Hollow nanoreactors for Pd-catalyzed Suzuki-Miyaura coupling and O-propargyl cleavage reactions in bio-relevant aqueous media.
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ABSTRACT:
SUBMITTER: Destito P
PROVIDER: S-EPMC6419927 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:This study describes the synthesis of novel amphiphilic linear-dendritic block copolymers and their self-assembly in water to form supramolecular nanoreactors capable of catalyzing Suzuki-Miyaura coupling reactions under "green" conditions. The block copolymers were formed through copper(I)-catalyzed alkyne-azide cycloaddition between azide functionalized poly(benzyl ether) dendrons as the perfectly branched blocks, as well as bis-alkyne modified poly(ethylene glycol), PEG, as the linear block. A first-generation poly(benzyl ether) dendron (G1) was coupled to a bis-alkyne modified PEG with molecular mass of 5 kDa, forming an ABA copolymer (G1)2-PEG5k-(G1)2 (yield 62%), while a second-generation dendron (G2) was coupled to a 11 kDa bis-alkyne modified PEG to produce (G2)2-PEG11k-(G2)2 (yield 49%). The structural purity and low dispersity of the linear-dendritic copolymers were verified by size-exclusion chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Their self-assembly was studied by dynamic light scattering, showing that (G1)2-PEG5k-(G1)2 and (G2)2-PEG11k-(G2)2 formed single populations of micelles (17 nm and 37 nm in diameter, respectively). The triazole rings located at the boundaries between the core and the corona are efficient chelating groups for transition metals. The ability of the micelles to complex Pd was confirmed by 1H NMR, transmission electron microscopy, and inductively coupled plasma. The catalytic activity of the supramolecular linear-dendritic/Pd complexes was tested in water by model Suzuki-Miyaura reactions in which quantitative yields were achieved within 3 h at 40 °C, while, at 17 °C, a yield of more than 70% was attained after 17 h.
| S-EPMC10096851 | biostudies-literature
Project description:Treatment of the imines a-c with palladium(II) acetate in acetic acid yielded the μ-acetate dinuclear complexes 1a-c, which readily reacted with sodium chloride or bromide to provide μ-halide analogues. The reaction of the latter with nitrogen, phosphorus and oxygen donor nucleophiles yielded new imine palladacycles following the cleavage of the Pd2X2 unit. The complexes were fully characterized by microanalysis, 1H, 13C and 31P NMR spectroscopies, as appropriate. The compounds were applied as catalysts in the Suzuki-Miyaura coupling reaction in aqueous and semi-aqueous media.
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Project description:The excesses of reagents used in protein chemistry are often incompatible with the reduced or even inverse stoichiometries used for efficient radiolabeling. Analysis and screening of aqueous Pd(0) ligand systems has revealed the importance of a guanidine core and the discovery of 1,1-dimethylguanidine as an enhanced ligand for aqueous Suzuki-Miyaura cross-coupling. This novel Pd catalyst system has now allowed the labeling of small molecules, peptides, and proteins with the fluorine-18 prosthetic [(18)F]4-fluorophenylboronic acid. These findings now enable site-specific protein (18)F-labeling under biologically compatible conditions using a metal-triggered reaction.
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Project description:Polymeric nanoparticles with reactive functional groups are an attractive platform for drug carriers that can be conjugated with drugs through a cleavable covalent linkage. Since the required functional groups vary depending on the drug molecule, there is a need for development of a novel post-modification method to introduce different functional groups to polymeric nanoparticles. We recently reported phenylboronic acid (PBA)-containing nanoparticles (BNP) with a unique framboidal morphology created via one-step aqueous dispersion polymerization. Since BNPs have high surface area due to their framboidal morphology and contain a high density of PBA groups, these particles can be used as nanocarriers for drugs that can bind to PBA groups such as curcumin and a catechol-bearing carbon monoxide donor. To further explore the potential of BNPs, in this article we report a novel strategy to introduce different functional groups to BNPs via the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction between the PBA groups and iodo- and bromo-coupling partners. We developed a new catalytic system that efficiently catalyzes Suzuki-Miyaura reactions in water without the need for an organic solvent, as confirmed by NMR. Using this catalyst system, we show that BNPs can be functionalized with carboxylic acids, aldehyde, and hydrazide groups while keeping their original framboidal morphology as confirmed via IR, alizarin red assay, and TEM. Furthermore, the potential of the functionalized BNP in drug delivery applications was demonstrated by conjugating the hydrogen sulfide (H2S)-releasing compound anethole dithiolone to carboxylic acid-functionalized BNPs and show their H2S-releasing capability in cell lysate.
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Project description:Herein, we report the crystal structure and characterization of mono-6-(l-aminopropanol)-deoxy-β-cyclodextrin (L n @β-CD). A highly efficient, in situ generated catalyst, PdCl2(L n @β-CD), was synthesized for palladium-catalyzed cross-coupling reactions under mild reaction conditions, and the use of this catalyst in Suzuki cross-couplings was investigated. Low palladium loadings of 0.01 mol % PdCl2(L n @β-CD) (Pd accounted for approximately 8.4% of the catalyst by mass) were found to be highly efficient for Suzuki cross-couplings in water and afforded the corresponding biaryl compounds in excellent yields. The catalyst can be recycled and reused.
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Project description:A novel strategy is described to prepare magnetic Pd nanocatalyst by conjugating lignin with Fe3O4 nanoparticles via activation of calcium lignosulfonate, followed by combination with Fe3O4 nanoparticles. Tethering 5-amino-1H-tetrazole to calcium lignosulfonate-magnetite hybrid through 3-chloropropyl triethoxysilane enabled coordination of Pd salt with Fe3O4-lignosulfonate@5-amino-1H-tetrazole. The underlying changes of the lignosulfonate are identified, and the structural morphology of attained Fe3O4-lignosulfonate@5-amino-1H-tetrazole-Pd(II) (FLA-Pd) is characterized by Fourier transform infrared, thermogravimetry differential thermal analysis, energy-dispersive spectrometry, field-emission scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometer (VSM). The synthesized FLA-Pd displayed high activity for phosphine-free C(sp2)-C(sp2) coupling in water, and the catalyst could be reused for seven successive cycles.
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Project description:The Suzuki-Miyaura reaction between the aryl halide (1) and the phenyl boronic acid (2), in the presence of the palladium(0) complex (3) as catalyst, gives the cross-coupling product (4) in quantitative yield when performed in basic aqueous solution of the nonionic surfactant Kolliphor-EL (K-EL). The partition between the aqueous and micellar environments of the species of this reaction has been investigated by means of Molecular Dynamics (MD) simulations. Starting from the K-EL molecules dispersed in water, a micelle model has been generated by MD simulations, adopting the 2016H66 force field. Reagent and product species have been described with the same force field, once the reliability of this force field has been tested comparing the n-octanol/water partition free energies calculated from the MD and Free Energy Perturbation (FEP) method with those obtained from the quantum-mechanical SMD method. The potential of mean force for the transfer process between water and the micellar phase of the different species has been calculated by the MD simulations and the Umbrella Sampling (US) method. The overall picture that emerges from these results confirms that the molecular species involved in this reaction prefers the micellar environment and concentrates in different but close zones of the micelle. This supports the experimental evidence that the use of suitable surfactant agents promotes reactivity, allowing micelles to behave as nanoreactors in which reactive species are solubilized and enhance their local concentration.
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Project description:Non-contact micro-manipulation tools have enabled invasion-free studies of fragile synthetic particles and biological cells. Rapid electrokinetic patterning (REP) traps target particles/cells, suspended in an electrolyte, on an electrode surface. This entrapment is electrokinetic in nature and thus depends strongly on the suspension medium's properties. REP has been well characterized for manipulating synthetic particles suspended in low concentration salt solutions (~ 2 mS/m). However, it is not studied as extensively for manipulating biological cells, which introduces an additional level of complexity due to their limited viability in hypotonic media. In this work, we discuss challenges posed by isotonic electrolytes and suggest solutions to enable REP manipulation in bio-relevant media. Various formulations of isotonic media (salt and sugar-based) are tested for their compatibility with REP. REP manipulation is observed in low concentration salt-based media such as 0.1× phosphate buffered saline (PBS) when the device electrodes are passivated with a dielectric layer. We also show manipulation of murine pancreatic cancer cells suspended in a sugar-based (8.5% w/v sucrose and 0.3% w/v dextrose) isotonic medium. The ability to trap mammalian cells and deposit them in custom patterns enables high-impact applications such as determining their biomechanical properties and 3D bioprinting for tissue scaffolding.
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Project description:Unlike their SCS analogues, SNS pincer complexes are poorly studied for their use in coupling reactions. Accordingly, a series of water soluble cationic Pd(II) SNS pincer complexes have been successfully synthesised and investigated in detail for their catalytic activity in Suzuki-Miyaura coupling reactions. By using only 0.5 mol % loading of the complexes, the coupling of inactivated aryl bromides and activated aryl chlorides with various boronic acids in water was achieved in excellent yields and the catalysts were found to be reusable for three cycles without a significant loss of activity. The investigation of the mechanism of the reaction revealed that a Pd(II) to Pd(IV) route is the more likely pathway which was further supported by computational studies.
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Project description:Palladium was immobilized on a highly porous copolymer of 4-vinylpyridine and divinylbenzene (polyHIPE-poly(high internal phase emulsion)) using palladium(II) acetate to obtain PolyPy-Pd with 6.1 wt % or 0.57 mmol Pd/g. The immobilized catalyst was able to catalyze the coupling of iodobenzene and phenylboronic acid in ethylene glycol monomethyl ether/water (3:1) within 4 h at rt and complete conversion was observed when 2.5 mol % of Pd per PhI was used. The reaction tolerated a wide range of substituents on the aromatic ring. Iodobenzene derivatives with electron-withdrawing substituents showed higher reactivity, while the opposite was true for the phenylboronic acid series. The polyHIPE-supported Pd catalyst was also used for the direct conversion of phenylboronic acid to biphenyl through an iodination/coupling reaction sequence. The recyclability of the heterogeneous catalyst was also optimized, and by finding a suitable combination of solvents for the loading of Pd, the reaction, and the isolation of the product, the solid-supported catalyst was completely regenerated and used in the next reaction with the same activity.
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