Showing papers on "Reagent published in 2017"
TL;DR: Fenton's reagent was used to isolate microplastics from organic-rich wastewater, enabling its use as a pre-treatment method for focal plane array-based micro-FT-IR imaging and offers a considerable reduction in sample preparation times.
221 citations
TL;DR: Investigations suggested that RNH3 Cl acted as the chlorinating source, controlled the size, and also helps in increasing the number of particles, which provided more opportunity for Mn ions to take part in reaction and occupied the appropriate lattice positions.
Abstract: Doping in perovskite nanocrystals adopts different mechanistic approach in comparison to widely established doping in chalcogenide quantum dots The fast formation of perovskites makes the dopant insertions more competitive and challenging Introducing alkylamine hydrochloride (RNH3 Cl) as a promoting reagent, precise controlled doping of MnII in CsPbCl3 perovskite nanocrystals is reported Simply, by changing the amount of RNH3 Cl, the Mn incorporation and subsequent tuning in the excitonic as well as Mn d-d emission intensities are tailored Investigations suggested that RNH3 Cl acted as the chlorinating source, controlled the size, and also helps in increasing the number of particles This provided more opportunity for Mn ions to take part in reaction and occupied the appropriate lattice positions Carrying out several reactions with varying reaction parameters, the doping conditions are optimized and the role of the promoting reagent for both doped and undoped systems are compared
177 citations
TL;DR: An ionic cobalt-PNP complex is developed for the efficient α-alkylation of ketones with primary alcohols for the first time and was successfully applied to the greener synthesis of quinoline derivatives while using 2-aminobenzyl alcohol as an alkylating reagent.
166 citations
TL;DR: The dehydrogenative cross-coupling of aniline derivatives to 2,2'-diaminobiaryls is reported, carried out electrochemically, which avoids the use of metals and reagents and provides quick and efficient access to important building blocks featuring free amine moieties.
Abstract: The dehydrogenative cross-coupling of aniline derivatives to 2,2′-diaminobiaryls is reported. The oxidation is carried out electrochemically, which avoids the use of metals and reagents. A large variety of biphenyldiamines were thus prepared. The best results were obtained when glassy carbon was used as the anode material. The electrosynthetic reaction is easily performed in an undivided cell at slightly elevated temperature. In addition, common amine protecting groups based on carboxylic acids were employed that can be selectively removed under mild conditions after the cross-coupling, which provides quick and efficient access to important building blocks featuring free amine moieties.
156 citations
TL;DR: An operationally simple, mild, redox-neutral method for the photoredox alkylation of imines is reported, which is highly selective, metal-free, and does not require a large excess of the alkylating reagent or the use of acidic additives.
Abstract: An operationally simple, mild, redox-neutral method for the photoredox alkylation of imines is reported. Utilizing an inexpensive organic photoredox catalyst, alkyl radicals are readily generated from the single-electron oxidation of ammonium alkyl bis(catecholato)silicates and are subsequently engaged in a C-C bond-forming reaction with imines. The process is highly selective, metal-free, and does not require a large excess of the alkylating reagent or the use of acidic additives.
128 citations
TL;DR: The first electrochemical dehydrogenative C-C cross-coupling of thiophenes with phenols has been realized and this sustainable and very simple to perform anodic coupling reaction enables access to two classes of compounds of significant interest.
Abstract: The first electrochemical dehydrogenative C-C cross-coupling of thiophenes with phenols has been realized. This sustainable and very simple to perform anodic coupling reaction enables access to two classes of compounds of significant interest. The scope for electrochemical C-H-activating cross-coupling reactions was expanded to sulfur heterocycles. Previously, only various benzoid aromatic systems could be converted, while the application of heterocycles was not successful in the electrochemical C-H-activating cross-coupling reaction. Here, reagent- and metal-free reaction conditions offer a sustainable electrochemical pathway that provides an attractive synthetic method to a broad variety of bi- and terarylic products based on thiophenes and phenols. This method is easy to conduct in an undivided cell, is scalable, and is inherently safe. The resulting products offer applications in electronic materials or as [OSO]2- pincer-type ligands.
121 citations
TL;DR: Efficacy of the sonolysis process was hampered in wastewater matrix, mainly as the consequence of higher pH increasing the molecule solubility, but after convenient acidification, sono-Fenton oxidation results remained almost unchanged, indicating no significant radical scavenging effects from the effluent compounds.
118 citations
TL;DR: A sulfonylative variant of a “classic” cross-coupling, with a broad substrate scope, and the electrophilic trapping of a sulfinate intermediate was possible.
Abstract: Using a simple copper(I) catalyst has allowed a high yielding sulfonylative-Suzuki–Miyaura cross-coupling reaction to be developed. The process provides a single step route to diaryl sulfones from the direct combination of aryl boronic acids, sulfur dioxide and aryl iodides, and represents the first sulfonylative variant of a classic cross-coupling reaction. Sulfur dioxide is delivered from the surrogate reagent, DABSO. Variation of the reaction conditions allowed interruption of the sulfonylative-Suzuki coupling, resulting in the formation of a presumed Cu–sulfinate intermediate. These sulfinates could be trapped as their sodium salts and treated with electrophiles to allow access to arylalkyl sulfones, β-hydroxyl sulfones, sulfonamides and sulfonyl fluorides.
106 citations
TL;DR: The first example of an asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with triflu oromethyl arylsulfonate (TFMS) as a new trif fluorinated organic compounds reagent is presented.
Abstract: The first example of an asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes has been described with trifluoromethyl aryl sulfonate as a new trifluoromethoxylation reagent. This reaction is operationally simple, scalable and proceeds under mild reaction conditions, which can be applied to the late-stage trifluoromethoxylation of complex small molecules.
99 citations
TL;DR: In this paper, a cost effective method of using thiol functionalized γ-aluminum oxide hydroxide (γ-AlOOH) filters for removing three key heavy metals from water: mercury, lead, and cadmium under non-concomitant conditions.
94 citations
TL;DR: Selective bromination of γ-methylene C(sp3 )-H bonds of aliphatic amides and δ- methylene C-H Bonds of nosyl-protected alkyl amines are developed using NBS as the brominating reagent and catalytic amount of CuII /phenanthroline complexes as the catalyst.
Abstract: Selective bromination of γ-methylene C(sp3 )-H bonds of aliphatic amides and δ-methylene C(sp3 )-H bonds of nosyl-protected alkyl amines are developed using NBS as the brominating reagent and catalytic amount of CuII /phenanthroline complexes as the catalyst. Aryl and benzylic C-H bonds at other locations remain intact during this directed radical abstraction reaction.
TL;DR: A novel and efficient Fe-catalyzed direct C-H amination (NH2 ) of arenes is reported using a new redox-active aminating reagent that has a broad substrate scope and could be used in the late-stage modification of bioactive compounds.
Abstract: A novel and efficient Fe-catalyzed direct C-H amination (NH2 ) of arenes is reported using a new redox-active aminating reagent. The reaction is simple, and can be performed under air, mild, and redox-neutral conditions. This protocol has a broad substrate scope and could be used in the late-stage modification of bioactive compounds. Mechanistic studies demonstrate that a radical pathway could be involved in this transformation.
TL;DR: A convenient, highly efficient, and selective transformation of aliphatic and aromatic carboxylic acids to acyl fluorides is reported, compatible with late-stage synthetic applications, high functional group tolerance, and facile target compound purification via filtration.
TL;DR: The influence of using hydrogen or nitrogen as carrier/reagent gas in catalytic cracking of soybean oil was studied in this paper, where the used catalyst was commercial zeolite ZSM-5 with Si/Al molar ratio of 20.07g/min with gas flow rate of 42mL/min at 723k for 45min.
TL;DR: The reduction of several enamines by SmI2(H2O)n shows that this reagent is a very strong hydrogen atom donor as well as an outer-sphere reductant.
Abstract: Samarium diiodide in the presence of water and THF (SmI2(H2O)n) has in recent years become a versatile and useful reagent, mainly for reducing carbonyl-type substrates. This work reports the reduction of several enamines by SmI2(H2O)n. Mechanistic experiments implicate a concerted proton-coupled electron transfer (PCET) pathway, based on various pieces of evidence against initial outer-sphere electron transfer, proton transfer, or substrate coordination. A thermochemical analysis indicates that the C–H bond formed in the rate-determining step has a bond dissociation free energy (BDFE) of ∼32 kcal mol–1. The O–H BDFE of the samarium aquo ion is estimated to be 26 kcal mol–1, which is among the weakest known X–H bonds of stable reagents. Thus, SmI2(H2O)n should be able to form very weak C–H bonds. The reduction of these highly electron rich substrates by SmI2(H2O)n shows that this reagent is a very strong hydrogen atom donor as well as an outer-sphere reductant.
TL;DR: This protocol describes the environmentally benign N-formylation and N-methylation of primary and secondary amines using carbon dioxide (CO2) as the carbon source, hydrosilanes as reductants andN-heterocyclic carbenes (NHCs) as catalysts.
Abstract: N-formylation and N-methylation of amines are important reactions that are used to produce a wide range of key intermediates and compounds. This protocol describes the environmentally benign N-formylation and N-methylation of primary and secondary amines using carbon dioxide (CO2) as the carbon source, hydrosilanes as reductants and N-heterocyclic carbenes (NHCs) as catalysts. Using CO2 as a reagent has the advantage of low cost and negligible toxicity. However, the catalyst is air-sensitive and must be generated fresh before use; consequently, the techniques used to prepare and manipulate the catalyst are described. The synthetic approach described in this protocol does not use any toxic reagents; using the appropriate catalyst, N-formylated or N-methylated products can be obtained with high selectivity. The overall time for catalyst preparation and for conducting several catalytic reactions in parallel is 15-48 h, depending on the nature of the substrates.
TL;DR: In this paper, a mesoporous phenol-formaldehyde resin-supported copper nanoparticles (NPs@MP) was used for the synthesis of ynones from acyl chlorides and terminal alkynes.
TL;DR: A copper-catalyzed substitution reaction of propargylic ammonium salts with aryl Grignard reagents is developed that is stereospecific and α-regioselective and proceeds with exceptional functional group tolerance.
Abstract: We have developed a copper-catalyzed substitution reaction of propargylic ammonium salts with aryl Grignard reagents. The reaction is stereospecific and α-regioselective and proceeds with exceptional functional group tolerance. Conveniently, a stable, inexpensive, and commercially available copper salt is used and no added ligand is required.
TL;DR: An electrophilic shelf-stable monofluoromethylthiolating reagent S-(fluorometHyl) benezenesulfonothioate (1) was developed and addition of reagent 1 to alkyl alkenes in the presence of a silver catalyst gaveAlkyl monofLUoromet hylthioethers in high yields.
Abstract: An electrophilic shelf-stable monofluoromethylthiolating reagent S-(fluoromethyl)benezene sulfonothioate 1 was developed. In the presence of a copper catalyst, reagent 1 coupled with a variety of aryl boronic acids to give the corresponding monofluoromethylthiolated arenes in high yields. In addition, addition of reagent 1 to alkyl alkenes in the presence of a silver catalyst gave alkyl monofluoromethylthioethers in high yields.
TL;DR: In this article, the authors found that hydrogen and oxygen recombination took place rapidly in the Pt/TiO 2 dispersion and resulted in very low hydrogen generation rate in pure water.
Abstract: Recently, photocatalytic hydrogen generation from water-semiconductor catalyst dispersion attracted world-wide attention because the solar energy could be converted directly into hydrogen only in very simple set-up in scale-up scale. Although many photocatalysts were reported to be active for this reaction, the efficiency is still quite low. In this work, we found that hydrogen and oxygen recombination took place rapidly in the Pt/TiO 2 dispersion and resulted in very low hydrogen generation rate in pure water. The activation energy of H 2 and O 2 recombination reaction is 16.5 kJ/mol regardless of light irradiation or not. In this case, the photocatalytic evolved H 2 could react rapidly with the evolved O 2 to form H 2 O again, eventually leading to no net H 2 and O 2 evolution during irradiation. The recombination of hydrogen and oxygen can be inhibited by addition of oxygen transfer reagent hemin chloride (HC). With help of HC, photocatalytic generated oxygen was captured by HC and transferred away from photocatalyst surface, then the backward reaction of hydrogen-oxygen recombination was successfully restrained. The photocatalytic hydrogen evolution amount in Pt/TiO 2 dispersion was significantly enhanced under this condition. The isotopes analysis results confirmed that both the H 2 and O 2 were from water. The HC could be recycled by releasing the O 2 with Ar gas bubbling. The HC could be poisoned by carbon monoxide and lost its oxygen transfer property, therefore no hydrogen could be formed under irradiation. This study clarified the main impediment reason of low efficient photocatalytic hydrogen generation in semiconductor-water dispersion and present available method to avoid this negative reaction. This finding will help to design high active catalytic system for solar energy to hydrogen conversion and open a new window for overall water splitting research.
TL;DR: In this paper, a novel reaction setup equipped with an elliptical cylindrical reflector to focus the radiation on the reactor has been used, being possible to control the reaction temperature.
TL;DR: Although this Communication focuses primarily on reactions with cyanide as nucleophile, preliminary experiments with other nucleophiles foreshadow the broad reaching synthetic utility of this approach.
Abstract: Herein is reported the design and application of a reagent for the direct functionalization of pyridines. These reactions occur under mild conditions and exhibit broad functional group tolerance, enabling the late-stage functionalization of drug-like molecules. The reagent can be easily prepared on large scale from inexpensive reagents, and reacts in the title reaction with acetonitrile, sodium chloride, and sodium methanesulfonate as the sole byproducts. Although this Communication focuses primarily on reactions with cyanide as nucleophile, preliminary experiments with other nucleophiles foreshadow the broad reaching synthetic utility of this approach.
TL;DR: This study provides important mechanistic insights for the cross-coupling reaction between alkyl halides and Grignard reagents and guides the design of efficient Fe-based catalysts for cross-Coupling reactions.
Abstract: The mechanism of the full catalytic cycle for Fe-chiral-bisphosphine-catalyzed cross-coupling reaction between alkyl halides and Grignard reagents (Nakamura and co-workers, J. Am. Chem. Soc. 2015, 137, 7128) was rationalized by using density functional theory (DFT) and multicomponent artificial force-induced reaction (MC-AFIR) methods. The computed mechanism consists of (a) C–Cl activation, (b) transmetalation, (c) C–Fe bond formation, and (d) C–C bond formation through reductive elimination. Our survey on the prereactant complexes suggested that formation of FeII(BenzP*)Ph2 and FeI(BenzP*)Ph complexes are thermodynamically feasible. FeI(BenzP*)Cl complex is the active intermediate for C–Cl activation. FeII(BenzP*)Ph2 complex can be formed if the concentration of Grignard reagent is high. However, it leads to biphenyl (byproduct) instead of the cross-coupling product. This explains why slow addition of Grignard reagent is critical for the cross-coupling reaction. The MC-AFIR method was used for systematic...
TL;DR: In this article, the authors examined the direct influence of ligand coverage on a catalytically active surface for the hydrogen evolution reaction (HER) and found that ligand stripping significantly reduced the coverage of amine and led to an improvement in the overpotential for HER.
Abstract: In this work, we examine the direct influence of ligand coverage on a catalytically active surface for the hydrogen evolution reaction (HER). We tested the electrochemical and electrocatalytic properties of colloidally synthesized WSe2 with dodecylamine ligands before and after treatment with Meerwein’s reagent, which was shown to reduce the coverage of amine and lead to an improvement in the overpotential for HER by as much as 180 mV on the same electrode (reversible upon re-ligation with amine). The underlying mechanism of the improvement in HER catalysis following treatment with Meerwein’s reagent was investigated using a combination of Tafel slope analysis, electrochemically active surface area measurements, and impedance spectroscopy. These electrochemical measurements are rationalized with Fermi level and d-band center analysis from XPS. Together, these measurements suggest that, while the surface area of the WSe2 increases upon ligand stripping, the intrinsic catalytic capability of the WSe2 also c...
TL;DR: In this paper, a Schiff base-modified silver catalyst was developed for the direct carboxylation of terminal alkynes with CO2, enabling an efficient and green synthesis of valuable alkynyl carboxylic acids.
TL;DR: This selective practical protocol can be successfully extended to direct methylation of highly functionalized bioactive compounds including 3-aminoestrone, cinacalcet, and their analogues in excellent yields and selectivities, highlighting their potential application in pharmaceuticals.
Abstract: Using feedstock methanol as a green methylation reagent, the selective N-monomethylation of anilines is realized under mild reaction conditions by using N-heterocyclic carbene iridium (NHC-Ir) coordination assemblies as highly efficient solid molecular catalysts. Along with a broad substrate scope and good functional group tolerance, up to quantitative yield and 2.0 × 104 turnover numbers (TONs) are obtained even at low catalyst loadings. Notably, the solid NHC-Ir molecular catalyst can be easily recovered and recycled more than 20 times without obvious loss of reactivity and selectivity. Furthermore, this selective practical protocol can be successfully extended to direct methylation of highly functionalized bioactive compounds including 3-aminoestrone, cinacalcet, and their analogues in excellent yields and selectivities, highlighting their potential application in pharmaceuticals.
TL;DR: The reactions described here enable access to the late-stage C-H mono- and bis-difluoromethylation for preparation of tool compounds for chemical biology and provide access to this hitherto untapped substituent for drug discovery.
Abstract: A technically simple procedure for direct C-H difluoromethylation of heteroaromatic compounds using off-the-shelf difluoroacetic acid as the difluoromethylating reagent has been developed. Mono-difluoromethylation versus bis-difluoromethylation is controlled as the result of the reaction temperature. The reactions described here enable access to the late-stage C-H mono- and bis-difluoromethylation for preparation of tool compounds for chemical biology and provide access to this hitherto untapped substituent for drug discovery
TL;DR: Rh(III)-catalyzed activation and acylation of sp3 C-H bonds has been realized with diarylcyclopropenone as an acylating reagent, providing enones in good yields under redox-neutral conditions.
TL;DR: In this article, the authors highlight that Cp2TiCl is a reagent widely used in radical and organometallic chemistry, which shows, if not all, at least some of the 12 principles summarized for Green Chemistry, such as waste minimization, catalysis, safer solvents, toxicity, energy efficiency, and atom economy.
TL;DR: In this article, the authors used ZnCl 2 to promote the rate of sodium borohydride (NaBH 4 ) hydrolysis in a hydrogen generation system to replace noble metal catalysts.