Coupling Of Aryl Iodides Research Articles

Low-Valent Tungsten Catalyzed Carbonylative Synthesis of Benzoates from Aryl Iodides and Alcohols

Non-noble metals catalyzed carbonylative reactions serve as straightforward and sustainable methods for the synthesis of functionalized carbonyl-containing compounds. Herein, a low-valent-tungsten-catalyzed reaction that enables the coupling of aryl iodides and alcohols or phenols was disclosed, employing the readily available W(CO)6 as the effective catalyst and PPh3 as ligand. Under the optimal reaction conditions, aryl iodides smoothly underwent carbonylative coupling reactions with alcohols or phenols, processing the feature of broad substrate scope and good functional groups tolerance. Furthermore, this conversion can be carried out on a gram scale, showcasing significant promise in the synthesis of pharmaceutical or biologically active compounds.

Decarboxylative Cross-Coupling Enabled by Fe and Ni Metallaphotoredox Catalysis.

Decarboxylative cross-coupling of carboxylic acids and aryl halides has become a key transformation in organic synthesis to form C(sp2)-C(sp3) bonds. In this report, a base metal pairing between Fe and Ni has been developed with complementary reactivity to the well-established Ir and Ni metallaphotoredox reactions. Utilizing an inexpensive FeCl3 cocatalyst along with a pyridine carboxamidine Ni catalyst, a range of aryl iodides can be preferentially coupled to carboxylic acids over boronic acid esters, triflates, chlorides, and even bromides in high yields. Additionally, carboxylic acid derivatives containing heterocycles, N-protected amino acids, and protic functionality can be coupled in 23-96% yield with a range of sterically hindered, electron-rich, and electron-deficient aryl iodides. Preliminary catalytic and stoichiometric reactions support a mechanism in which Fe is responsible for the activation of carboxylic acid upon irradiation with light and a NiI alkyl intermediate is responsible for activation of the aryl iodide coupling partner followed by reductive elimination to generate product.

Triazine-wingtips accelerated NHC-Pd catalysed carbonylative Suzuki cross-coupling reaction

Triazine conjugated N-heterocyclic carbene palladium complexes were synthesized for reducing the Pd amount in the catalysts to the ppm levels. This work reports the carbonylative Suzuki-Miyaura coupling of aryl iodides catalyzed by N-heterocyclic carbenes palladium with triazine wingtips (T-NHC-Pd). More importantly, the palladacycles have been used to generate high turnover numbers (TON's) and turnover frequencies (TOF's).

Cross Coupling of Aryl Iodides with Terminal Alkynes, Catalyzed by a PdCl2–Hydrophilic Arylphosphine Ligand System

Cross Coupling of Aryl Iodides with Terminal Alkynes, Catalyzed by a PdCl2–Hydrophilic Arylphosphine Ligand System

Nickel-Catalyzed Reductive Arylation of α-Bromo Sulfoxide.

A nickel-catalyzed cross-electrophile coupling of aryl iodides with α-bromo sulfoxide to access a diverse array of aryl benzyl sulfoxides has been discovered. These reactions occurred under mild conditions with excellent functional group tolerance so that optically enriched sulfoxides could be coupled with aryl iodides, generating corresponding sulfoxides with excellent stereochemical integrity. Furthermore, the scalability of this transformation was demonstrated. Initial mechanistic studies revealed that the reaction undergoes a radical pathway.

A Green and Efficient Approach for Preparation of Diaryl Sulfones: Fe3O4@DABA-PA-CuBr2 Nanocomposite Catalyzed One-Pot Three-Component Aryl Iodides, Aryl Boronic Acids, and DABSO (as SO2 Source)

In this research work, Fe3O4@DABA-PA-CuBr2 nanocomposite was fabricated by a simple and inexpensive method by immobilizing copper(II) bromide on the surface of magnetic nanoparticles modified with 3,4-diaminobenzoic acid and picolinic acid. Deep eutectic solvents or DESs are green and environmentally friendly solvents that are used as catalyst or solvent in many reactions. The utilization of Fe3O4@DABA-PA-CuBr2 nanocatalyst in ChCl–Urea at 100 °C presented an attractive, environmentally benign and highly efficient catalytic system for the preparation of a broad range of diaryl sulfones through one-pot three-component coupling of aryl iodides, aryl boronic acids, and DABSO (as SO2 source). It should be noted that the Fe3O4@DABA-PA-CuBr2 catalyst was used several times without significant reduction of the catalytic activity. VSM, TEM, and ICP-OES analysis of the reused Fe3O4@DABA-PA-CuBr2 catalyst after eight cycles revealed that that the structure, magnetic property, shape, and size of the particles did not change significantly.

Sewage Sludge Activated Carbon as an Adsorbent and Catalytic Support: Evaluation of Nitrate Removal and Suzuki‐Miyaura Cross‐Coupling

AbstractThis manuscript reports the valorization of sewage sludge with the production of activated carbon. Thus, a series of 11 adsorbents are produced, activated with different substances (salt, acid, and base), and their adsorptive properties are carefully evaluated. The C6 series of activated carbons prove to be very efficient for removing nitrate anions from aqueous medium and, due to this, it is evaluated as a catalytic support for palladium nanoparticles. The generated solid, named Pd@CA6F, is the first report of a catalyst containing activated carbon from sewage sludge that is efficient in the Suzuki‐Miyaura cross‐coupling. The catalytic system developed is eco‐friendly, phosphine‐free, and of low cost. Good yields are obtained in the coupling of aryl iodides with phenylboronic acid in a short time. The same catalyst load could be recycled for up to ten times.

Reductive 1,2-Arylation of Isatins.

We report an intermolecular Ni-catalyzed reductive coupling of aryl iodides and isatins to form 3-hydroxyoxindoles. In contrast to common metal-mediated methods, sec-butanol is used as a mild stoichiometric reductant resulting in benign waste products. This formal 1,2-addition reaction is facilitated by a 1,5-diaza-3,7-diphosphacyclooctane (P2N2) ligand. Two Ni(0)-P2N2 species are prepared and found to be catalytically active, supporting a mechanistic hypothesis that this reaction proceeds by a modified carbonyl-Heck-type pathway.

A One-Pot Synthesis-Functionalization Strategy for Streamlined Access to 2,5-Disubstituted 1,3,4-Oxadiazoles from Carboxylic Acids.

A one-pot 1,3,4-oxadiazole synthesis-arylation strategy for accessing 2,5-disubstituted 1,3,4-oxadiazoles, from carboxylic acids, N-isocyaniminotriphenylphosphorane (NIITP), and aryl iodides, is reported. The reaction sequence, featuring a second stage copper-catalyzed 1,3,4-oxadiazole arylation, was found to tolerate (hetero)aryl, alkyl, and alkenyl carboxylic acids, and (hetero)aryl iodide coupling partners. The effectiveness of the two-stage strategy was exemplified by the late-stage functionalization of five carboxylic acid-containing APIs, and an extension to the synthesis of aminated 1,3,4-oxadiazoles using N-benzoyloxy amine coupling partners was also demonstrated.

C−I Selective Sonogashira and Heck Coupling Reactions Catalyzed by Aromatic Triangular Tri‐palladium

AbstractAromatic triangular tri‐palladium cations 1–3, abbreviated as [Pd3]+, have shown interesting photoelectric properties, Lewis basic character, and excellent activities in catalytic hydrogenation. Herein, we report the highly efficient and C−I selective Sonogashira and Heck coupling reactions catalyzed by these tri‐palladium complexes. Benefiting from the moderate C−I bond association energy, these tri‐palladiums presented exclusive reactivities to aryl iodides over the brominated aromatics in coupling reactions. In the Sonogashira pathway, good to excellent isolated yields (71–95 %) were achieved. Gram‐scale reaction reached 93 % of yield with palladium loading as few as 0.06 mol %. We also explored the electronic and steric effects for phenyl alkynes and aryl iodides including heteroaromatics like thiophene, pyridine, pyrazole, and pyrazine. Similarly, yields of 71–96 % were obtained for palladium loading of 1.5 mol% through catalyzed Heck coupling of aryl iodides and alkenes. The HRMS monitoring revealed that [Pd3]+ maintained as whole entity during the catalytic process due to its robusness.

Electric-field-induced coupling of aryl iodides with a nickel(0) complex.

The formation of carbon-carbon bonds with transition metal reagents serves as a cornerstone of organic synthesis. Here, we show that the reactivity of an otherwise kinetically inert transition metal complex can be induced by an external electric field to affect a coupling reaction. These results highlight the importance of electric field effects in reaction chemistry and offers a new strategy to modulate organometallic reactivity.

A Convenient Procedure for Sonogashira Reactions Using Propyne

AbstractA modified Sonogashira coupling of aryl iodides and propyne­ was achieved using only two equivalents of propyne in THF from –78 °C to room temperature.

Catalytic Aldehyde and Alcohol Arylation Reactions Facilitated by a 1,5-Diaza-3,7-diphosphacyclooctane Ligand.

We report a catalytic method to access secondary alcohols by the coupling of aryl iodides. Either aldehydes or alcohols can be used as reaction partners, making the transformation reductive or redox-neutral, respectively. The reaction is mediated by a Ni catalyst and a 1,5-diaza-3,7-diphosphacyclooctane. This P2N2 ligand, which has previously been unrecognized in cross-coupling and related reactions, was found to avoid deleterious aryl halide reduction pathways that dominate with more traditional phosphines and NHCs. An interrupted carbonyl-Heck type mechanism is proposed to be operative, with a key 1,2-insertion step forging the new C-C bond and forming a nickel alkoxide that may be turned over by an alcohol reductant. The same catalyst was also found to enable synthesis of ketone products from either aldehydes or alcohols, demonstrating control over the oxidation state of both the starting materials and products.

Regioirregular and catalytic Mizoroki–Heck reactions

The palladium-catalysed cross-coupling reaction between alkenes and aryl halides (the Mizoroki–Heck reaction) is a powerful methodology to construct new carbon–carbon bonds. However, the success of this reaction is in part hampered by an extremely marked regioselectivity on the double bond, which dictates that electron-poor alkenes react exclusively on the β-carbon. Here, we show that ligand-free, few-atom palladium clusters in solution catalyse the α-selective intramolecular Mizoroki–Heck coupling of iodoaryl cinnamates, and mechanistic studies support the formation of a sterically encumbered cinnamate–palladium cluster intermediate. Following this rationale, the α-selective intermolecular coupling of aryl iodides with styrenes is also achieved with palladium clusters encapsulated within fine-tuned and sterically restricted zeolite cavities to produce 1,1-bisarylethylenes, which are further engaged with aryl halides by a metal-free photoredox-catalysed coupling. These ligand-free methodologies significantly expand the chemical space of the Mizoroki–Heck coupling. The standard Mizoroki–Heck reaction of aryl halides usually makes electron-poor alkenes react exclusively on the β-carbon. Now, α-selective intramolecular and intermolecular versions of this reaction with electron-deficient alkenes are reported, giving access to otherwise difficult-to-synthesize products.

The synthesis of β-enaminones using trialkylamines and a Pd/DNA catalyst

A new one-pot procedure leading to β-enaminones has been developed. The elaborated methodology involves the cascade sequencing of carbonylative Sonogashira coupling of aryl iodide with a terminal alkyne and the oxidative dealkylation of tertiary amines. The efficient syntheses of β-enaminones were performed with a Pd/DNA catalyst, with NEt3, NPr3 and NBu3 used as amine sources. The catalyst was successfully recovered and used in several subsequent tests with the same results. The reaction mechanism, summarizing the activity of immobilized Pd NPs (palladium nanoparticles), was proposed.

New biomaterials for Ni biosorption turned into catalysts for Suzuki-Miyaura cross coupling of aryl iodides in green conditions.

In parallel with increasing Ni production and utilisation, Ni pollution in the soil–water continuum has become an alarming and global problem. Solutions for removing Ni from industrial effluents have been widely investigated and biosorption has emerged as an efficient, cost-effective, scalable and sustainable alternative for water treatment. However, the biosorption capacity is limited by the chemical composition of the biomaterial and the Ni-enriched biomaterials are rarely valorised. In this work, the biosorption capacity of three abundant biomaterials with different chemical properties – water hyacinth, coffee grounds and pinecones – was studied before and after functionalization, and reached a maximum biosorption capacity of 51 mg g−1 of Ni(ii). A bioinspired functionalization approach was investigated introducing carboxylate moieties and was conducted in green conditions. The Ni-enriched biomaterials were valorised by transformation into catalysts, which were characterised by MP-AES and XRPD. Their characterisation revealed a structure similar to nickel formate, and hence the Eco-Ni(HCOO)2 catalysts were tested in Suzuki–Miyaura reactions. Several aryl iodides were successfully cross-coupled to phenylboronic acids using Eco-Ni(HCOO)2 without any ligand, a mild and green base in a mixture of green solvents.

Formate-Mediated Cross-Electrophile Reductive Coupling of Aryl Iodides and Bromopyridines.

Two catalytic systems for the formate-mediated cross-electrophile reductive coupling of 4-iodoansiole with 6-bromopyridines are described. Using homogenous rhodium or heterogeneous palladium catalysts, the product of reductive biaryl cross-coupling could be formed in moderate yield with excellent levels of chemoselectivity.

Regioselective Synthesis of Polyfunctional Arenes by a 4-Component Catellani Reaction

Summary Polyfunctional arenes are an important part of the chemical value chain. To improve the efficiency of their synthesis, we have investigated a multicomponent approach built upon the Catellani platform. Here, we describe a 4-component coupling of aryl iodides lacking an ortho substituent that installs 3 discrete functional groups on the arene in a single step. The process is regio- and chemoselective and uncovers remote substituent effects that have a pronounced influence over intermediate Pd-(II) complexes. These intermediates have been a long-standing focus of the Catellani-reaction development, but persistent challenges have given rise to the well-known “ortho effect.” We now show that the ortho effect can be a positive element of reaction design, and that previously problematic iodides can now be used in complexity-generating transformations. In expanding the scope of the Catellani platform, we hope to provide mechanistic considerations to guide future reaction design, while also improving the environmental footprint of synthesizing polyfunctional arenes.

Recyclable heterogeneous palladium-catalyzed carbonylative Sonogashira coupling under CO gas-free conditions

A convenient, efficient and practical heterogeneous palladium-catalyzed carbonylative Sonogashira coupling of aryl iodides with terminal alkynes under CO gas-free conditions has been developed by using an MCM-41-supported bidentate phosphine palladium acetate complex as catalyst. Here, formic acid was used as the CO source with dicyclohexylcarbodiimide (DCC) as the activator and a wide variety of alkynyl ketones were generated in moderate to high yields. This heterogeneous palladium catalyst can be easily recovered via a simple filtration process and recycled up to 8 times without apparent loss of activity.

Green synthesis of graphene oxide (GO)-anchored Pd/Cu bimetallic nanoparticles using Ocimum sanctum as bio-reductant: an efficient heterogeneous catalyst for the Sonogashira cross-coupling reaction.

To explore the synergism between two metal centers we have synthesized graphene oxide (GO) supported Pd/Cu@GO, Pd@GO and Cu@GO nanoparticles through bio-reduction of Pd(NO3)2 and CuSO4·5H2O using Tulsi (Ocimum sanctum) leaf extract as the reducing and stabilizing agent. The graphene oxide (GO) was obtained by oxidation of graphite following a simplified Hummer's method. The as-prepared nanomaterials have been extensively characterized by FTIR, powder X-ray diffraction (PXRD), HRTEM, TEM-EDS, XPS, ICP-AES and BET surface area measurement techniques. The morphological study of Pd/Cu@GO revealed that crystalline bimetallic alloy type particles were dispersed on the GO layer. The activity of Pd@GO, Cu@GO and Pd/Cu@GO as catalysts for the Sonogashira cross-coupling reaction have been investigated and it was found that the Pd/Cu@GO nanostructure showed highly superior catalytic activity over its monometallic counterparts, substantiating the cooperative influence of the two metals. The inter-atom Pd/Cu transmetalation between surfaces was thought to be responsible for its synergistic activity. The catalyst showed higher selectivity towards coupling of aryl iodides with both aliphatic and aryl alkynes resulting in moderate to excellent isolated yield of the desired products (45–99%). The products have been characterized by GC-MS and 1H-NMR spectroscopic techniques and compared with authentic samples. The Pd/Cu@GO catalyst could be easily isolated from the reaction products and reused for up to at least ten successive runs effectively.