Copper-free Sonogashira Coupling Reaction Research Articles

Retraction: Bis-salophen palladium complex immobilized on Fe3O4@SiO2 nanoparticles as a highly active and durable phosphine-free catalyst for Heck and copper-free Sonogashira coupling reactions.

Retraction of 'Bis-salophen palladium complex immobilized on Fe3O4@SiO2 nanoparticles as a highly active and durable phosphine-free catalyst for Heck and copper-free Sonogashira coupling reactions' by Ali Reza Sardarian et al., Dalton Trans., 2019, 48, 3132-3145, https://doi.org/10.1039/C9DT00060G.

Palladium-Catalyzed Mizoroki-Heck and Copper-Free Sonogashira Coupling Reactions in Water Using Thermoresponsive Polymer Micelles.

A few kinds of thermoresponsive diblock copolymers have been synthesized and utilized for palladium-catalyzed coupling reactions in water. Poly(N-isopropylacrylamide) (PNIPAAm) and poly(N,N-diethylacrylamide) (PDEAAm) are employed for thermoresponsive segments and poly(sodium 4-styrenesulfonate) (PSSNa) and poly(sodium 2-acrylamido-methylpropanesulfonate) (PAMPSNa) are employed for hydrophilic segments. Palladium-catalyzed Mizoroki–Heck reactions are performed in water and the efficiency of the extraction process is studied. More efficient extraction was observed for the PDEAAm copolymers when compared with the PNIPAAm copolymers and conventional surfactants. In the study of the Sonogashira coupling reactions in water, aggregative precipitation of the products was observed. Washing the precipitate with water gave the product with satisfactory purity with a good yield.

Immobilized Pd on a NHC-functionalized metal-organic FrameworkMIL-101(Cr): An efficient heterogeneous catalyst in the heck and copper-free Sonogashira coupling reactions

A heterogeneous palladium catalyst system based on immobilization of palladium moieties on a N-heterocyclic carbene (NHC) modified metal organic framework (MOF) was developed for the Heck and copper-free Sonogashira coupling reactions. In order to prepare this catalyst system, first, MIL-101(Cr) was functionalized with NHC moieties through a post synthetic modification (PSM) approach, and then Pd metal was stabilized on the prepered MIL-101(Cr)-NHC substrate. This material was characterized using various microscopic and spectroscopic techniques and then was used as an efficient heterogeneous Pd catalyst system in the Heck and copper-free Sonogashira reactions. Results of the heterogeneity tests showed that the Pd-NHC-MIL-101(Cr) catalyst can efficiently catalyzed these coupling reactions heterogeneously and no remarkable changes observed in the morphology and structure of MIL-101(Cr) template during the reaction progress. Also, existence of palladium nanoparticles immobilized on the MOF structure affirmed by the TEM and XPS analysis confirmed the oxidation state of Pd. A variety of alkene and alkyne derivatives were synthesized in good to excellent yields using this heterogeneous Pd catalyst system under normal conditions. More importantly Pd-NHC-MIL-101(Cr) catalyst was simply recovered from the reaction medium without remarkable decreasing in its catalytic activities after five times of reusability. The ICP analysis showed the very low Pd and Cr metals leaching, representing high stability and applicability of this catalyst in Pd coupling reactions.

Palladium anchored on guanidine-terminated magnetic dendrimer (G3-Gu-Pd): An efficient nano-sized catalyst for phosphorous-free Mizoroki-Heck and copper-free Sonogashira couplings in water

In this research, a novel type of Fe3O4@silica-supported dendrimer capped by guanidine groups for immobilization of palladium was reported. This novel nano-sized catalyst was characterized by FTIR, TGA, XRD, FESEM, EDX, VSM, XPS and HRTEM methods. Enhanced catalytic activity of the prepared catalyst in Mizoroki-Heck and copper-free Sonogashira coupling reactions were evaluated in water as a green solvent. The influence of the various reaction parameters such as catalyst dosage, time and temperature on two mentioned C–C coupling reactions were studied. Results showed that the catalyst could be easily recovered by simple separation by an external magnet and reused for five cycles of recovery without considerable losing of its activity.

Bis-salophen palladium complex immobilized on Fe3O4@SiO2 nanoparticles as a highly active and durable phosphine-free catalyst for Heck and copper-free Sonogashira coupling reactions.

New Fe3O4@SiO2 core-shell superparamagnetic nanoparticles functionalized by a bis-salophen Schiff base Pd complex were synthesized and employed as an efficient magnetic nanocatalyst in the Heck and Sonogashira cross coupling reactions. The synthesized nanostructures were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), dynamic light scattering (DLS), energy dispersive X-ray analysis (EDX), X-ray photoelectron spectroscopy (XPS), elemental analysis (CHN), cyclic voltammetry (CV), Brunauer-Emmett-Teller analysis (BET), and UV-vis spectroscopy. The morphology and size of the nanoparticles were investigated by FE-SEM and TEM analyses. Furthermore, the magnetic properties of the catalyst were investigated by VSM analysis. The loading content and leaching amounts of palladium on the catalyst were measured by inductively coupled plasma (ICP) analysis. Also, the thermal behavior of this magnetic heterogeneous catalyst was studied using a TGA instrument. This heterogeneous catalytic system showed a good performance in the coupling of aryl halides with alkynes (Sonogashira reaction) as well as aryl halides with alkene derivatives (Heck reaction). High to excellent yields were achieved for these C-C coupling reactions. The catalyst can be simply separated from the reaction media by an external magnet and reused for eight consecutive runs without any significant loss of activity. Finally, the kinetics of the reactions were studied in this work.

Correction to: Novel one-pot synthesis of 1-alkyl-2-(aryloxy)methyl-1H-pyrrolo[2,3-b]quinoxalines via copper-free Sonogashira coupling reaction

A novel, simple, and efficient protocol is described for the synthesis of 1-alkyl-2-(aryloxy)methyl-1H-pyrrolo[2,3-b]quinoxalines via the one-pot reaction of phenol or 2-naphthol derivatives, propargyl bromide, and N-alkyl-3-chloroquinoxaline-2-amines in the presence of palladium catalyst. This one-pot reaction is carried out in the absence of any copper salt at room temperature. The reaction product is dependent on the nature of the base used. The use of morpholine, as the base, affords the final cyclized product, and triethylamine only gives the coupling product.

Tetradentate Palladium(II) Salophen Complexes: Synthesis, Characterization and Catalytic Activities in Copper-Free Sonogashira Coupling Reaction

This paper reports the synthesis and characterization of three salophen ligands; 2,2'-((1E,1'E)-(1,2 phenylenebis(azanylylidene))bis(methanylylidene))diphenol [L1H], 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis (methanylylidene))bis(4-chlorophenol) [L1C] and 2,2'-((1E,1'E)-(1,2-phenylenebis(azanylylidene))bis(methanylylidene))bis(4-methoxylphenol) [L1OME]. The compounds were prepared from condensation reaction between salicylaldehyde, and its derivatives, with ortho-phenylenediamine. Their palladium(II) complexes, namely PdL1H, PdL1C and PdL1OME were synthesized through insertion reaction between the ligands with palladium(II) acetate. All compounds were characterized through melting point, elemental analysis, infrared spectroscopy, 1H and 13C NMR spectroscopy. Palladium(II) complexes were tested as homogenous catalysts in copper-free Sonogashira coupling reaction between iodobenzene and phenylacetylene in DMSO using triethylamine as base with 1.0 mmol% catalyst loading. The most performing catalyst was PdL1OME with 91% conversion followed by PdL1H (83%) and PdL1C (27%).

Pd(0) nanoparticle immobilized on cyclodextrin-nanosponge-decorated Fe 2 O 3 @SiO 2 core-shell hollow sphere: An efficient catalyst for C C coupling reactions

Abstract Amine-functionalized core-shell Fe2O3 hollow spheres (h-Fe2O3@SiO2 N) were decorated with Cl-functionalized cyclodextrin nanosponge, CDNS-Cl, covalently. The resulting hybrid system, h-Fe2O3@SiO2 CDNS, was then used as a magnetically separable support for immobilization of Pd(0) nanoparticles, derived from a bio-based approach. The obtained catalyst, Pd@h-Fe2O3@SiO2 CDNS, was characterized by using SEM/EDS, TEM, XRD, BET, ICP-AES, FTIR, TGA and VSM. Moreover, the catalytic activity of Pd@h-Fe2O3@SiO2 CDNS was confirmed for ligand and copper-free Heck and Sonogashira coupling reactions in aqueous media. Comparison of the catalytic activity of the Pd@h-Fe2O3@SiO2 CDNS and Pd@h-Fe2O3@SiO2, established superior catalytic activity of former indicating the role of CDNS in catalysis. Furthermore, the catalytic activity and recyclability of Pd@h-Fe2O3@SiO2 CDNS was higher than that of Pd@CDNS. The catalyst could be successfully recycled for several consecutive reaction times with slight loss of the catalytic activity. The ICP-AES analysis confirmed that the leaching of Pd nanoparticles was negligible upon each reaction cycle.

Pd@HNTs-CDNS-g-C3N4: A novel heterogeneous catalyst for promoting ligand and copper-free Sonogashira and Heck coupling reactions, benefits from halloysite and cyclodextrin chemistry and g-C3N4 contribution to suppress Pd leaching

For the first time, a ternary hybrid system composed of halloysite nanotubes, HNTs, cyclodextrin nanosponges, CDNS, and g-C3N4 is prepared and used for immobilization of Pd(0) nanoparticles and development of a heterogeneous catalyst, Pd@HNTs-CDNS-g-C3N4 for promoting ligand and copper-free Sonogashira and Heck coupling reactions in aqueous media. HNT as a porous tubular clay with outstanding thermal, mechanical and textural properties can act as a support for immobilizing Pd nanoparticles. The role of CDNS can be explained on the base of its capability to form inclusion complexe with substrates and bringing them in the vicinity of the catalytic active sites. Regarding the role of g-C3N4 in catalysis, it is proved that its presence can suppress the Pd leaching dramatically. The contribution of each component as well as synergistic effect between them results in high catalytic activity and recyclability (up to 10 reaction runs) of the catalyst.

Combination of carbon nanotube and cyclodextrin nanosponge chemistry to develop a heterogeneous Pd-based catalyst for ligand and copper free C-C coupling reactions

Carbon nanotubes and cyclodextrin nanosponge were hybridized and used as a support for embedding Pd(0) nanoparticles and developing a novel and heterogeneous catalyst, Pd@CDNS-CNT, for promoting ligand and copper-free Sonogashira and Heck coupling reactions in aqueous media and mild reaction condition. Cyclodextrin nanosponge could contribute to catalysis through encapsulating the reagents and transferring them in the vicinity of Pd nanoparticles. The results established that the catalytic activity of Pd@CDNS-CNT was superior to those of Pd@CNT, Pd@CDNS and Pd@CNT + CDNS, indicating the synergism between the components of the hybrid system. Notably, various aryl halides including aryl iodide, bromide and chloride were useful substrates for the coupling reactions and affording the corresponding products in high to excellent yields in short reaction times. Moreover, the catalyst was recyclable up to six reaction runs with negligible Pd leaching.

Phosphine and Copper-free Sonogashira coupling reaction catalyzed by lignin supported palladium nanoparticles

Lignin supported palladium nanoparticles (lignin@Pd-NPs) with an average size of 1–5 nm synthesized by green procedure was successfully explored in phosphine and copper-free Sonogashira C-C coupling reaction of various aryl halides with phenyl acetylene under aerobic conditions. It was found that the catalyst exhibited a high activity resulting desired products in 90-95 % yields. The catalyst was heterogeneous and was recovered by filtration and then recycled up to 3 consecutive reactions of the iodobenzene and phenyl acetylene under similar conditions resulting 93 to 88 % yields of diphenylacetylene.

Ternary hybrid system of halloysite nanotubes, polyacrylamides and cyclodextrin: an efficient support for immobilization of Pd nanoparticles for catalyzing coupling reaction

Abstract Taking advantage of the properties of polyacrylamide (P), the capability of cyclodextrin (CD) to form inclusion complex and outstanding features of halloysite nanoclay as catalyst support, a ternary hybrid system, Hal-P-CD, was designed and synthesized through growing polyacrylamide on the surface of functionalized halloysite nanotubes followed by introduction of β-cyclodextrin. The hybrid system was successfully used for immobilization of Pd nanoparticles and formation of a heterogeneous catalyst, Pd@Hal-P-CD. The structure of Pd@ Hal-P-CD was confirmed by using SEM/EDS, TEM, XRD, BET, ICP-AES, TGA, FTIR and elemental mapping analysis and its catalytic activity was studied for promoting ligand and copper-free Sonogashira coupling reaction in aqueous media (1:1 mixture of water and ethanol). The results established that Pd@Hal-P-CD could catalyze the coupling reaction to afford the desired products in high yields and short reaction times. Notably, the catalytic activity of Pd@Hal-P-CD was superior to those of Pd@Hal-P and Pd@Hal. The study of the reusability of the catalyst up to 7 reaction runs as well as Pd leaching confirmed the heterogeneous nature of the catalysis and the efficiency of Hal-P-CD for suppressing the Pd leaching. Additionally, this catalyst could also be successfully used for promoting Heck coupling reaction.

Synthesis of Internal Alkynes through an Effective Tandem ­Elimination–Hydrodebromination–Cross-Coupling of gem-­Dibromoalkenes with Halobenzenes

Carbon–carbon couplings are among the most important strategies for constructing functional molecules in organic synthetic chemistry, and cheap, diverse, and readily available coupling partners are crucial to these diverse reactions. In this contribution, we report the first palladium-catalyzed C–C cross-coupling reaction of two kinds of organic halide, a gem-dibromoalkene and a halobenzene, as the starting materials. Terminal alkynes were generated in situ through a tandem elimination–hydrodebromination process, and the internal alkyne final products were synthesized in one pot. The reaction proceeded under simple, facile, and classic copper-free Sonogashira coupling reaction conditions in good to excellent yields.

ONO pincer type binuclear Pd(II) complex: Synthesis, crystal structure and catalytic utilization of the resulting organopalladium complex in catalytic copper-free Sonogashira coupling reaction

New binuclear palladium (II) complex featuring ONO pincer type hydrazone ligand was synthesized and characterized by spectroscopic and single-crystal XRD analysis. This complex showed excellent catalytic activity towards the copper-free Sonogashira cross coupling reaction. The main advantages over previous methodologies include low catalyst loading, less problematic reaction media (H2O–DMSO) and reusability in homogenous systems for optimal performance.

Novel phthalocyanine–BODIPY conjugates and their photophysical and photochemical properties

Novel zinc(II) phthalocyanines bearing boron dipyrromethene (BODIPY) (8) and its mono-styryl (9) and di-styryl (10) derivatives containing p-(N,N-diethylamino)benzaldehyde moieties were designed and synthesized for the first time. These phthalocyanines (8–10) were prepared by the copper-free Sonogashira coupling reaction of terminal ethynyl functionalized BODIPYs [4,4′-difluoro-8-(4-propynyloxy)-phenyl-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (2), 4,4′-difluoro-8-(4-propynyloxy)-phenyl-3,5,7-trimethyl-1-((4-diethylaminophenyl)ethenyl)-4-bora-3a,4a-diaza-s-indacene (5), or 4,4′-difluoro-8-(4-propynyloxy)-phenyl-3,5-dimethyl-1,7-bis((4-4″-diethylaminophenyl)ethenyl)-4-bora-3a,4a-diaza-s-indacene (6)] with tetrakis(iodo) zinc(II) phthalocyanine (7). All newly synthesized compounds were fully characterized by elemental analysis and general spectroscopic methods such as 1H NMR, FT-IR, mass, UV–Vis, and fluorescence. The photophysical (fluorescence quantum yields and lifetimes), photochemical (singlet oxygen generation capability and photodegradation behaviors) properties of these phthalocyanines were also investigated for determination of their photodynamic therapy (PDT). The results obtained indicated that these conjugates could be promising photosensitizers for PDT applications.

Copper-free Sonogashira reactions catalyzed by a palladium(II) complex bearing pyrenealdehyde thiosemicarbazonate under ambient conditions

Convenient synthesis of a new square-planar mononuclear palladium(II) complex bearing N,S-donor 1-pyrenaldehyde 4-methyl-3-thiosemicarbazonate (L−) as ligand is described. The identity of the complex has been established as [Pd(L)Cl(PPh3)] by elemental analysis, ESI-MS, FT-IR, NMR and single crystal X-ray crystallographic measurements. The complex has been found to be an active and efficient homogeneous catalyst for the copper free Sonogashira coupling reactions of phenylacetylene with various aryl halides (bromides and chlorides) at room temperature under aerobic conditions.

Synthesis, structural characterization and in vitro anti-cancer activity of functionalized N-heterocyclic carbene platinum and palladium complexes

A series of platinum(II) and palladium(II) complexes bearing N-heterocyclic carbene ligands functionalized by specific functionalities such as alcohol, nitrile or ester were synthesized. The novel complexes were fully characterized and X-ray diffraction was used for the structure determination of eight derivatives. The reactivity of the functional groups has been studied; for example, Pt and Pd NHC complexes containing tBu ester functions were easily hydrolyzed giving water-soluble NHC complexes. The palladium complex 21 containing dangling COOH group was evaluated in copper-free Sonogashira coupling reaction. In addition, platinum NHC complexes are attractive metal-based systems for the development of anticancer drugs. Preliminary results of the biological effects on various human cancer and non-cancer cells are also reported.

Effective palladium(II)-bis(oxazoline) catalysts: synthesis, crystal structure, and catalytic coupling reactions

New bis(oxazoline) ligands and their palladium complexes were synthesized and characterized. X-ray crystal structures of the two new complexes showed distorted square planar geometry with the palladium ion bonded to nitrogens of two bidentate heterocycles in addition to two bromides and two acetate ions for Pd-BOX-1 and Pd-BOX-2, respectively. The complexes adopt a chair structure with a rigid curvature inducing an inherent chirality. The complexes were effective catalysts for Suzuki–Miyaura, Mizoroki–Heck, and copper-free Sonogashira coupling reactions in aqueous dimethylformamide and under aerobic conditions. The reaction conditions were optimized for best solvent, base, and temperature. The substrate scope of the new catalytic system was evaluated for coupling reactions of a variety of aryl halides with aryl boronic acids, alkenes, and alkynes.

Green synthesis of Pd/Fe3O4 nanoparticles using Euphorbia condylocarpa M. bieb root extract and their catalytic applications as magnetically recoverable and stable recyclable catalysts for the phosphine-free Sonogashira and Suzuki coupling reactions

This work reports on the green synthesis of Pd/Fe3O4 nanoparticles using Euphorbia condylocarpa M. bieb root extract as reducing agents and stabilizers and their catalytic applications in ligand- and copper-free Sonogashira and Suzuki coupling reactions. This method has such advantages as high yields, simple methodology and easy work up. In addition, the catalyst can be recovered by using a magnet and reused several times without significant loss of its catalytic activity. The catalyst was characterized using UV–vis, powder XRD, SEM and EDS techniques.

Green synthesis of water-dispersable palladium nanoparticles and their catalytic application in the ligand- and copper-free Sonogashira coupling reaction under aerobic conditions

Pd nanoparticles were prepared from PdCl2 by green method and were characterized with UV–vis, XRD and TEM methods. Catalytic studies indicated that Pd nanoparticles exhibited high activity for ligand-, amine- and copper-free Sonogashira coupling between aryl iodides and terminal alkynes under mild and aerobic conditions. This method has the advantages of high yields, simple methodology and easy work up. More importantly, the catalyst exhibits high catalytic activity, superior cycling stability and excellent substrate applicability.