Showing papers on "Reagent published in 2015"
TL;DR: Kinetics and computational studies suggested that the high amidating reactivity of 1,4,2-dioxazol-5-one can also be attributed to the low activation energy of an imido-insertion process in addition to the high coordination ability.
Abstract: Mechanistic investigations on the Cp*Rh(III)-catalyzed direct C–H amination reaction led us to reveal the new utility of 1,4,2-dioxazol-5-one and its derivatives as highly efficient amino sources. Stepwise analysis on the C–N bond-forming process showed that competitive binding of rhodium metal center to amidating reagent or substrate is closely related to the reaction efficiency. In this line, 1,4,2-dioxazol-5-ones were observed to have a strong affinity to the cationic Rh(III) giving rise to dramatically improved amidation efficiency when compared to azides. Kinetics and computational studies suggested that the high amidating reactivity of 1,4,2-dioxazol-5-one can also be attributed to the low activation energy of an imido-insertion process in addition to the high coordination ability. While the characterization of a cationic Cp*Rh(III) complex bearing an amidating reagent was achieved, its facile conversion to an amido-inserted rhodacycle allowed for a clear picture on the C–H amidation process. The ne...
328 citations
TL;DR: A general and benign iron-catalyzed α-alkylation reaction of ketones with primary alcohols has been developed and using 2-aminobenzyl alcohol as alkylation reagent allows for the "green" synthesis of quinoline derivatives.
Abstract: A general and benign iron-catalyzed α-alkylation reaction of ketones with primary alcohols has been developed. The key to success of the reaction is the use of a Knolker-type complex as catalyst (2 mol %) in the presence of Cs2 CO3 as base (10 mol %) under hydrogen-borrowing conditions. Using 2-aminobenzyl alcohol as alkylation reagent allows for the "green" synthesis of quinoline derivatives.
208 citations
TL;DR: The use of the mild aluminum reagent prevents undesired reduction of iron and allows the reaction to proceed with catalyst turnover numbers as high as 6500.
Abstract: Conversion of a C(sp2)–H or C(sp3)–H bond to the corresponding C–Me bond can be achieved by using AlMe3 or its air-stable diamine complex in the presence of catalytic amounts of an inorganic iron(III) salt and a diphosphine along with 2,3-dichlorobutane as a stoichiometric oxidant. The reaction is applicable to a variety of amide substrates bearing a picolinoyl or 8-aminoquinolyl directing group, enabling methylation of a variety of (hetero)aryl, alkenyl, and alkyl amides. The use of the mild aluminum reagent prevents undesired reduction of iron and allows the reaction to proceed with catalyst turnover numbers as high as 6500.
199 citations
TL;DR: An inexpensive, thermally stable deoxyfluorination reagent is reported that fluorinates a broad range of alcohols without substantial formation of elimination side products and enables deoxy fluorination on preparatory scale.
Abstract: We report an inexpensive, thermally stable deoxyfluorination reagent that fluorinates a broad range of alcohols without substantial formation of elimination side products. This combination of selectivity, safety, and economic viability enables deoxyfluorination on preparatory scale. We employ the [18F]-labeled reagent in the first example of a no-carrier-added deoxy-radiofluorination.
187 citations
TL;DR: An N-glycan labeling reagent is developed that provides enhanced fluorescence response and MS sensitivity for glycan detection and the process of preparing a sample for analysis is simplified and combined with UHPLC HILIC chromatography and high sensitivity mass spectrometry to thoroughly detail the N- glycan profile of a monoclonal antibody.
Abstract: N-glycosylation of proteins is now routinely characterized and monitored because of its significance to the detection of disease states and the manufacturing of biopharmaceuticals. At the same time, hydrophilic interaction chromatography (HILIC) has emerged as a powerful technology for N-glycan profiling. Sample preparation techniques for N-glycan HILIC analyses have however tended to be laborious or require compromises in sensitivity. To address these shortcomings, we have developed an N-glycan labeling reagent that provides enhanced fluorescence response and MS sensitivity for glycan detection and have also simplified the process of preparing a sample for analysis. The developed labeling reagent rapidly reacts with glycosylamines upon their release from glycoproteins. Within a 5 min reaction, enzymatically released N-glycans are labeled with this reagent comprised of an NHS-carbamate reactive group, a quinoline fluorophore, and a tertiary amine for enhancing ESI+ MS ionization. To further expedite the r...
175 citations
TL;DR: Using the widely available DMSO as the formylation reagent under oxidative conditions, an efficient Cu-catalyzed C3-formylation reaction of imidazo[1,2-a]pyridine C-H bonds to directly generate structurally sophisticated 3- formyl imidaz[ 1, 2-a], 1-a-Pyridine derivatives has been developed.
167 citations
Patent•
25 Feb 2015
TL;DR: In this paper, the authors present methods of forming SiC/SiCN film layers on surfaces of semiconductor substrates, which may include introducing a silicon-containing film-precursor and an organometallic ligand transfer reagent into a processing chamber.
Abstract: Disclosed herein are methods of forming SiC/SiCN film layers on surfaces of semiconductor substrates. The methods may include introducing a silicon-containing film-precursor and an organometallic ligand transfer reagent into a processing chamber, adsorbing the silicon-containing film-precursor, the organometallic ligand transfer reagent, or both onto a surface of a semiconductor substrate under conditions whereby either or both form an adsorption-limited layer, and reacting the silicon-containing film-precursor with the organometallic ligand transfer reagent, after either or both have formed the adsorption-limited layer. The reaction results in the forming of the film layer. In some embodiments, a byproduct is also formed which contains substantially all of the metal of the organometallic ligand transfer reagent, and the methods may further include removing the byproduct from the processing chamber. Also disclosed herein are semiconductor processing apparatuses for forming SiC/SiCN film layers.
162 citations
TL;DR: The first example of a practical and direct trifluoromethylthiolation reaction of unactivated aliphatic CH bonds employs a silver-based reagent and is operationally simple, scalable, and proceeds under aqueous conditions in air.
Abstract: The first example of a practical and direct trifluoromethylthiolation reaction of unactivated aliphatic CH bonds employs a silver-based reagent. The reaction is operationally simple, scalable, and proceeds under aqueous conditions in air. Furthermore, its broad scope and good functional-group compatibility were demonstrated by applying this method to the selective trifluoromethylthiolation of natural products and natural-product derivatives.
147 citations
TL;DR: This reaction represents the first hypervalent-iodine-enabled radical decarboxylative alkenylation reaction, and a novel benziodoxole-vinyl carboxylic acid reaction intermediate was isolated.
Abstract: Chemoselective C(sp(3))-C(sp(2)) coupling reactions under mild reaction conditions are useful for synthesizing alkyl-substituted alkenes having sensitive functional groups. Reported here is a visible-light-induced chemoselective alkenylation through a deboronation/decarboxylation sequence under neutral aqueous reaction conditions at room temperature. This reaction represents the first hypervalent-iodine-enabled radical decarboxylative alkenylation reaction, and a novel benziodoxole-vinyl carboxylic acid reaction intermediate was isolated. This C(sp(3))-C(sp(2)) coupling reaction leads to aryl-and acyl-substituted alkenes containing various sensitive functional groups. The excellent chemoselectivity, stable reactants, and neutral aqueous reaction conditions of the reaction suggest future biomolecule applications.
140 citations
TL;DR: Calculated molecular weights, lipophilicities, and polar surface areas are presented, demonstrating the utility of the method for delivering sulfonamides with drug-like properties.
Abstract: We describe a method for the synthesis of sulfonamides through the combination of an organometallic reagent, a sulfur dioxide equivalent, and an aqueous solution of an amine under oxidative conditions (bleach). This simple reaction protocol avoids the need to employ sulfonyl chloride substrates, thus removing the limitation imposed by the commercial availability of these reagents. The resultant method allows access to new chemical space, and is also tolerant of the polar functional groups needed to impart favorable physiochemical properties required for medicinal chemistry and agrochemistry. The developed chemistry is employed in the synthesis of a targeted 70 compound array, prepared using automated methods. The array achieved a 93% success rate for compounds prepared. Calculated molecular weights, lipophilicities, and polar surface areas are presented, demonstrating the utility of the method for delivering sulfonamides with drug-like properties.
129 citations
TL;DR: A simplified electrophilic trifluoromethylthiolating reagent 1c was identified that can react with a wide range of nucleophiles such as Grignard reagents, arylboronic acids, alkynes, indoles, β-ketoesters, oxindoles, and sodium sulfinates under mild reaction conditions.
Abstract: A family of electrophilic trifluoromethanesulfenates was prepared Structure–reactivity relationship studies showed that the substituted groups on the aryl ring of the trifluoromethylthiolating reagent did not have an obvious influence on their reactivities A simplified electrophilic trifluoromethylthiolating reagent 1c was then identified that can react with a wide range of nucleophiles such as Grignard reagents, arylboronic acids, alkynes, indoles, β-ketoesters, oxindoles, and sodium sulfinates under mild reaction conditions A variety of functional groups were tolerated under these conditions
TL;DR: A new, electrophilic difluoromethylthiophthalimide 3 was developed that allows the diffluorometHylthiolation of a wide range of nucleophiles including aryl/vinyl boronic acids, alkynes, amines, thiols, β-ketoesters, and oxindoles and electron-rich heteroarenes.
Abstract: A new, electrophilic difluoromethylthiolating reagent N-difluoromethylthiophthalimide 3 was developed. Reagent 3 can be readily synthesized in four steps from easily available starting materials phthalimide and TMSCF2H. N-difluoromethylthiophthalimide 3 is a powerful electrophilic difluoromethylthiolating reagent that allows the difluoromethylthiolation of a wide range of nucleophiles including aryl/vinyl boronic acids, alkynes, amines, thiols, β-ketoesters, and oxindoles and electron-rich heteroarenes such as indole, pyrrole, 1H-pyrrolo[2,3-b]pyridine, imidazo[1,2-a]pyridine, aminothiazole, isoxazole, and pyrazole under mild conditions.
TL;DR: A novel approach to agrochemically important difluoromethyl-substituted pyrazoles has been developed based on the elusive reagent CF2 HCHN2, which was synthesized for the first time and employed in [3+2] cycloaddition reactions with alkynes.
Abstract: A novel approach to agrochemically important difluoromethyl-substituted pyrazoles has been developed based on the elusive reagent CF2HCHN2, which was synthesized (generated in situ) for the first time and employed in [3+2] cycloaddition reactions with alkynes. The reaction is extremely practical as it is a one-pot process, does not require a catalyst or the isolation of the potentially toxic and explosive gaseous intermediate, and proceeds in a common solvent, namely chloroform, in air. The reaction is also scalable and allows for the preparation of the target pyrazoles on gram scale.
TL;DR: In this article, the chemical oxidation of benzene by Fe2+-catalyzed sodium percarbonate (SPC) was conducted, and the effects of various factors, such as the SPC/Fe2+/benzene molar ratio, temperature, order of the reagent addition, solution matrix including the presence of anions (Cl−, HCO3−, SO42− and NO3−), and the initial solution pH, were thoroughly investigated.
TL;DR: The first catalytic enantio- and diastereoselective synthesis of 1,2-hydroxyboronates is reported, and Mechanistic experiments indicate control of absolute stereochemistry of the α-boryl component.
Abstract: The first catalytic enantio- and diastereoselective synthesis of 1,2-hydroxyboronates is reported. Reactions are promoted by a readily available chiral monodentate phosphoramidite–copper complex in the presence of an alkyl 1,1-diboron reagent. Products contain two contiguous stereogenic centers and are obtained in up to 91% yield, >98:2 d.r., and 98:2 e.r. The reaction is tolerant of aryl and vinyl aldehydes, and the 1,2-hydroxyboronate products can be transformed into versatile derivatives. Mechanistic experiments indicate control of absolute stereochemistry of the α-boryl component.
TL;DR: Control experiments revealed that the presence of a sp(2) nitrogen atom at the 2-position of the substrate and the use of a boron-based reagent were crucial for the activation of the relatively inert C(aryl)-O bond of aryl 2-pyridyl ethers.
Abstract: The rhodium-catalyzed reaction of aryl 2-pyridyl ethers with a diboron reagent results in the formation of arylboronic acid derivatives via activation of the C(aryl)–O bonds. The straightforward synthesis of 1,2-disubstituted arenes was enabled through catalytic ortho C–H bond functionalization directed by the 2-pyridyloxy group followed by substitution of this group with a boryl group. Several control experiments revealed that the presence of a sp2 nitrogen atom at the 2-position of the substrate and the use of a boron-based reagent were crucial for the activation of the relatively inert C(aryl)–O bond of aryl 2-pyridyl ethers.
TL;DR: In this article, a uniform water-soluble monolayer MoS2 quantum dots (MQDs) with lateral sizes of ≈21 nm, a clearly zigzag-terminated edge, and a hexagonal lattice structure are achieved using ammonium molybdate, thiourea, and N-acetyl-l-cysteine (NAC) as precursors and the capping reagent in a facile one-pot hydrothermal approach.
Abstract: Uniform water-soluble monolayer MoS2 quantum dots (MQDs) with lateral sizes of ≈21 nm, a clearly zigzag-terminated edge, and a hexagonal lattice structure are achieved using ammonium molybdate, thiourea, and N-acetyl-l-cysteine (NAC) as precursors and the capping reagent in a facile one-pot hydrothermal approach MQDs have good dispersity and high stability in aqueous suspension and exhibit a significantly larger direct bandgap (396 eV) compared to monolayer MoS2 nanosheets (189 eV) Pronounced blue-shifts in the wavelengths of both the excitonic absorption and intrinsic state emission with activated strong luminescence at room temperature beyond monolayer MoS2 nanosheets is demonstrated Unusual upconversion photoluminescence is also observed and is caused by two successive transfers of energy from the near-infrared (NIR) absorption generated by the NAC capping reagent to the hexagonal structure of MQDs Additional optical properties of MQDs may provide numerous exciting technological applications Here, MQDs are demonstrated as a highly selective fluorescent reagent for detecting tetracycline hydrochloride under UV and NIR irradiation
TL;DR: Attempts to use nitrous oxide (N2O, 'laughing gas') as a reagent in synthetic chemistry are summarized, it is shown that N2O can be used as an N-atom donor for the synthesis of interesting organic molecules such as triazenes and azo dyes.
Abstract: This review article summarizes efforts to use nitrous oxide (N2O, ‘laughing gas’) as a reagent in synthetic chemistry. The focus will be on reactions which are carried out in homogeneous solution under (relatively) mild conditions. First, the utilization of N2O as an oxidant is discussed. Due to the low intrinsic reactivity of N2O, selective oxidation reactions of highly reactive compounds are possible. Furthermore, it is shown that transition metal complexes can be used to catalyze oxidation reactions, in some cases with high turnover numbers. In the final part of this overview, the utilization of N2O as a building block for more complex molecules is discussed. It is shown that N2O can be used as an N-atom donor for the synthesis of interesting organic molecules such as triazenes and azo dyes.
TL;DR: The results indicated that the specific resistance to filterability (SRF) of sludge was reduced efficiently by approximately 90%, when conditioned with Fenton's reagent and lime, and the economic assessment shows that Fenton’s re agent and lime combined with ultrahigh pressure filtration system can be an economical and viable technology for sewage sludge dewatering.
TL;DR: It was concluded that the (NFC-MAA-MA) aerogel may be used as a high capacity and reusable sorbent material in heavy-metal removing processes.
TL;DR: The results indicate that the reaction proceeds at the hypervalent iodine moiety of Togni reagent, which is activated by Cu(II) species acting as a Lewis acid catalyst, and this transformation exhibited a remarkable rate enhancement upon addition of Et3N.
Abstract: We examined the mechanism of our previously reported aminotrifluoromethylation reaction, which proceeds via intramolecular cyclization of alkenylamines in the presence of the combination of copper catalyst and Togni reagent (1). Kinetic studies revealed that the initial rate of the reaction was first order with respect to Togni reagent and CuI, as well as the substrate. Changes of the 19F NMR chemical shift of Togni reagent during the reaction suggested the existence of a dynamic equilibrium involving coordination of not only Togni reagent, but also the substrate amine and the product aziridine to copper. ESI-MS analysis provided evidence of involvement of reactive Cu(II) intermediates in the catalytic cycle. Overall, our results indicate that the reaction proceeds at the hypervalent iodine moiety of Togni reagent, which is activated by Cu(II) species acting as a Lewis acid catalyst. On the basis of these mechanistic considerations, we developed an efficient synthesis of trifluoromethylated pyrrolidine de...
TL;DR: In this article, a modified version of amine transfer reagent was proposed for the synthesis of chiral secondary amines using a variety of coupling partners, including those derived from amino acid esters, carbohydrates, and steroids.
Abstract: The CuH-catalyzed hydroamination of alkenes and alkynes using a silane and an amine transfer reagent represents a simple strategy to access chiral amine products. We have recently reported methods to prepare chiral amines with high efficiency and stereoselectivity using this approach. However, the current technology is limited to the synthesis of trialkylamines from dialkylamine transfer reagents (R2NOBz). When monoalkylamine transfer reagents [RN(H)OBz] were used for the synthesis of chiral secondary amines, competitive, nonproductive consumption of these reagents by the CuH species resulted in poor yields. In this paper, we report the design of a modified type of amine transfer reagent that addresses this limitation. This effort has enabled us to develop a CuH-catalyzed synthesis of chiral secondary amines using a variety of amine coupling partners, including those derived from amino acid esters, carbohydrates, and steroids. Mechanistic investigations indicated that the modified amine transfer reagents ...
TL;DR: A palladium-catalyzed, norbornene-mediated Catellani ortho-acylation reaction was developed by the use of either acyl chlorides or acid anhydrides as acylation reagents.
Abstract: A palladium-catalyzed, norbornene-mediated Catellani ortho-acylation reaction was developed by the use of either acyl chlorides or acid anhydrides as acylation reagents. The addition of more than a stoichiometric amount of H2 O is crucial for this transformation when acid chlorides are used, and kinetic studies indicate that the active acylation reagent is possibly an acid anhydride.
TL;DR: A metal-free small molecule catalyst is described that achieves the three component reaction between a homoallylic alcohol, carbon dioxide, and an electrophilic source of iodine and Cyclic carbonates are formed enantioselectively.
Abstract: Carbon dioxide exhibits many of the qualities of an ideal reagent: it is nontoxic, plentiful, and inexpensive. Unlike other gaseous reagents, however, it has found limited use in enantioselective synthesis. Moreover, unprecedented is a tool that merges one of the simplest biological approaches to catalysis—Bronsted acid/base activation—with this abundant reagent. We describe a metal-free small molecule catalyst that achieves the three component reaction between a homoallylic alcohol, carbon dioxide, and an electrophilic source of iodine. Cyclic carbonates are formed enantioselectively.
TL;DR: Kinetic and spectroscopic studies showed that the turnover-limiting step is regeneration of the CuH catalyst by reaction with a silane, with a phosphine-ligated copper(I) benzoate as the catalyst resting state, consistent with a monomeric active catalyst.
Abstract: Enantioselective copper(I) hydride (CuH)-catalyzed hydroamination has undergone significant development over the past several years. To gain a general understanding of the factors governing these reactions, kinetic and spectroscopic studies were performed on the CuH-catalyzed hydroamination of styrene. Reaction profile analysis, rate order assessment, and Hammett studies indicate that the turnover-limiting step is regeneration of the CuH catalyst by reaction with a silane, with a phosphine-ligated copper(I) benzoate as the catalyst resting state. Spectroscopic, electrospray ionization mass spectrometry, and nonlinear effect studies are consistent with a monomeric active catalyst. With this insight, targeted reagent optimization led to the development of an optimized protocol with an operationally simple setup (ligated copper(II) precatalyst, open to air) and short reaction times (<30 min). This improved protocol is amenable to a diverse range of alkene and alkyne substrate classes.
TL;DR: Three-component reaction of aryl Grignard reagents, alkynes, and aryal halides in the presence of 1 mol % of NiCl2 proceeded sequentially through carbomagnesiation of the alkyne followed by cross-coupling of the resulting alkenyl Grignards reagent with aryL halide to give tetrasubstituted alkenes in high yields.
Abstract: Three-component reaction of aryl Grignard reagents, alkynes, and aryl halides in the presence of 1 mol % of NiCl2 proceeded sequentially through carbomagnesiation of the alkyne followed by cross-coupling of the resulting alkenyl Grignard reagent with aryl halide to give tetrasubstituted alkenes in high yields.
TL;DR: The alkyl group in the boron reagent can be extended to primary alkyls, benzyl, and cycloalkyls, and the reaction proceeded with controllable mono- and dialkylation selectivity when both ortho C-H sites are accessible.
TL;DR: This reaction not only provides a new protocol for aryl C-H trifluoromethylation, but the generation of CF3· from TFA may prove useful in other contexts and could potentially be extended to other triffluorometHylation reactions.
TL;DR: An efficient and mild method for constructing C-S bonds compatible with various biomolecules including amino acids, oligosaccharides, nucleosides, proteins, and cell lysates is reported.
TL;DR: Application of a fluoroiodine analogue of the Togni reagent was studied in fluorocyclization reactions and has a very broad synthetic scope for preparation of functionalized hetero- and isocyclic compounds having a tertiary fluorine substituent.
Abstract: Application of a fluoroiodine analogue of the Togni reagent was studied in fluorocyclization reactions. In the presence of a transition-metal catalyst the applied fluoroiodine reagent can be used for aminofluorination, oxyfluorination, and carbofluorination reactions. The described procedure has a very broad synthetic scope for preparation of functionalized hetero- and isocyclic compounds having a tertiary fluorine substituent.