the N−H bond by 2,2‐disbenzothiazoledisulfide showed the great potential in organic synthesis.

Surface initiated oxidative crosslinking of a polymeric hole transport material for improved efficiency and lifetime in soluble organic light-emitting diodes

A surface initiated oxidative coupling method was developed as a crosslinking approach of hole transport materials for solution processed organic light-emitting diodes. The surface initiated crosslinking method was better than bulk oxidative crosslinking method in terms of quantum efficiency and lifetime of the organic light-emitting diodes by suppressing exciton quenching by the hole transport layer. Doubled efficiency and quadrupled lifetime were obtained using the new crosslinking approach without any chemical modification of the hole transport material.

Tuning the singlet-triplet energy splitting by fluorination at 3,6 positions of the 1,4-biscarbazoylbenzene

While it has been known in the past decades that fluorination induces stability and electron transporting ability, less is known is the effect of fluorination on singlet-triplet energy splitting. A series of carbazole derivatives with fluorination at the 3 and/or 6 positions are synthesized using oxidative biaryl coupling method. It was found that fluorine at the 3 and/or 6 positions of 1,4-biscarbazoylbenzene (CCP) reduces the singlet energies and lowers the Lowest Unoccupied Molecular (LUMO) level compared to the non-substituted molecules The triplet energies are almost unaffected by the fluorination. This is in contrast with tert-butyl substituents where the triplet energies are reduced. Density functional theory is used to examine the frontier molecular orbitals. It was found that fluorination of carbazole at 3 and/or 6 positions increase the effective conjugation as a result of mesometric effect while tert-butyl substituents lower the bandgap through hyperconjugation. Fluorination of carbazole at 3 and 6 positions strongly depleted the connecting benzene of electrons at the LUMO levels. This gives rise to partial spatial separation of the highest occupied molecular orbital (HOMO) and the LUMO levels in fluorinated CCP which reduces the singlet-triplet energy splitting.

Controlled Shape and Nucleation Switching of Interfacially Polymerizable Nanoassemblies by Methyl Substitution

Interfacial polymerization of uniform template-free nanostructures is very challenging since many factors play determinant roles in the final structure of the resulting nanoassemblies. Here, we present a single oxidative coupling method for the synthesis of different nanoshapes by addition or substitution of a methyl group on aniline monomers to freely alter the mechanism of monomer-to-polymer conversion. Well-defined nanotubes, nanohollows, and solid nanospheres are obtained from aniline, N-methylaniline, and 2-methylaniline polymerizations, respectively. We found that the extent of hydrophobicity and protonation under mild acidic conditions determines the monomers’ arrangement in micelle or droplet form, reactivity, and nucleation mechanism. These can subsequently affect the final morphology through a fusion process to form tubular structures, external flux of monomers to form nanohollows, and intradroplet oxidation to form solid nanospheres. Altered biological responses, such as cytocompatibility, redo...

Metal-Free Difunctionalization of Alkynes with 2-Chlorodithiane for Synthesis of β-Ketodithianes.

Dithianes are versatile umpolung intermediates in organic synthesis but have rarely been employed in radical cross-coupling reactions. Here we describe the oxidative coupling method for alkyne difunctionalization under metal-catalyst-free conditions. The efficient protocol directly affords a variety of β-ketodithianes in good to excellent yields with high regioselectivities. It provides a general pathway for accessing valuable dithianes with controlled formation of a new C-C bond and a C-O bond via a radical coupling pathway.

Copper-catalyzed arenes amination with saccharins

A novel copper-catalyzed direct C-N formation reaction of simple arenes with cheap and pharmacological saccharin derivatives under relatively mild conditions was developed with arenes as limiting reagents. This work provided a new method for oxidative coupling of aromatic C(sp2)-H bonds and N-H bonds.

An oxygen permeable membrane microreactor with an in-situ deposited Bi1.5Y0.3Sm0.2O3−δ catalyst for oxidative coupling of methane

In this study, a novel catalytic hollow fibre membrane microreactor (CHFMMR) was developed using a micro-structured La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) hollow fibre as an oxygen separation membrane as well as a functional substrate for in-situ deposition of a Bi1.5Y0.3Sm0.2O3−δ (BYS) catalyst using a sol–gel method for oxidative coupling of methane (OCM) reaction. A nano-thickness BYS catalytic layer (300–500nm) was successfully deposited onto the microchannel walls throughout the whole hollow fibre. The differences in the OCM performances between the in-situ sol–gel prepared CHFMMR and a washcoat CHFMMR are highlighted. The performance of such CHFMMR is found to be strongly dependent on the properties of BYS and the reaction conditions. When the particle size of BYS was reduced to nano-sizes and was uniformly dispersed, the performance of such CHFMMRs changes drastically, in which higher oxygen permeation rate and methane conversion were obtained. A decrease in residence time was observed to give a better C2+ selectivity and C2+ yield, achieving a maximum value of 79% and 39%, respectively at 900°C. To the best of our knowledge, the C2+ yield obtained in this study is the highest value reported so far. The C2+ productivity rate of the in-situ design CHFMMR was observed to be nearly four times higher than that of the washcoat CHFMMR due to the better accessibility of reactants towards lattice/active site of the uniform BYS catalytic layer.