journal
MENU ▼
Read by QxMD icon Read
search

ACS Catalysis

journal
https://www.readbyqxmd.com/read/27840771/a-synthesis-of-substituted-%C3%AE-allenols-via-iron-catalyzed-cross-coupling-of-propargyl-carboxylates-with-grignard-reagents
#1
Simon N Kessler, Fabian Hundemer, Jan-E Bäckvall
α-Allenols are attractive and versatile compounds whose preparation can be a nontrivial task. In this Letter, we provide a method for the prompt synthesis of substituted α-allenols via a catalytic cross-coupling reaction which makes use of a nontoxic and cost-effective iron catalyst. The catalyst loading is typically as low as 1-5 mol %. The mild reaction conditions (-20 °C) and the short reaction time (15 min) allow for the presence of a variety of functional groups. Moreover, the reaction was shown to be scalable up to gram-scale and the propargyl substrates are readily accessible by a one-pot synthesis...
November 4, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27761299/improving-formate-and-methanol-fuels-catalytic-activity-of-single-pd-coated-carbon-nanotubes
#2
Xiuting Li, Hannah Hodson, Christopher Batchelor-McAuley, Lidong Shao, Richard G Compton
The oxidations of formate and methanol on nitrogen-doped carbon nanotubes decorated with palladium nanoparticles were studied at both the single-nanotube and ensemble levels. Significant voltammetric differences were seen. Pd oxide formation as a competitive reaction with formate or methanol oxidation is significantly inhibited at high overpotentials under the high mass transport conditions associated with single-particle materials in comparison with that seen with ensembles, where slower diffusion prevails...
October 7, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27761298/palladium-catalyzed-oxidative-domino-carbocyclization-arylation-of-bisallenes
#3
Chandra M R Volla, Jan-E Bäckvall
Herein we report a highly efficient and site-selective palladium-catalyzed oxidative carbocyclization-arylation reaction of bisallenes and arylboronic acids under operationally simple conditions for the selective synthesis of cyclohexadiene derivatives. The palladium source and the solvent proved to be crucial for the selectivity and the reactivity displayed. Interestingly, in the absence of the nucleophile, an oxidative carbocyclization-β-elimination pathway predominates. The reaction conditions are compatible with a wide range of functional groups, and the reaction exhibits broad substrate scope...
October 7, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27747133/metal-catalyzed-carboxylation-of-organic-pseudo-halides-with-co2
#4
Marino Börjesson, Toni Moragas, Daniel Gallego, Ruben Martin
The recent years have witnessed the development of metal-catalyzed reductive carboxylation of organic (pseudo)halides with CO2 as C1 source, representing potential powerful alternatives to existing methodologies for preparing carboxylic acids, privileged motifs in a myriad of pharmaceuticals and molecules displaying significant biological properties. While originally visualized as exotic cross-coupling reactions, a close look into the literature data indicates that these processes have become a fertile ground, allowing for the utilization of a variety of coupling partners, even with particularly challenging substrate combinations...
October 7, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27818842/enhancement-of-the-hydrogen-evolution-reaction-from-ni-mos2-hybrid-nanoclusters
#5
Daniel Escalera-López, Yubiao Niu, Jinlong Yin, Kevin Cooke, Neil V Rees, Richard E Palmer
This report focuses on a novel strategy for the preparation of transition metal-MoS2 hybrid nanoclusters based on a one-step, dual-target magnetron sputtering, and gas condensation process demonstrated for Ni-MoS2. Aberration-corrected STEM images coupled with EDX analysis confirms the presence of Ni and MoS2 in the hybrid nanoclusters (average diameter = 5.0 nm, Mo:S ratio = 1:1.8 ± 0.1). The Ni-MoS2 nanoclusters display a 100 mV shift in the hydrogen evolution reaction (HER) onset potential and an almost 3-fold increase in exchange current density compared with the undoped MoS2 nanoclusters, the latter effect in agreement with reported DFT calculations...
September 2, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27668125/role-of-the-three-phase-boundary-of-the-platinum-support-interface-in-catalysis-a-model-catalyst-kinetic-study
#6
Evangelos I Papaioannou, Christoph Bachmann, Jonas J Neumeier, Daniel Frankel, Herbert Over, Juergen Janek, Ian S Metcalfe
A series of microstructured, supported platinum (Pt) catalyst films (supported on single-crystal yttria-stabilized zirconia) and an appropriate Pt catalyst reference system (supported on single-crystal alumina) were fabricated using pulsed laser deposition and ion-beam etching. The thin films exhibit area-specific lengths of the three-phase boundary (length of three-phase boundary between the Pt, support, and gas phase divided by the superficial area of the sample) that vary over 4 orders of magnitude from 4...
September 2, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27563493/correlating-calmodulin-landscapes-with-chemical-catalysis-in-neuronal-nitric-oxide-synthase-using-time-resolved-fret-and-a-5-deazaflavin-thermodynamic-trap
#7
Tobias M Hedison, Nicole G H Leferink, Sam Hay, Nigel S Scrutton
A major challenge in enzymology is the need to correlate the dynamic properties of enzymes with, and understand the impact on, their catalytic cycles. This is especially the case with large, multicenter enzymes such as the nitric oxide synthases (NOSs), where the importance of dynamics has been inferred from a variety of structural, single-molecule, and ensemble spectroscopic approaches but where motions have not been correlated experimentally with mechanistic steps in the reaction cycle. Here we take such an approach...
August 5, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27398262/palladium-catalyzed-enantioselective-heine-reaction
#8
Molly Punk, Charlotte Merkley, Katlyn Kennedy, Jeremy B Morgan
Aziridines are important synthetic intermediates for the generation of nitrogen-containing molecules. N-Acylaziridines undergo rearrangement by ring expansion to produce oxazolines, a process known as the Heine reaction. The first catalytic, enantioselective Heine reaction is reported for meso-N-acylaziridines where a palladium(II)-diphosphine complex is employed. The highly enantioenriched oxazoline products are valuable organic synthons and potential ligands for transition-metal catalysis.
July 1, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27398261/building-bridges-biocatalytic-c-c-bond-formation-toward-multifunctional-products
#9
Nina G Schmidt, Elisabeth Eger, Wolfgang Kroutil
Carbon-carbon bond formation is the key reaction for organic synthesis to construct the carbon framework of organic molecules. The review gives a selection of biocatalytic C-C-bond-forming reactions which have been investigated during the last 5 years and which have already been proven to be applicable for organic synthesis. In most cases, the reactions lead to products functionalized at the site of C-C-bond formation (e.g., α-hydroxy ketones, aminoalcohols, diols, 1,4-diketones, etc.) or allow to decorate aromatic and heteroaromatic molecules...
July 1, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27330847/size-and-promoter-effects-on-stability-of-carbon-nanofiber-supported-iron-based-fischer-tropsch-catalysts
#10
Jingxiu Xie, Hirsa M Torres Galvis, Ard C J Koeken, Alexey Kirilin, A Iulian Dugulan, Matthijs Ruitenbeek, Krijn P de Jong
The Fischer-Tropsch Synthesis converts synthesis gas from alternative carbon resources, including natural gas, coal, and biomass, to hydrocarbons used as fuels or chemicals. In particular, iron-based catalysts at elevated temperatures favor the selective production of C2-C4 olefins, which are important building blocks for the chemical industry. Bulk iron catalysts (with promoters) were conventionally used, but these deactivate due to either phase transformation or carbon deposition resulting in disintegration of the catalyst particles...
June 3, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27807509/palladium-ii-catalyzed-annulation-between-ortho-alkenylphenols-and-allenes-key-role-of-the-metal-geometry-in-determining-the-reaction-outcome
#11
Noelia Casanova, Karina P Del Rio, Rebeca García-Fandiño, José L Mascareñas, Moisés Gulías
2-Alkenylphenols react with allenes, upon treatment with catalytic amounts of Pd(II) and Cu(II), to give benzoxepine products in high yields and with very good regio- and diastereoselectivities. This contrasts with the results obtained with Rh catalysts, which provided chromene-like products through a pathway involving a β-hydrogen elimination step. Computational studies suggest that the square planar geometry of the palladium is critical to favor the reductive elimination process required for the formation of the oxepine products...
May 6, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27453799/fib-sem-tomography-probes-the-mesoscale-pore-space-of-an-individual-catalytic-cracking-particle
#12
D A Matthijs de Winter, Florian Meirer, Bert M Weckhuysen
The overall performance of a catalyst particle strongly depends on the ability of mass transport through its pore space. Characterizing the three-dimensional structure of the macro- and mesopore space of a catalyst particle and establishing a correlation with transport efficiency is an essential step toward designing highly effective catalyst particles. In this work, a generally applicable workflow is presented to characterize the transport efficiency of individual catalyst particles. The developed workflow involves a multiscale characterization approach making use of a focused ion beam-scanning electron microscope (FIB-SEM)...
May 6, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27660732/highly-efficient-and-selective-hydrogenation-of-aldehydes-a-well-defined-fe-ii-catalyst-exhibits-noble-metal-activity
#13
Nikolaus Gorgas, Berthold Stöger, Luis F Veiros, Karl Kirchner
The synthesis and application of [Fe(PNP(Me)-iPr)(CO)(H)(Br)] and [Fe(PNP(Me)-iPr)(H)2(CO)] as catalysts for the homogeneous hydrogenation of aldehydes is described. These systems were found to be among the most efficient catalysts for this process reported to date and constitute rare examples of a catalytic process which allows selective reduction of aldehydes in the presence of ketones and other reducible functionalities. In some cases, TONs and TOFs of up to 80000 and 20000 h(-1), respectively, were reached...
April 1, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27076991/role-of-sn-in-the-regeneration-of-pt-%C3%AE-al2o3-light-alkane-dehydrogenation-catalysts
#14
Hien N Pham, Jesper J H B Sattler, Bert M Weckhuysen, Abhaya K Datye
Alumina-supported Pt is one of the major industrial catalysts for light alkane dehydrogenation. This catalyst loses activity during reaction, with coke formation often considered as the reason for deactivation. As we show in this study, the amount and nature of carbon deposits do not directly correlate with the loss of activity. Rather, it is the transformation of subnanometer Pt species into larger Pt nanoparticles that appears to be responsible for the loss of catalytic activity. Surprisingly, a portion of the Sn remains atomically dispersed on the alumina surface in the spent catalyst and helps in the redispersion of the Pt...
April 1, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27076990/nanoscale-chemical-imaging-of-an-individual-catalyst-particle-with-soft-x-ray-ptychography
#15
Anna M Wise, Johanna Nelson Weker, Sam Kalirai, Maryam Farmand, David A Shapiro, Florian Meirer, Bert M Weckhuysen
Understanding Fe deposition in fluid catalytic cracking (FCC) catalysis is critical for the mitigation of catalyst degradation. Here we employ soft X-ray ptychography to determine at the nanoscale the distribution and chemical state of Fe in an aged FCC catalyst particle. We show that both particle swelling due to colloidal Fe deposition and Fe penetration into the matrix as a result of precracking of large organic molecules occur. The application of ptychography allowed us to provide direct visual evidence for these two distinct Fe-based deactivation mechanisms, which have so far been proposed only on the basis of indirect evidence...
April 1, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27175308/diazafluorenone-promoted-oxidation-catalysis-insights-into-the-role-of-bidentate-ligands-in-pd-catalyzed-aerobic-aza-wacker-reactions
#16
Paul B White, Jonathan N Jaworski, Geyunjian Harry Zhu, Shannon S Stahl
2,2'-Bipyridine (bpy), 1,10-phenanthroline (phen) and related bidentate ligands often inhibit homogeneous Pd-catalyzed aerobic oxidation reactions; however, certain derivatives, such as 4,5-diazafluoren-9-one (DAF), can promote catalysis. In order to gain insight into this divergent ligand behavior, eight different bpy- and phen-derived chelating ligands have been evaluated in Pd(OAc)2-catalyzed oxidative cyclization of (E)-4-hexenyltosylamide. Two of the ligands, DAF and 6,6'-dimethyl-2,2'-bipyridine (6,6'-Me2bpy), support efficient catalytic turnover, while the others strongly inhibit the reaction...
March 11, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27563492/ruthenium-catalyzed-c-h-bond-activation-approach-to-azolyl-aminals-and-hemiaminal-ethers-mechanistic-evaluations-and-isomer-interconversion
#17
Manish K Singh, Hari K Akula, Sakilam Satishkumar, Lothar Stahl, Mahesh K Lakshman
C(sp(3))-N bond-forming reactions between benzotriazole and 5,6-dimethylbenzotriazole with N-methylpyrrolidinone, tetrahydrofuran, tetrahydropyran, diethyl ether, 1,4-dioxane, and isochroman have been conducted using RuCl3•3H2O/t-BuOOH in 1,2-dichloroethane. In all cases, N1 and N2 alkylation products were obtained, and these are readily separated by chromatography. One of these products, 1-(isochroman-1-yl)-5,6-dimethyl-1H-benzotriazole, was examined by X-ray crystallography. It is the first such compound to be analyzed by this method, and notably, the benzotriazolyl moiety is quasi-axially disposed, consistent with the anomeric effect...
March 4, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27274902/late-stage-diversification-of-biologically-active-molecules-via-chemoenzymatic-c-h-functionalization
#18
Landon J Durak, James T Payne, Jared C Lewis
Engineered variants of rebeccamycin halogenase were used to selectively halogenate a number of biologically active aromatic compounds. Subsequent Pd-catalyzed cross-coupling reactions on the crude extracts of these reactions were used to install aryl, amine, and ether substituents at the halogenation site. This simple, chemoenzymatic method enables non-directed functionalization of C-H bonds on a range of substrates to provide access to derivatives that would be challenging or inefficient to prepare by other means...
March 4, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27699088/efficient-benzimidazolidinone-synthesis-via-rhodium-catalyzed-double-decarbonylative-c-c-activation-cycloaddition-between-isatins-and-isocyanates
#19
Rong Zeng, Peng-Hao Chen, Guangbin Dong
The first decarbonylative cycloaddition of less-strained cyclic ketones (isatins) with isocyanates is reported. Initiated by C-C activation, this distinct [5-2+2] transformation provides a rapid entry to access various benzimidazolidinone derivatives, through which a wide range of isocyanates can be efficiently coupled with broad functional group tolerance. A modified one-pot process, combining Curtius rearrangement and C-C activation, was also achieved by using acyl azides as the starting materials. Detailed mechanistic study revealed a surprising double-decarbonylative reaction pathway...
February 5, 2016: ACS Catalysis
https://www.readbyqxmd.com/read/27525171/cobalt-catalyzed-aminoquinoline-directed-functionalization-of-phosphinic-amide-sp-2-c-h-bonds
#20
Tung Thanh Nguyen, Liene Grigorjeva, Olafs Daugulis
In this paper, we introduce arylphosphinic acid aminoquinoline amides as competent substrates for cobalt-catalyzed sp(2) C-H bond functionalization. Specifically, the feasibility of their coupling with alkynes, alkenes, and allyl pivalate has been demonstrated. Reactions are catalyzed by simple Co(NO3)2 hydrate in ethanol or mixed dioxane/tBuOH solvent in the presence of Mn(OAc)3·2H2O additive, sodium pivalate, or acetate base and use oxygen from the air as an oxidant. Directing group removal affords ortho-functionalized P,P-diarylphosphinic acids...
February 5, 2016: ACS Catalysis
journal
journal
43608
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"