Sonogashira Cross-coupling Reaction Research Articles

Core-shell PdCu bimetallic colloidal nanoparticles in Sonogashira cross-coupling reaction: mechanistic insights into the catalyst mode of action.

Core-shell PdCu nanoparticles with different metal proportions were synthesized using a one-pot methodology and characterized by STEM, HRTEM, XANES and EXAFS analysis. The bimetallic nanoparticles were applied as catalysts in the Sonogashira cross-coupling reaction to investigate the mode of action of the PdCu in the reaction. The copper content directly influenced the generation of the cross-coupling product, shaping the performance of the catalyst. A quasi-homogeneous reaction pathway was evidenced by kinetics and poisoning experiments as well as XAS, HRTEM and HRMS analysis. These findings help to elucidate the mode of action of the PdCu nanocatalysts in the, as yet, unrevealed Sonogashira mechanism and the potential development of new nanocatalysts.

Mechanochemical synthesis of some heterocyclic molecules using Sonogashira cross-coupling reaction and their anticancer activities

A greener strategy for the synthesis of some functionalized heterocycles have been developed using Sonogashira cross-coupling reaction of furfural derived isoxazolidine and isoxazoline derivatives. This is a new approach for the functionalization of isoxazolidine and isoxazoline derivatives to modified heterocycles via cross-coupling reaction in solvent free ball-milling process. Since this kind of functionalization of cycloadducts to modified heterocycles via cross-coupling reaction are not known in literature, therefore, this approach will surely attract synthetic chemists to plan for this kind of reactions in organic synthesis. Significant anticancer activity of the new molecules added extra flavour in this synthesis. Simple reaction methodology, good to excellent yields and greener approaches are the important features noticed in this syntheses.

A new approach to large scale production of dimethyl sulfone: a promising and strong recyclable solvent for ligand-free Cu-catalyzed C–C cross-coupling reactions

Dimethyl sulfone (DMSN or MSM) was preparedviaefficient oxidation of dimethyl sulfoxide and used and developed as an efficient, viscose, and recyclable solvent for ligand-free CuI-catalyzed Heck, Suzuki, and Sonogashira cross-coupling reactions.

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.

Palladium-catalyzed highly regioselective mono and double Sonogashira cross-coupling reactions of 5-substituted-1,2,3-triiodobenzene under ambient conditions.

An efficient synthesis of 2,3-diiodinated diphenylacetylene and iodinated meta-terphenylacetylene derivatives through highly regioselective mono and double Sonogashira cross-coupling reactions of 5-substituted-1,2,3-triiodobenzene is reported. Significantly, the regioselectivity of coupling reactions is exclusively performed at the terminal C–I bonds, the less sterically hindered and the most regioactive positions. The highest isolated yields were achieved from reactions of electron-poor/neutral 1,2,3-triiodoarene and electron-rich arylacetylene derivatives. The use of 2.0 equiv. of arylacetylenes in one-pot fashion afforded the iodinated meta-terphenylacetylenes in excellent site selectivity and in good isolated yields. Different functional groups were found to be suitable under optimized conditions. This report discloses the first method to synthesize hitherto unknown 2,3-diiodinated diphenylacetylenes and iodinated meta-terphenylacetylenes that is facile, highly regioselective, general in scope and produces remarkable building blocks for other chemical transformations.

Electrophilic alkylation of arenes with 5-bromopyrimidine en route to 4-aryl-5-alkynylpyrimidines.

A new synthetic protocol for preparation of medicinally important 4-aryl-5-alkynylpyrimidines is described. The featured approach involves a sequence of chemo- and regioselective Brønsted acid-catalyzed electrophilic alkylation of arenes with 5-bromopyrimidine, followed by oxidative re-aromatization of the formed dihydropyrimidine ring. Finally, palladium-catalyzed Sonogashira cross-coupling reaction provided an end-game strategy.

Facile access to libraries of diversely substituted 2-aryl-benzoxazoles/benzothiazoles from readily accessible aldimines via cyclization/cross coupling in imidazolium-ILs with Pd(OAc)2 or NiCl2 (dppp) as catalyst

A two-step protocol involving Pd-catalyzed cyclization of readily accessible p-bromophenyl-aldimines to 2-bromophenyl-benzoxazole/benzothiazole in [BMIM][PF6] or [BMIM][BF4] as solvent, followed by the Suzuki, Heck, and Sonogashira cross-coupling reactions catalyzed by Pd or Ni is described that generates libraries of diversely substituted 2-aryl-/heteroaryl-benzoxazoles/benzothiazoles in respectable isolated yields under mild reaction conditions. The feasibility to perform the two-steps in sequence in one-pot starting from the aldimines is also demonstrated and the potential for recycling/reuse of the IL solvent is also shown.

Polyvinylpyrrolidone - Reduced Graphene Oxide - Pd Nanoparticles as an Efficient Nanocomposite for Catalysis Applications in Cross-Coupling Reactions

This paper reported a scientific approach adopting microwave-assisted synthesis as a synthetic route for preparing highly active palladium nanoparticles stabilized by polyvinylpyrrolidone (Pd/PVP) and supported on reduced Graphene oxide (rGO) as a highly active catalyst used for Suzuki, Heck, and Sonogashira cross coupling reactions with remarkable turnover number (6500) and turnover frequency of 78000 h-1. Pd/PVP nanoparticles supported on reduced Graphene oxide nanosheets (Pd-PVP/rGO) showed an outstanding performance through high catalytic activity towards cross coupling reactions. A simple, reproducible, and reliable method was used to prepare this efficient catalyst using microwave irradiation synthetic conditions. The synthesis approach requires simultaneous reduction of palladium and in the presence of Gaphene oxide (GO) nanosheets using ethylene glycol as a solvent and also as a strong reducing agent. The highly active and recyclable catalyst has so many advantages including the use of mild reaction conditions, short reaction times in an environmentally benign solvent system. Moreover, the prepared catalyst could be recycled for up to five times with nearly the same high catalytic activity. Furthermore, the high catalytic activity and recyclability of the prepared catalyst are due to the strong catalyst-support interaction. The defect sites in the reduced Graphene oxide (rGO) act as nucleation centers that enable anchoring of both Pd/PVP nanoparticles and hence, minimize the possibility of agglomeration which leads to a severe decrease in the catalytic activity.

Multisensing emissive 8-phenylethynylated 2′-deoxyadenosines and 2′-deoxyisoguanosines

Microenvironment-sensitive fluorescent nucleosides are highly important for biotechnological applications. Here, we report the synthesis and photophysical properties of various new 8-phenylethynylated 2′-deoxyadenosines and 2′-deoxyisoguanosines. 8-phenylethynylated 2′-deoxyadenosines are synthesized using Sonogashira cross-coupling reaction (76–91%), which are further transformed to 8-phenylethynylated 2′-deoxyisoguanosines (50–63%). All new compounds exhibit strong solvatochromicity and pH-dependent fluorescence in aqueous solutions. Furthermore, 8-phenylethynylated purine analogues are sensitive to solvent viscosity changes, indicating their potential sensitivity to environmental changes.

Visible-light-driven photo-Fenton degradation of organic pollutants by a novel porphyrin-based porous organic polymer at neutral pH.

Developing novel heterogeneous photo-Fenton catalysts with high efficiency and stability, driven by visible-light rather ultraviolet light at neutral pH has been a major challenge for degradation of organic pollutants. In this work, we successfully synthesized a metalloporphyrin-based porous organic polymer (FePPOP-1) by the Sonogashira cross-coupling reaction. UV-vis absorption spectra showed FePPOP-1 exhibits a significant coverage of the natural solar irradiance spectrum. As a result, the prepared FePPOP-1 has a significantly enhanced photocatalytic activity for the visible-light-driven degradation of methylene blue. By using only 4 mg of FePPOP-1 as a catalyst, it was found that 50 mL of organic wastewater containing 70 ppm MB could be totally degraded in 80 min even at neutral pH. The effects of the initial MB, H2O2 concentrations, pH value and common ions on MB degradation were studied in detail. Both the catalytic mechanism of FePPOP-1 and the degradation route of MB were also proposed.

Hydrothermally Synthesized CuCo2S4 Nanosheets as an Easily Accessible and Convenient Heterogeneous Catalyst for the Sonogashira Cross-Coupling Reactions

A high surface area and the possibility of high charge separation and transportability make the two-dimensional (2D) nanomaterials very special in many applications, particularly in the field of catalysis. The usefulness of 2D nanomaterial is positively demonstrated in this study by employing it as an efficient heterogeneous catalyst in Sonogashira cross-coupling reaction, where the later one is well known for the formation of carbon–carbon bonds. 2D nanosheets of CuCo2S4 are synthesized using a hydrothermal synthesis and the average thickness of the sheets is found to be in the range of 10−15 nm. The transparent nanosheets are interconnected to form thick sheets and then aggregated to form a highly open three-dimensional hierarchical structure. This study explores the Sonogashira reaction very efficiently in water/ethanol at room temperature using hydrothermally synthesized CuCo2S4 nanosheets as catalyst for the C-C coupling reaction for the first time. The developed method is found to be economic, green, high yields, low catalyst loading and reusability of the catalysts. This present CuCo2S4 nanosheet heterogeneous catalyst afford the Sonogashira coupling of various aryl halides with terminal alkynes, giving a variety of aryl acetylenes in excellent yields and can be recovered by a simple filtration and reused for at least ten consecutive reactions with almost constant yield and activity.

Sustainable dipolar homo-dicopper (II) dihydrazone complex as a catalyst for Sonogashira cross couplings

A novel dicopper (II) complex, Cu2L, was prepared form the complexation of the new polydentate ligand (H4L), bis(sodium 3-formyl-4-hydroxybenzenesulfonate)succinylhydrazone, with copper acetate. The novel homobinuclear complex was quite characterized by various physico-chemical tools and employed as a homogeneous and efficient-green catalyst for Sonogashira cross-couplings of phenylacetylene with halobenzenes under sustainable conditions. Cu2L exhibited very good catalytic performance with excellent chemoselectivity. The catalytic efficiency of Cu2L was improved by using ionic liquids–aqueous media (1: 1, binary mixture). A mechanistic pathway was also proposed for Cu(II)-catalyzed Sonogashira cross-coupling reactions for the reported finding. DFT for H4L and Cu2L were studied. Electronic configurations, energy of HOMO and LUMO orbitals, energy gap between orbitals (ΔE), electronegativity, hardness and softness were also calculated and compared with the applicable catalytic findings of Cu2L, which are in good conformity.

Synthesis of some mono and dialkynyl derivatives containing thieno[3,2-b]thiophene ring via Sonogashira alkynylation reaction

The Sonogashira cross-coupling reactions were used to synthesize 5 new monoalkynyl derivatives (10a-e) and 2 dialkynyl derivatives (12a-b) containing thieno[3,2-b]thiophene from monoaryl thieno[3,2-b]thiophen in moderate yield. The procedure was optimized and triphenylphosphine (0.2 eq.), palladium diacetate (0.1 eq), copper (I) iodide (0.2 eq.), THF, iPr2NH were found to be the best in these cases. The structures of the (10a-e) and (12a-b) compounds were elucidated by 1H and 13C NMR and mass spectral analysis.

Push–Pull Porphyrins via β‐Pyrrole Functionalization: Evidence of Excited State Events Leading to High‐Potential Charge‐Separated States

A new set of free-base and zinc(II)-metallated, β-pyrrole-functionalized unsymmetrical push-pull porphyrins were designed and synthesized via β-mono- and dibrominated tetraphenylporphyrins using Sonogashira cross-coupling reactions. The ability of donors and acceptors on the push-pull porphyrins to produce high-potential charge separated states was investigated. The porphyrins were functionalized at the opposite β,β'-pyrrole positions of porphyrin ring bearing triphenylamine push groups and naphthalimide pull groups. Systematic studies involving optical absorption, steady-state and time-resolved emission revealed existence of intramolecular type interactions both in the ground and excited states. The push-pull nature of the molecular systems was supported by frontier orbitals generated on optimized structures, wherein delocalization of HOMO over the push group and LUMO over the pull group connecting the porphyrin π-system was witnessed. Electrochemical studies were performed to visualize the effect of push and pull groups on the overall redox potentials of the porphyrins. Spectroelectrochemical studies combined with frontier orbitals helped in characterizing the one-electron oxidized and reduced porphyrins. Finally, by performing transient absorption studies in polar benzonitrile, the ability of push-pull porphyrins to produce charge-separated states upon photoexcitation was confirmed and the measured rates were in the range of 109 s-1 . The lifetime of the final charge separated state was around 5 ns. This study ascertains the importance of push-pull porphyrins in solar energy conversion and diverse optoelectronic applications, for which high-potential charge-separated states are warranted.

Synthesis of non-symmetrical alkynylpyridines by chemoselective Sonogashira cross-coupling reactions

4-Bromo-2,3,5-trichloro-6-iodopyridine was studied as a new substrate in chemoselective Sonogashira reactions. This approach provides an efficient access to non-symmetrical mono-, di-, tri- and pentaalkynylated pyridines in good yields. Selected pentaalkynylated pyridines were studied with regard to their UV/Vis- and emission properties showing moderate to high fluorescence quantum yields.

Designer 3D CoAl-layered double hydroxide@N, S doped graphene hollow architecture decorated with Pd nanoparticles for Sonogashira couplings

Hierarchical hollow flower-like CoAl–LDH assembled by N and S dual-doped graphene (N,S-G) was fabricated without any template for uniformly distribution of Pd nanoparticles. The resultant CoAl–LDH/N,S-G/Pd exhibited excellent activity in Sonogashira cross-coupling reactions. This hollow structure with large surface area exposes more accessible sites for anchoring metal species. Additionally, the synergistic doping of N and S can not only provide more defect sites by tuning the electronic properties, but also increase the electron density of Pd and enhance the unique interactions between metal particles and support. Moreover, the existence of reductive Co (II) sites within the support can capture and re-produce leached Pd particles, giving the composite long-term stability.

A New Heterogeneous Catalyst Obtained via Supramolecular Decoration of Graphene with a Pd2+ Azamacrocyclic Complex.

A new G-(H2L)-Pd heterogeneous catalyst has been prepared via a self-assembly process consisting in the spontaneous adsorption, in water at room temperature, of a macrocyclic H2L ligand on graphene (G) (G + H2L = G-(H2L)), followed by decoration of the macrocycle with Pd2+ ions (G-(H2L) + Pd2+ = G-(H2L)-Pd) under the same mild conditions. This supramolecular approach is a sustainable (green) procedure that preserves the special characteristics of graphene and furnishes an efficient catalyst for the Cu-free Sonogashira cross coupling reaction between iodobenzene and phenylacetylene. Indeed, G-(H2L)-Pd shows an excellent conversion (90%) of reactants into diphenylacetylene under mild conditions (50 °C, water, aerobic atmosphere, 14 h). The catalyst proved to be reusable for at least four cycles, although decreasing yields down to 50% were observed.

Facile Microwave-Assisted Synthetic Approach to Palladium Nanoparticles Supported on Copper Oxide as an Efficient Catalyst for Heck and Sonogashira Cross-Coupling Reactions

A simple green one-step method for the synthesis of highly active palladium nanoparticles embedded on copper oxide as an efficient catalyst for ligand-free Heck and Sonogashira cross-coupling reactions has been developed. The synthetic approach is based on Microwave (MW)-assisted simultaneous chemical reduction of an aqueous solution of palladium and copper salts using hydrazine hydrate as the reducing agent. Selected characterization of the catalyst with transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction spectroscopy (XRD) reveal a size range of 25[Formula: see text][Formula: see text][Formula: see text]2[Formula: see text]nm for the generated catalyst nanoparticles with the highest catalytic activity. The use of the generated Pd/CuO nanoparticles is highly advantageous due to the use of ethanol/water as an environmentally green solvent under mild reaction conditions. Furthermore, the synthesized Pd/CuO nanoparticles catalyst can be recycled and re-used up to five times with negligible effect on the efficiency having turnover number up to 6000 and turnover frequency reaching 72[Formula: see text]000[Formula: see text]h[Formula: see text] for 20[Formula: see text]wt.% Pd loaded catalyst at 150∘C.

Magnetic Cu–Schiff base complex with an ionic tail as a recyclable bifunctional catalyst for base/Pd-free Sonogashira coupling reaction

A Cu(II)–Schiff base complex containing imidazolium ionic phase was prepared and decorated on γ-Fe2O3 magnetic nanoparticles (γ-Fe2O3@Cu(II)IL-SB) and found to be an efficient catalyst for the Pd- and base-free Sonogashira coupling reaction. The heterogeneous catalyst was characterized by FTIR spectroscopy, UV–visible spectroscopy, FE-SEM, TEM, XRD spectroscopy, EDX spectroscopy, VSM, ICP spectroscopy, and atomic absorption spectroscopy. The coupling reactions were performed using the catalyst under mild and base-free conditions, and high-to-excellent yields were obtained for a variety of substrates. The catalyst demonstrates a dual-functionality arising from metal sites and imidazolium moieties and that the later plays a base role. Reusability and stability of γ-Fe2O3@Cu(II)IL-SB were studied several times, which can be reused up to eight consecutive runs with at least reduction in catalytic activity. Also, the mechanism of this bifunctional catalytic system was thoroughly investigated. A new and efficient method has been developed for the base- and Pd-free Sonogashira cross-coupling reactions of aryl halides with phenyl acetylene using a bifunctional γ-Fe2O3@Cu(II)IL-SB catalyst with imidazolium moiety under mild conditions

New (NHC)Pd(II)(PPh3) complexes: synthesis, characterization, crystal structure and its application on Sonogashira and Mizoroki–Heck cross-coupling reactions

In this study, new six Pd-based complexes containing mixture N-heterocyclic carbene (NHC) and triphenylphosphine (PPh3) ligands were synthesized from the reaction of the (NHC)PdI2(pyridine) with PPh3. The new (NHC)PdI2(PPh3) complexes were characterized using FTIR, 1H-NMR, 13C-NMR, and 31P-NMR spectroscopy and elemental analyses techniques. These spectra are consistent with the proposed formula. Molecular and crystal structure of two complexes was obtained using single-crystal X-ray diffraction method. Based on the crystal results, a cis geometry was assigned to all the complexes. These new complexes have been examined as the catalyst in the Sonogashira cross-coupling reaction. The catalytic conversions of the complexes were obtained between 71 and 99% from the reaction of phenylacetylene and aryl bromides. Also, these new complexes have been examined as the catalyst in the Mizoroki–Heck cross-coupling reaction. The catalytic conversions of the complexes were obtained between 80 and 100% from the reaction of styrene and aryl bromides.