Ester Coupling Reactions Research Articles

Self-cleaning catalytic membrane for water treatment via an integration of Heterogeneous Fenton and membrane process

Novel self-cleaning catalytic membranes are prepared for water treatment via an integration of heterogeneous Fenton and membrane process. Polysulfone (PSF) based functional copolymers with pendant ferrocene groups are facilely synthesized via a combination of controlled radical polymerization and ester coupling reaction. Different catalytic membranes with tuned surface hydrophilicity are then prepared through non-solvent phase inversion method based on functional ferrocene- and hydroxyl-containing PSF. These membranes have demonstrated high activity in catalyzing Fenton-type reactions, which also lead to outstanding antifouling performance for the membrane. Finally, the catalytic membranes are successfully used for treatment of waste water containing different dyes. The proposed strategy in this work may provide worthy guidance to catalytic membranes, which is promising for water purification through simultaneous Fenton reaction and membrane separation.

Toughening of epoxy thermosets with nano‐sized or micron‐sized domains of poly(ethylene oxide)‐b‐poly(butadiene‐co‐acrylonitrile)‐b‐poly(ethylene oxide) triblock copolymers synthesized using room temperature ester coupling reaction

AbstractPoly(ethylene oxide)‐b‐poly(butadiene‐co‐acrylonitrile)‐b‐poly(ethylene oxide) (PEO‐b‐PBN‐b–PEO) triblock copolymers with three different compositions were synthesized from poly(ethylene glycol) methyl ethers and carboxylic acid‐terminated poly(butadiene‐co‐acrylonitrile) (CTBN) by ester coupling reaction at room temperature. The PEO‐b‐PBN‐b‐PEO was incorporated into anhydride cured epoxy thermosets to improve the fracture toughness by the formation of either nano‐sized spherical micelles or micron‐sized vesicles. The polymer chemical structure was confirmed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, and gel permeation chromatography. The morphology of PEO‐b‐PBN‐b–PEO within the epoxy thermosets was investigated using a transmission electron microscope, an atomic force microscope, and a scanning electron microscope. Also, we conducted impact testing and plane‐strain fracture toughness testing to evaluate the fracture toughness in terms of the impact strength and the critical stress intensity factors (KIC) for the modified epoxy thermosets. The results revealed that all the PEO‐b‐PBN‐b‐PEO triblock copolymers are more effective in the toughening of epoxy thermoset compare to CTBN. We found that the 5 wt% PEO‐b‐PBN‐b‐PEO modified epoxy thermoset containing micron‐sized vesicles exhibited the highest KIC, which was 3.23 times as high as the KIC of pristine epoxy thermoset. Besides, the glass transition temperature remained and the tensile modulus did not reduce remarkably when the amount of PEO‐b‐PBN‐b‐PEO added into epoxy was 5 wt%.

Efficient Antibacterial and Low Cytotoxic Potential of Silver Nanoparticles Produced Instantaneously Using Dimeric Gallate

AbstractThis study reports the instantaneous synthesis of stable silver nanoparticles (AgNPs) at room temperature using a digallate (DG) derivative linked through hydrophilic oxyethylene spacer. The DG derivative was synthesized using standard ester coupling reaction and employed for the production of AgNPs. The Digallate acted as a very strong reducing and stabilizing agent as it reduced Ag ions in an aqueous media into Ag nanoparticles (DG‐AgNPs) instantaneously at room temperature. The DG‐AgNPs were characterized by UV/Vis, XPS, XRD, HR‐TEM, SEM, AFM, DLS and zeta potential measurements and were evaluated for their antibacterial potential against four different strains (Escherichia coli, Staphylococcus aureus, Streptomyces griseus and Bacillus subtilis). It demonstrated strong inhibitory activity with minimum inhibitory concentrations (MIC) ranging from 4.0‐6.0 μg/ml against all the tested bacterial strains. Optical density (OD) measurements and live/dead cell staining assay revealed significant antibacterial action of DG‐AgNPs. The MTT based cytotoxicity, cellular morphology and nuclear staining analysis of NIH 3T3 cells (fibroblasts) suggested DG‐AgNPs to be relatively safe as it did not reveal any growth inhibition for the optimized antibacterial concentrations. Concisely, relatively non‐toxic AgNPs have been produced rapidly at room temperature using dimeric gallate and suggested as effective and promising antibacterial agent for pharmaceutical applications.

ChemInform Abstract: Ester Coupling Reactions — An Enduring Challenge in the Chemical Synthesis of Bioactive Natural Products

AbstractReview: 285 refs.

Ester coupling reactions--an enduring challenge in the chemical synthesis of bioactive natural products.

In this review we investigate the use of complex ester fragment couplings within natural product total synthesis campaigns. We first outline the different biosynthetic and chemical strategies for performing complex ester couplings and on this mechanistic background we then present and discuss a collection of successful examples from the literature.

Assembled nanoparticle films with crown ether–metal ion “sandwiches” as sensing mechanisms for metal ions

Specialized nanoparticles known as monolayer-protected clusters (MPCs) were affixed with metal selective crown ether (CE) functional groups and assembled into novel thin films to form potential metal ion sensing materials. Films of MPCs modified with potassium specific 15-crown-5 ligands (CE-MPCs) were successfully assembled using both dithiol linkages and ester-coupling reactions. Film responses to potassium are observed spectroscopically as the manifestation of changing interparticle spacing within a film in the presence and absence of potassium. Growth dynamics, film structure, and metal response are examined. Additionally, the important role of flexibility, especially in the interconnectivity of the CE-MPCs within the film and between the CE groups themselves, is experimentally identified.

Dendritic functionalization of monolayer-protected gold nanoparticles

This paper describes the facile synthesis of nanoparticle-cored dendrimers (NCDs) and nanoparticle megamers from monolayer-protected gold clusters using either single or multi-step reactions. First, 11-mercaptoundecanoic acid/hexanethiolate-protected gold clusters were synthesized using the Schiffrin reaction followed by the ligand place-exchange reaction. A convergent approach for the synthesis of nanoparticle-cored dendrimers uses a single step reaction that is an ester coupling reaction of hydroxy-functionalized dendrons with carboxylic acid-functionalized gold clusters. A divergent approach, which is based on multi-step reactions, employs the repetition of an amide coupling reaction and a Michael addition reaction to build polyamidoamine dendritic architectures around a nanoparticle core. Nanoparticle megamers, which are large dendrimer-induced nanoparticle aggregates with an average diameter of more than 300 nm, were prepared by the amide coupling reaction between polyamiodoamine [G-2] dendrimers and carboxylic acid-functionalized gold clusters. 1H NMR spectroscopy, FT-IR spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used for the characterization of these hybrid nanoparticles.

Covalently Networked Monolayer-Protected Nanoparticle Films

Covalently networked films of nanoparticles can be assembled on various substrates from functionalized monolayer-protected clusters (MPCs) via ester coupling reactions. Exposure of a specifically modified substrate to alternating solutions of 11-mercaptoundecanoic acid exchanged and 11-mercaptoundecanol exchanged MPCs, in the presence of ester coupling reagents, 1,3-dicyclohexylcarbodiimide and 4-(dimethylamino)pyridine, results in the formation of a multilayer film with ester bridges between individual nanoparticles. These films can be grown in a controlled manner to various thicknesses and exhibit certain properties that are consistent with films having other types of interparticle connectivity, including chemical vapor response behavior and quantized double layer charging. Ester coupling of MPCs into assembled films is a straightforward and highly versatile approach that results in robust films that can endure harsher chemical environments than other types of films. The stability of these covalent films is assessed and compared to other more traditional MPC film assemblies.

Samarium Diiodide Promoted Intramolecular Ketone—Ester Coupling Reaction: Novel Cyclization and Ring Expansion Pathway.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Samarium diiodide-promoted intramolecular ketone–ester coupling reaction: novel cyclization and ring expansion pathway

When ethyl 2-substituted-1-indanone-2-carboxylates were treated with samarium diiodide (SmI2), ring expansion products such as 3-substituted-1,2-naphthoquinones were isolated. Alcohols were also obtained as the mixture of cis- and trans-isomers of hydroxy and ester substituents. A reaction mechanism involving intramolecular addition of samarium ketyl radicals to ester substituents followed by ring expansion was proposed for the formation of the one-carbon homologated products. Similarly, reaction of ethyl 1-substituted-2-oxo-1-cyclopentanecarboxylates with SmI2 produced 3-substituted-2-hydroxy-2-cyclohexenones along with the corresponding alcohols.

Solid-phase synthesis of oligoesters using a JandaJel™ resin

This communication describes a general method for the solid-phase synthesis of oligomeric esters. A JandaJel™ resin was utilized as the solid support in conjunction with the highly acid labile Rink linker. Ester coupling reactions were performed using buffered reagents and the monomer was protected as its allyl ester. In this manner, ester coupling and deprotection could be performed under essentially neutral conditions, giving rise to products in both excellent yields and purity.

Interfacial Reactivity of Hydroxyl-Terminated Monolayers in the Absence of Solvents

We compare the interfacial reactivity between vapor- or liquid-phase heptanoyl chloride (C6COCl) and hydroxyl-terminated monolayers prepared from 4-hydroxythiophenol (HTP), 11-mercaptoundecanol (MUD), and a hydroxyl-terminated, fourth-generation poly(amidoamine) (PAMAM) dendrimer (G4-OH). Fourier transform infrared−external reflection spectroscopy indicates that both vapor- and liquid-phase C6COCl reacts with all three hydroxyl-terminated self-assembled monolayers (SAMs) to yield ester-coupled bilayers. The spectroscopic data were confirmed by contact-angle goniometry, which revealed advancing contact-angle increases of between 60 and 75° after vapor-phase reaction, and ellipsometric measurements, which indicated that the films increased in thickness by 0.4−0.6 nm. Similar results were obtained when the ester-coupling reaction was carried out in liquid-phase CH2Cl2. Real-time, quantitative surface acoustic wave (SAW)-based nanogravimetry indicates that the vapor-phase reactions go to completion in <1 min. The order of reactivity of the monolayers decreases in the order G4-OH > MUD > HTP. This is interpreted in terms of monolayer structure and the intrinsic properties of the particular coupling reaction studied.

Gateway Reactions to Diverse, Polyfunctional Monolayer-Protected Gold Clusters

Amide and ester coupling reactions of ω-functionalized monolayer-protected gold cluster molecules (MPCs) are an exceptionally efficient avenue to a diverse variety of polyfunctionalized MPCs starting from a small subset of ω-functionalized materials. In this paper, coupling reactions have been employed to produce 13 MPCs bearing multiple copies of a diverse variety of structural groups. Detailed features of three of the 13 polyfunctionalized products are highlighted: (a) stepwise coupling and deprotection reactions result in an MPC surrounded by ca. eight pendant tripeptides, (b) a preliminary Steady-State Electron Paramagnetic Resonance (SSEPR) experiment is described for MPCs bearing multiple spin labels (ca. 13/cluster), and (c) a polyelectron electrochemical reaction is described for an MPC bearing multiple (ca. 7/cluster) coupled phenothiazine derivatives. The coupling reactions substantially expand the available diversity of MPCs as polyfunctionalized chemical reagents platformed on a nanometer-sized central core.

Synthesis of [ 18F]fluoroetanidazole: A potential new tracer for imaging hypoxia

A method has been developed for the synthesis of [ 18F]fluoroetanidazole, a potential tracer for imaging hypoxia with positron emission tomography. The compound is prepared by an active ester coupling reaction between the 2,3,5,6-tetrafluorophenyl ester of 2-nitroimidazole acetic acid and [ 18F]fluoroethylamine. [ 18F]Fluoroethylamine is prepared from N-[2-(toluene-4-sulfonyloxy)-ethyl]-phthalimide and [ 18F]fluoride and purified by distillation. The overall reaction takes about 90 min and gives a yield, uncorrected, of about 25%. Purification on a reversed-phase column is straightforward.

Preparation of polystyrene labeled with amino groups at specific sites

AbstractThe preparation of monodisperse polystyrene substituted with single dimethylamino groups is described. Three methods are adopted. The first involves the use of a dimethylamino‐substituted initiator to give an end amino group. The second uses an ester coupling reaction with a dimethylamino‐substituted methyl valeric ester to give a central amino substituent. The third method, which is capable of giving an amino substituent at any selected place along the chain, uses a dimethyl‐amino‐substituted butadiene derivative as a comonomer in a sequential polymerization. This latter method takes advantage of the unusual reactivity ratios of styrene and dienes in anionic copolymerization.

ChemInform Abstract: PEPTIDE SYNTHESIS WITH 1‐AMINOCYCLOPROPANE‐1‐CARBOXYLIC ACID

AbstractVon der Titelverbindung (Ia) werden Derivate (Ib), (Ic) bzw. (Ie) [über (Id)] dargestellt, die in verschje‐ denen Modell‐Aktivester‐Reaktionen zu den Peptiden (IIIa) bzw. (?lb) [Weiterüberführung von (IIIa)‐(IVa)‐(IVb)‐(IVc)], (VI) [Weiterüberführung über die angegebenen Stufen in das Enkephalin‐Analoge (XI)] bzw. (XIIa) [Weiterüberführung in (XIIb)] umgesetzt werden.

Rate constants for peptide p-nitrophenyl ester coupling reactions in dimethylformamide. A model for steric interactions in the peptide bond forming transition state.

Rate constants for peptide p-nitrophenyl ester coupling reactions in dimethylformamide. A model for steric interactions in the peptide bond forming transition state.