Catalyzed Suzuki Miyaura Cross-coupling Reaction Research Articles

Ppm-Pd-Fe nanoparticles on charcoal: Palladium catalyzed Suzuki-Miyaura cross-coupling reactions of aryl triflates with aryl neopentylglycolboronates

Aryl triflate is a type of facile and readily available compounds, which could be used as an alternative substrate for Suzuki cross coupling. In this manuscript, a novel ppm-Pd-Fe/C catalyst has been developed by reduction of palladium acetate and iron trichloride with aqueous hydrazine in situ and supported on activated charcoal. In combined with Sphos, and metal zinc as additives, this catalyst, with 300 ppm palladium loading, could be applied in the Suzuki cross coupling between aryl triflates with aryl neopentylglycolboronates.

Micelle-Derived Palladium Nanoparticles for Suzuki–Miyaura Coupling Reactions in Water at Room Temperature

Despite the wide utility of colloidal palladium (Pd) nanoparticle (NP)-catalyzed Suzuki–Miyaura cross-coupling reactions in laboratory and industrial synthesis, the easy construction of colloidal Pd NPs and the detailed role of surfactants remain the focus of attention. Here, we present a simple and sustainable strategy to construct a nanoreactor by connecting micelles with Pd NPs. The strategy enables us to employ a pH-induced morphological transition of sugar-based surfactant aggregates, such as worm-like, spherical, and tubular micelles, to investigate the solubilization of organic substrates. Pd NPs are mainly synthesized by the reduction of phenylboronic acid, further stabilized by the sugar-based surfactant micelles. A kinetic model is established, and the apparent activation energy of this reaction in aqueous micellar solutions is determined to be 46.7 kJ/mol. Notably, the recycled aqueous reaction mixture containing the micelles and Pd NPs can be reused.

Microwave Irradiated, Sodium Aluminate Supported and Zinc Catalyzed Suzuki-Miyaura Cross-Coupling Reaction on Fused Tricyclic Oxa-Aza-Quinolone: A Green Protocol

Alternative synthesis methods are need of the hour to provide easy protocol for synthesizing biologically active heterocyclic compounds. In this connection, this paper describes the development of a concise, convergent protocol for diversely substituted Suzuki–Miyaura cross-coupling reactions of heteroaryl bromides and boronic acids under microwave irradiation using Sodium aluminate (NaAlO2) as a solid support as well as base. According to my knowledge, this is the first report of the strategy that involves the use of zinc as a catalyst on fused tricyclic di-halo quinolones in a solvent-free condition using simple microwave irradiation. Earlier research from the same laboratory established a solid support assisted Suzuki–Miyaura cross-coupling reaction for forming C–C bonds under the influence of microwave irradiation. Therefore, sodium aluminate (NaAlO2) was attempted as a base and solid support instead of traditional mineral bases. Moreover, zinc was used as a catalyst replacing palladium. The new method is unique and effective due to its energy economy, procedural simplicity, and general applicability. Moreover, the use of Sodium aluminate (NaAlO2) is expected to extend this green-protocol and atom-friendly chemistry for the synthesis of varied heterocyclic compounds of interest.

Minimizing base stoichiometry in Pd(0)/g-C3N4O catalyzed Suzuki–Miyaura cross-coupling reaction

A Pd nanoparticle supporting graphitic carbon nitride oxide (g-C3N4O) sheet is developed as an efficient heterogeneous catalyst for Suzuki–Miyaura cross-coupling reaction requiring just under a substoichiometric amount of exogenous base.

Synthesis of novel coumarin containing conjugated fluorescent polymers by Suzuki cross-coupling reactions and their chemosensing studies for iron and mercury ions

Conjugated fluorescent polymers are very useful materials for chemical and biochemical sensors. Herein we report the synthesis of four novel conjugated coumarin-containing fluorescent co-polymers (P1–P4) by palladium catalyzed Suzuki-Miyaura cross-coupling reaction. 4-Methyl/phenyl coumarin ditriflates and diboronic acids such as benzene-1,4-diboronic acid and 9,9-dioctylfluorene-2,7-diboronic acid were used as coupling partners. All the polymers were well-characterized using NMR and gel permeation chromatography. TGA studies revealed that these polymers are stable over 300 °C. The photophysical properties of these novel polymers were studied by UV–Vis and fluorescence spectroscopy. Among these four polymers, polymer P3 having 4-methylcoumarin and dioctylfluorene as alternating monomers showed intense fluorescence with 0.73 quantum yield in the DMF medium. Polymer P3 was also found as selective fluorescence “turned-off” chemosensor for the detection of Hg(II) and Fe(II)/Fe(III) ions over the other metal ions dissolved in water.

Synthesis of new functionalized triarylmethanes via Suzuki cross-coupling and Heck-type vinylation reactions

A novel class of triarylmethanes (TRAMs) containing one or two biaryl moieties was synthesized efficiently through the Pd(PPh 3 ) 4 -catalyzed Suzuki–Miyaura cross-coupling reaction of brominated TRAMs with arylboronic acid derivatives. We also demonstrate that brominated TRAMs can be efficiently functionalized via a one-pot, two-step Pd-catalyzed Heck-type process. This protocol provides convenient access to diverse vinylated TRAMs that are generally not obtained by using the common synthetic methods for TRAMs.

Synthesis, characterization and photophysical properties of π-conjugated novel phenothiazine substituted acrylonitrile D–A derivatives: Orange to red emission

• Phenothiazine substituted acrylonitrile derivatives are synthesized. • Optical band gap values range from 2.296 to 2.407 eV. • Measured experimental quantum yields ( φ) are range from 0.065 to 0.121. • The 5% weight loss temperatures of derivatives are in the range 170–250 °C. By utilizing palladium catalyzed Suzuki–Miyaura cross coupling reaction, a series of novel organic dyes containing phenothiazine were designed, synthesized (abbreviated as PTA-5(a–d)) in good yield and confirmed by spectroscopic methods. These bipolar dyes comprise of PTA moiety as the electron donor unit (D) and acrylonitrile as the electron acceptors/anchoring unit (A). By introducing substituents at C(3) and C(7) positions, Intramolecular Charge Transfer character of PTA was improved. Their photophysical/solvatochromic properties were examined with the assistance of DFT computations and the synthesized molecules exhibit red fluorescence with decent quantum yields. The computed and experimental results are found to be in accordance. Differential scanning calorimetry and thermogravimetric analysis showed the thermal stabilities of the compounds. The highest occupied molecular orbitals, lowest unoccupied molecular orbitals and energy band gap were computed with the help of frontier molecular orbitals. The outcome exhibit that the novel (D–A) chromophores could play important role in organic optoelectronics.

Core-shell iron oxide@cathecol-polymer@palladium/copper nanocomposites as efficient and sustainable catalysts in cross-coupling reactions

Magnetic core-shell Fe2O3@polymer-Pd/Cu nanocomposites (NCs) were developed as efficient and sustainable nanocatalysts for cross-coupling reactions. The designed NCs consisted of three components: i) a magnetic core (Fe2O3 nanoparticle), which allowed the recovery and reuse of the NCs, enhancing thus their attractiveness as green catalysts; ii) a catechol-based polymer coating, chosen because of its strong chelating ability towards metal ions, and its potential to be obtained from biomass (lignin depolymerization); and iii) catalytically active metal nanoparticles (Pd and Cu NPs) immobilized via in situ formation onto the polymeric shell. As-prepared Pd-based NCs successfully catalyzed Suzuki-Miyaura cross-coupling reactions, achieving yields between 87% and 97% in only 20–40 min depending on the aryl halides and boronic acid derivatives. Similarly, Cu-based NCs exhibited a quite good catalytic efficiency (> 80%) in the synthesis of propargylamines via A3 coupling reaction of phenylacetylene with various aldehydes and amines. Importantly, these NCs presented a good reusability, without significant decrease in efficiency after several cycles. However, the major advantage of the designed NCs is the lower Pd or Cu content (1.5 wt% and 2.6 wt%, respectively) as compared to most of the reported similar catalysts (between 3 – 6 wt% for Pd and > 5 wt% for Cu), which is a key challenge in view of developing cost-effective and environment-friendly catalysts while maintaining a high efficiency.

A Bulky Chiral N-Heterocyclic Carbene Palladium Catalyst Enables Highly Enantioselective Suzuki-Miyaura Cross-Coupling Reactions for the Synthesis of Biaryl Atropisomers.

Axially chiral biaryl scaffolds are essential structural units in chemistry. The asymmetric Pd-catalyzed Suzuki-Miyaura cross-coupling reaction has been widely recognized as one of the most practical methods for constructing atropisomers of biaryls. However, longstanding challenges remain in this field. For example, substrate scope is often narrow and specialized, functional groups and heterocycles can lead to reduced reactivity and selectivity, bulky ortho-substituents are usually needed, and reported methods are generally inapplicable to tetra-ortho-substituted biaryls. We have developed an unprecedented highly enantioselective N-heterocyclic carbene (NHC)-Pd catalyzed Suzuki-Miyaura cross-coupling reaction for the synthesis of atropisomeric biaryls. These reactions enable efficient coupling of aryl halides (Br, Cl) or aryl triflates with various types of aryl boron compounds (B(OH)2, Bpin, Bneo, BF3K), tolerate a remarkably broad scope of functional groups and heterocycles (>41 examples), employ low loading of catalyst (0.2-2 mol %), and proceed under mild conditions. The protocol provided general and efficient access to various atropisomeric biaryls and heterobiaryls in excellent enantioselectivities (up to99% ee) with no need of using bulky ortho-substituted substrates and was effective for the synthesis of tetra-ortho-substituent biaryls. Moreover, the method was successfully applied to the diastereo- and enantioselective synthesis of atropisomeric ternaphthalenes. Critical to the success of the reaction is the development and application of an extremely bulky C2-symmetric chiral NHC, (R,R,R,R)-DTB-SIPE, as the ligand for palladium. To the best of our knowledge, this is the first highly enantioselective (>90% ee) example of a chiral NHC-metal-catalyzed C(sp2)-C(sp2) cross-coupling reaction.

Preparation and characterization of PEPPSI-palladium N-heterocyclic carbene complexes using benzimidazolium salts catalyzed Suzuki–Miyaura cross coupling reaction and their antitumor and antimicrobial activities

New palladium complexes were efficiently synthesized from the reaction of benzimidazolium salts 2a–e, potassium carbonate (K2CO3) and palladium chloride (PdCl2) in pyridine (for 3a–e). The catalytic activity of these complexes in a catalytic system including palladium complexes and K2CO3 in DMF-H2O was evaluated in Suzuki–Miyaura cross-coupling reactions of aryl bromides and chlorides with phenylboronic acid. Our novel complexes show excellent catalytic activities with high turnover numbers (TON) and high turnover frequencies (TOF) (e.g. for the Suzuki–Miyaura reaction: TON up to 370 and TOF up to 123.3 h−1). Both benzimidazolium salts 2a–e and complexes 3 have been characterized using spectroscopic data and elemental analysis. The antimicrobial activity of the N-heterocyclic carbene palladium complexes 3a–e varies with the nature of the ligands. Also, the IC50 values of both, complexes (3a–e) and benzimidazoles 2a–e, have been determined. In addition, the new palladium complexes were screened for their antitumor activity. Complexes 3e and 3d exhibited the highest antitumor effect with IC50 values 6.85 μg/mL against MCF-7 and 10.75 μg/mL against T47D, respectively.

Heterogeneous Suzuki-Miyaura coupling of heteroaryl ester via chemoselective C(acyl)-O bond activation.

A site-selective supported palladium nanoparticle catalyzed Suzuki–Miyaura cross-coupling reaction with heteroaryl esters and arylboronic acids as coupling partners was developed. This methodology provides a heterogeneous catalytic route for aryl ketone formation via C(acyl)–O bond activation of esters by successful suppression of the undesired decarbonylation phenomenon. The catalyst can be reused and shows high activity after eight cycles. The XPS analysis of the catalyst before and after the reaction suggested that the reaction might be performed via a Pd0/PdII catalytic cycle that began with Pd0.

Synthesis, characterization and photophysical properties of a new class of pyrene substituted 1,3,4-oxadiazole derivatives

We have designed and synthesized a series of a new class of pyrene substituted 1,3,4- oxadiazole derivatives (abbreviated as 3(a-e)) through palladium catalyzed Suzuki-Miyaura cross coupling reaction. The chemical structures of the probes were characterized by using analytical techniques namely 1H NMR, 13C NMR, FT-IR and GC-MS. The novel bipolar molecules consist of pyrene as an electron donor unit (D) and electron-deficient 1,3,4-oxadiazole as an acceptor unit (A) linked via extending π conjugation through a phenyl spacer with para linkages (D-π-A). Intramolecular charge transfer is improved by structure-property relationship. The detailed photophysical/solvatochromic properties of newly synthesized derivatives have been studied employing steady state spectroscopic techniques. The photophysical studies revealed that compounds emit strong indigo-blue fluorescence and efficient blue emission extending into blue-green in solid phase with high quantum yields. Thermal and morphological stabilities of the derivatives were studied employing DSC and TGA measurements. In addition, density functional theory (DFT) computations have been carried out to demonstrate various intramolecular interactions that cause the stabilization of the compound leading to its optoelectronic applications. The highest occupied molecular orbital energy (HOMOs), lowest unoccupied molecular orbital energy (LUMOs), the energy bandgap, chemical hardness (η), softness (δ), electronegativity (χ) and chemical potential (μ) were computed with the help of frontier molecular orbitals. The results were compared and discussed with the experimental results. The results demonstrate that the novel pyrene containing oxadiazole derivatives could be used as small organic molecules for multifunctional organic light-emitting devices (OLED)/optoelectronic devices.

Lipidic Mesophase-Embedded Palladium Nanoparticles: Synthesis and Tunable Catalysts in Suzuki–Miyaura Cross-Coupling Reactions

Lipidic cubic phases (LCPs) can reduce Pd2+ salts to palladium nanoparticles (PdNPs) of ∼5 nm size in their confined water channels under mild conditions. The resulting PdNP-containing LCPs were used as nanoreactor scaffolds to catalyze Suzuki-Miyaura cross-coupling reactions in the aqueous channels of the mesophase. To turn on catalysis, PdNP-containing LCPs were activated by swelling the aqueous channels of the lipidic framework, thereby enabling diffusion of the water-soluble substrates to the catalysts. The mesophases play a threefold role: they act as reducing agents for Pd2+, as limiting templates for their growth, and as support. The system was characterized and investigated by small-angle X-ray scattering (SAXS), cryo-transmission electron microscopy, dynamic light scattering, and nuclear magnetic resonance. Bulk LCPs and three dispersed palladium/lipid hybrid nanoparticle types were applied in the catalysis. The latter-liposomes, hexosomes, and cubosomes-can be obtained by design through combination of lipids and additives. The Suzuki-Miyaura cross-coupling of 5-iodo-2'-deoxyuridine and phenylboronic acid was used as a model reaction to study these systems. Bulk Pd-LCPs deliver the Suzuki-Miyaura product in 24 h in conversions up to 98% at room temperature, whereas with palladium/lipid dispersions at 40 °C, 68% of the starting material was transformed to the product after 72 h.

Synthesis of Pyridazine Derivatives by Suzuki-Miyaura Cross-Coupling Reaction and Evaluation of Their Optical and Electronic Properties through Experimental and Theoretical Studies.

A series of π-conjugated molecules, based on pyridazine and thiophene heterocycles 3a–e, were synthesized using commercially, or readily available, coupling components, through a palladium catalyzed Suzuki-Miyaura cross-coupling reaction. The electron-deficient pyridazine heterocycle was functionalized by a thiophene electron-rich heterocycle at position six, and different (hetero)aromatic moieties (phenyl, thienyl, furanyl) were functionalized with electron acceptor groups at position three. Density Functional Theory (DFT) calculations were carried out to obtain information on the conformation, electronic structure, electron distribution, dipolar moment, and molecular nonlinear response of the synthesized push-pull pyridazine derivatives. Hyper-Rayleigh scattering in 1,4-dioxane solutions, using a fundamental wavelength of 1064 nm, was used to evaluate their second-order nonlinear optical properties. The thienylpyridazine functionalized with the cyano-phenyl moiety exhibited the largest first hyperpolarizability (β = 175 × 10−30 esu, using the T convention) indicating its potential as a second harmonic generation (SHG) chromophore.

Palladium immobilized on the surface of MMT K 10 with the aid of [BMIM][BF4]: An efficient catalyst for Suzuki-Miyaura cross-coupling reactions

The designing of a new heterogeneous catalyst for palladium catalyzed Suzuki-Miyaura cross-coupling reactions at room temperature is of great interest from green chemistry perspectives. In this work, neutral ionic liquid [BMIM][BF4] was used as an anchor for immobilizing palladium on the surface of MMT K 10. The procedure for the synthesis of the catalyst is quite simple and the entire process is conducted under room temperature. The catalyst formed consists of palladium nanoparticles which were characterized by TEM, SEM and XRD. The new heterogeneous catalyst showed excellent catalytic activity toward biaryl synthesis in water at room temperature.

Synthesis, crystal structure analysis, spectral IR, UV–Vis, NMR assessments, electronic and nonlinear optical properties of potent quinoline based derivatives: Interplay of experimental and DFT study

Quinoline and its derivatives are widely studied by both synthetic and computational chemists due to their exciting perspectives in biological and nonlinear optical (NLO) research. Herein, three novel arylated quinolines: 3-(4-acetylphenyl)quinoline (1), 3-(4-(methylthio)phenyl)-quinoline (2) and 3-(4-phenoxyphenyl)quinoline (3) were synthesized employing Pd catalyzed Suzuki–Miyaura cross-coupling reaction. The chemical structures of all compounds were resolved employing different analytical techniques like 1H-NMR, FT-IR, UV–Vis, EIMS, elemental analysis and finally confirmed by single crystal X-ray diffraction analysis. Synthesized compounds were further subjected to density functional theory (DFT) calculations at B3LYP level of theory in conjunction with 6-311 + G(2d,p) basis set to explore optimized geometry, natural bond orbital (NBO) analysis, FT-IR spectroscopic data, frontier molecular orbitals (FMOs) and NLO properties. Overall, a good agreement was found between DFT computed results and corresponding experimental findings. Vertical electronic transition states were computationally calculated using time-dependent DFT (TDDFT) at same B3LYP level of theory and 6-311 + G(2d,p) basis set combination. NBO calculations indicated the occurrence of intra-molecular charge transfer in synthesized compounds, hence enormous molecular stability owing to hyperconjugative interactions. Energy of FMOs was used to calculate the global reactivity descriptors which indicated that synthesized molecules are chemically hard compounds with greater kinetic stability and electron donating capability. NLO properties were found to be in the range 1830–2960 a.u and order of 2 > 1 > 3. Urea molecule comparative analysis and two-state model confirmed that synthesized molecules are excellent NLO candidates and may have prospective uses in the technology related applications.

Synthesis, Characterization, and Catalytic Studies of Dinuclear d8 Metal-Phosphazane Complexes.

Herein we report the synthesis and characterization of two diphosphazane (P-N-P) ligands, along with their corresponding novel palladium and platinum complexes. Compounds were characterized by FTIR and NMR spectroscopy, single crystal X-ray diffraction (SC-XRD), and powder X-ray diffraction (PXRD)), as well as mass spectrometry. The Pd(II) complex of the p-phenyldiphosphazane was shown to effectively and efficiently catalyze Suzuki-Miyaura cross-coupling reactions between a variety of substrates. Yields were as high as 96%, with reaction times as short as 15 min at room temperature and open to air. No additional supporting ligands, such as triphenylphosphine, were needed. The work reported here expands the use of phosphazane ligands to support catalytic centers and provides an understanding of phosphazane metal-ligand bonding interactions (specifically diphosphazanes).

Ligand-Controlled Chemoselective C(acyl)-O Bond vs C(aryl)-C Bond Activation of Aromatic Esters in Nickel Catalyzed C(sp2)-C(sp3) Cross-Couplings.

A ligand-controlled and site-selective nickel catalyzed Suzuki-Miyaura cross-coupling reaction with aromatic esters and alkyl organoboron reagents as coupling partners was developed. This methodology provides a facile route for C(sp2)-C(sp3) bond formation in a straightforward fashion by successful suppression of the undesired β-hydride elimination process. By simply switching the phosphorus ligand, the ester substrates are converted into the alkylated arenes and ketone products, respectively. The utility of this newly developed protocol was demonstrated by its wide substrate scope, broad functional group tolerance and application in the synthesis of key intermediates for the synthesis of bioactive compounds. DFT studies on the oxidative addition step helped rationalizing this intriguing reaction chemoselectivity: whereas nickel complexes with bidentate ligands favor the C(aryl)-C bond cleavage in the oxidative addition step leading to the alkylated product via a decarbonylative process, nickel complexes with monodentate phosphorus ligands favor activation of the C(acyl)-O bond, which later generates the ketone product.

Synthesis, characterization and aggregation-induced emission of alternating copolymers containing cyclophanes and tetraphenylethenes

The alternating copolymers containing tetraphenylethenes bonded to pseudo-para or pseudo-meta [2.2]paracyclophanes were synthesized by palladium catalyzed Suzuki-Miyaura cross-coupling reaction. Relatively high molecular weights of polymers were obtained by the reaction of their corresponding comonomers using Pd(OAc)2 as a catalyst with S-Phos as a ligand and K3PO4 as a base under a high base to monomer ratio. The maximum emission intensity of polymer in THF increases gradually as the addition of water fraction increases. The polymers exhibited aggregation-induced emission in aggregated state. In particular, the photoluminescence quantum yield of those tetraphenylethenes bonded to pseudo-meta [2.2]paracyclophanes is up to 0.334 when the water fraction reaches to 90%. The polymers used in the detection of 2,6-dinitrotoluene are more sensitive than that of small molecule containing the same conjugated segment of the polymers. They are promising candidates for potential uses in the optoelectronic applications.

Conjugated polymer nanoparticles based on fluorenes, PEGylated carbazoles and diphenylamines

Novel conjugated polymers containing fluorenes, PEGylated carbazoles and diphenylamines were synthesized by the palladium catalyzed Suzuki-Miyaura cross-coupling reaction. The dimensions of the conjugated polymer nanoparticles were in a range of 35–65 nm as observed by SEM analysis. A blue-shifted absorption of the conjugated polymer nanoparticles containing fluorenes and diphenyl amines or 2,7-linked carbazoles was observed compared to that of the polymer solution, this can be attributed to aggregation-induced disorder. The emission of the polymer nanoparticles containing fluorenes and carbazoles is red-shifted and this can be attributed to the increase in interchain interactions possibly due to conjugated polymer chains collapsing in water during nanoparticle formation. For all polymers, the decreases in emission quantum yields on going from polymer solution to nanoparticle dispersion were reflected the aggregation of the polymer chains in aqueous media.