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Elisabetta Alberico, Alastair J J Lennox, Lydia K Vogt, Haijun Jiao, Wolfgang Baumann, Hans-Joachim Drexler, Martin Nielsen, Anke Spannenberg, Marek P Checinski, Henrik Junge, Matthias Beller
Ruthenium PNP complex 1a (RuH(CO)Cl(HN(C2H4Pi-Pr2)2)) represents a state-of-the-art catalyst for low-temperature (<100 °C) aqueous methanol dehydrogenation to H2 and CO2. Herein, we describe an investigation that combines experiment, spectroscopy and theory to provide a mechanistic rationale for this process. During catalysis, the presence of two anionic resting states was revealed, Ru-dihydride (3-) and Ru-monohydride (4-) that are deprotonated at nitrogen in the pincer ligand backbone. DFT calculations showed that O- and CH- coordination modes of methoxide to ruthenium compete, and form complexes 4- and 3-, respectively...
October 19, 2016: Journal of the American Chemical Society
Shogo Okumura, Shu-Wei Tang, Teruhiko Saito, Kazuhiko Semba, Shigeyoshi Sakaki, Yoshiaki Nakao
We report a method that ensures the selective alkylation of benzamides and aromatic ketones at the para-position via cooperative nickel/aluminum catalysis. Using a bulky catalyst/co-catalyst system allows reactions between benzamides with alkenes to afford the corresponding para-alkylated products. The origin of the high para-selectivity has also been investigated by density functional theory calculations.
October 19, 2016: Journal of the American Chemical Society
Feng Hu, Hongchao Yang, Changhong Wang, Yejun Zhang, Huan Lu, Qiangbin Wang
Rational design of cost-effective, nonprecious metal-based catalysts with desirable oxygen reduction reaction (ORR) performance is extremely important for future fuel cell commercialization, etc. Herein, a new type of ORR catalyst of Co-N-doped mesoporous carbon hollow sphere (Co-N-mC) was developed by pyrolysis from elaborately fabricated polystyrene@polydopamine-Co precursors. The obtained catalysts with active Co sites distributed in highly graphitized mesoporous N-doped carbon hollow spheres exhibited outstanding ORR activity with an onset potential of 0...
October 18, 2016: Small
Ek Raj Baral, Kavita Sharma, Muhammad Saeed Akhtar, Yong Rok Lee
A highly efficient and facile thermal multicomponent cascade reaction of readily available 4-oxo-4H-chromene-3-carbaldehydes with cyanoacetates or cyanoamides and anilines or aliphatic amines under solvent and catalyst-free conditions was developed for the synthesis of a range of polysubstituted 2-aminopyridine derivatives in good to excellent yield. This protocol proceeds via a cascade reaction of Knoevenagel condensation, nucleophilic addition, intramolecular Michael addition, and ring opening. As an application of this methodology, the antibacterial activities of some of the synthetic compounds were evaluated...
October 18, 2016: Organic & Biomolecular Chemistry
Satavisha Kayal, Santanu Mukherjee
Cascade Michael/cyclization reactions between 3-isothiocyanato oxindoles and exocyclic α,β-unsaturated ketones are shown to proceed efficiently in the presence of a quinine-derived tertiary amino-squaramide catalyst and furnish 3,2'-pyrrolidinyl bispirooxindoles containing two spiro-quaternary and three contiguous stereocenters as a single diastereomer with excellent enantioselectivities (up to 99 : 1 er).
October 18, 2016: Organic & Biomolecular Chemistry
Guang-Lin Zhang, Sheng Wang, Jin-Le Hou, Chong-Jiao Mo, Chen-Jie Que, Qin-Yu Zhu, Jie Dai
Although a lot of titanium oxo-clusters (TOCs) have been synthesized and characterized, research studies on their application properties are still limited. The work described here is not only aimed at the synthesis and crystal structures of the TOCs, but also aimed at exploration of their potential applications in molecule based fluorescence labelling and photocatalysis. Three heterometallic TOC compounds with lanthanide (Ln) elements Sm(iii) (1), Eu(iii) (2) and Gd(iii) (3) are prepared and their cluster structures are characterized as LnTi11 cages...
October 18, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Nicoleta Petrea, Răzvan Petre, Gabriel Epure, Vasile Şomoghi, Liviu C Tănase, Cristian M Teodorescu, Ştefan Neaţu
We report the applicability of a hybrid system comprising a La(3+)-based catalyst and an Au/TiO2 photocatalyst in the decomposition of chemical weapons. This system is able to perform complete degradation of soman, sarin and VX in less than 1 minute under low basic conditions and visible light irradiation.
October 18, 2016: Chemical Communications: Chem Comm
Lequan Liu, Feng Zhou, Rajesh Kodiyath, Shigenori Ueda, Hideki Abe, Defa Wang, Youquan Deng, Jinhua Ye
CO poisoning of Pt catalysts is one of the major challenges to the commercialization of proton exchange membrane fuel cells. One promising solution is to develop CO-tolerant Pt-based catalysts. A facilely synthesized Pt/FeOx catalyst exhibited outstanding CO tolerance in the oxidation of H2 and electrochemical CO stripping. Light-off temperature of H2O formation over Pt/FeOx was achieved even below 30 °C in the presence of 3000 ppm CO at a space velocity of 18 000 mL g(-1)cat h(-1). For the electrochemical oxidation of CO, the onset and peak potentials decreased by 0...
October 18, 2016: Physical Chemistry Chemical Physics: PCCP
Young Jin Sa, Dong-Jun Seo, Jinwoo Woo, Jung Tae Lim, Jae Yeong Cheon, Seung Yong Yang, Jae Myeong Lee, Dongwoo Kang, Tae Joo Shin, Hyeon Suk Shin, Hu Young Jeong, Chul Sung Kim, Min Gyu Kim, Tae-Young Kim, Sang Hoon Joo
Iron-nitrogen on carbon (Fe-N/C) catalysts have emerged as promising non-precious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in energy conversion and storage devices. It has been widely suggested that an active site structure for Fe-N/C catalysts contains Fe-Nx coordination. However, the preparation of high-performance Fe-N/C catalysts mostly involves a high-temperature pyrolysis step, which generates not only catalytically active Fe-Nx sites, but also less active large iron-based particles...
October 18, 2016: Journal of the American Chemical Society
Tobias F Berto, Kai E Sanwald, J Paige Byers, Nigel D Browning, Oliver Yair Gutiérrez Tinoco, Johannes A Lercher
Photocatalytic overall water splitting requires co-catalysts, which efficiently promote the generation of H2, but do not catalyze its reverse oxidation. We demonstrate, that CO chemisorbed on metal co-catalysts (Rh, Pt, Pd) suppresses the back reaction, while maintaining the rate of H2 evolution. On Rh/GaN:ZnO, the highest H2 production rates were obtained with 4 - 40 mbar CO, the back reaction remaining suppressed below 7 mbar O2. The O2 and H2 evolution rates compete with CO oxidation and the back reaction...
October 17, 2016: Journal of Physical Chemistry Letters
Xin Zhang, Ruyan Wu, Zeyi Wang, Mingxia Gao, Hongge Pan, Yongfeng Liu
Sodium alanate (NaAlH4) has attracted intense interest as a prototypical high-density hydrogen storage material. However, poor reversibility and slow kinetics limit its practical applications. In this work, a nanocrystalline ZrO2@C catalyst is synthesized using Uio-66(Zr) as a precursor and furfuryl alcohol (FA) as a carbon source. The as-synthesized ZrO2@C exhibits good catalytic activity for dehydrogenation and hydrogenation of NaAlH4. The NaAlH4-7 wt% ZrO2@C sample releases hydrogen starting from 126 °C and re-absorbs starting from 54 °C, and these temperatures are reduced by 71 °C and 36 °C, respectively, relative to those of pristine NaAlH4...
October 17, 2016: Chemistry, An Asian Journal
Yassine Oumellal, Karine Provost, Camelia Matei Ghimbeu, Alicia Martinez de Yuso, Claudia Zlotea
In-depth clarification of hydrogen interaction with noble metal nanoparticles and nanoalloys is essential for further development and design of efficient catalysts and hydrogen storage nanomaterials. This issue becomes even more challenging for nanoalloys of bulk-immiscible metals. The hydrogen interaction with bulk-immiscible Pd-Rh nanoalloys (3-6 nm) supported on mesoporous carbon is studied by both laboratory and large scale facility techniques. X-ray diffraction (XRD) reveals a single phase fcc structure for all nanoparticles confirming the formation of nanoalloys in the whole composition range...
October 17, 2016: Nanotechnology
Shibing Chu, Emanuele Coccia, Matteo Barborini, Leonardo Guidoni
Electron correlation plays a crucial role in the energetics of reactions catalyzed by transition metal complexes, such as water splitting. In the present work we exploit the performance of various methods to describe the thermodynamics of a simple but representative model of water splitting reaction, based on a single cobalt ion as catalyst. Density Functional Theory (DFT) calculations show a significant dependance on the the adopted functional and not negligible differences with respect to CSSD(T) findings are found along the reaction cycle...
October 17, 2016: Journal of Chemical Theory and Computation
Pavel Golubev, Ekaterina A Karpova, Alena S Pankova, Mariia Sorokina, Mikhail A Kuznetsov
Condensation of enynones readily available from cheap starting material with pyrazolamines provides easy access to fluorescent 7-(trimethylsilylethynyl)pyrazolo[1,5-a]pyrimidines. The reaction is straightforward, does not require the use of any additional reagents or catalysts and can be performed without inert atmosphere. Various substituents and functional groups in both enynone and pyrazolamine are tolerated. The presented method features full regioselectivity, high isolated yields and simplicity of both set-up and product purification...
October 17, 2016: Journal of Organic Chemistry
Brandon A Vara, Jeffrey N Johnston
Preparation of a range of enantioenriched β-fluoro amines (α,β-disubstituted) is described in which the nitrogen and fluorine atoms are attached to sp(3)-hybridized carbons. The key finding is a chiral bifunctional Brønsted acid/base catalyst that can deliver β-amino-α-fluoro nitroalkanes with high enantio- and diastereoselection. A denitration step renders the nitro group "traceless" and delivers secondary, tertiary, or vinyl alkyl fluorides embedded within a vicinal fluoro amine functional group. A synthesis of each possible stereoisomer of a β-fluoro lanicemine illustrates the potential ease with which fluorinated small molecules relevant to neuroscience drug development can be prepared in a stereochemically comprehensive manner...
October 17, 2016: Journal of the American Chemical Society
Fan Wang, Shuyan Song, Kai Li, Junqi Li, Jing Pan, Shuang Yao, Xin Ge, Jing Feng, Xiao Wang, Hongjie Zhang
A green and cost-effective method, named the "solid dual-ions-transformation reaction", is reported to achieve the goal of successfully doping S and N into hollow carbon nanotubes. No harmful raw material is needed during the whole synthesis. Importantly, in the catalytic test of chemical reduction of p-nitrophenol by NaBH4 , the as-obtained S,N co-doped hollow carbon nanotubes exhibit ultrahigh catalytic performances.
October 17, 2016: Advanced Materials
Claudia Weilbeer, Marcel Sickert, Sergej Naumov, Christoph Schneider
We disclose herein the first enantioselective aza-Diels-Alder reaction of b-alkyl-substituted vinylketene silyl-O,O-acetals and imines furnishing a broad range of optically highly enriched 4-alkyl-substituted 2-piperidones. As catalyst for this one-pot reaction we employed a chiral phosphoric acid which effects a vinylogous Mannich reaction directly followed by ring-closure to the lactam. Subsequent fully diastereoselective transformations including hydrogenation, enolate alkylation, and lactam alkylation/reduction processes converted the cycloadducts into various highly substituted piperidines of great utility for the synthesis of natural products and medicinally active compounds...
October 17, 2016: Chemistry: a European Journal
J M Stubbs, J-P J Bow, R J Hazlehurst, J M Blacquiere
The first successful use of the P(R)2N(R')2 (1,5-R'-3,7-R-1,5-diaza-3,7-diphosphacyclooctane) ligand family toward an organic synthesis is described. The precatalysts [Ru(Cp)(P(R)2N(Bn)2)(MeCN)]PF6 are active toward cyclization of 2-ethynylbenzyl alcohol at low catalyst loading and mild temperatures. Catalyst performance however is limited by both low conscription and by competitive deactivation.
October 17, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
S Vichaphund, V Sricharoenchaikul, D Atong
Fly ash-derived HZSM-5 catalyst was first applied in the catalytic pyrolysis of Jatropha residues in a semi-continuous fixed-bed reactor. The catalytic performance of HZSM-5 catalysts prepared from chemicals including conventional hydrothermal HZSM-5, Ni/HZSM-5 by ion exchange, and commercial HZSM-5 (Si/Al = 30) was evaluated for comparison. Catalytic pyrolysis of Jatropha residues with HZSM-5 catalysts was investigated in terms of product yields and qualities of bio-oil and bio-char. The liquid yield produced from fly ash-derived HZSM-5 was 29...
October 17, 2016: Environmental Technology
Zhiyong Bai, Qi Yang, Jianlong Wang
In this paper, Fe3O4/multi-wall carbon nanotubes composites were prepared, characterized and used as a catalyst for enhancing the ozonation of dimethyl phthalate (DMP) in aqueous solution. The experimental results showed that DMP degradation and mineralization increased by 26% and 20%, respectively, in catalytic ozonation compared with single ozonation, and more H2O2 and organic acids were produced during catalytic ozonation process than single ozonation. The effect of pH, ozone concentration and catalyst dosage on DMP degradation was determined...
October 17, 2016: Environmental Technology
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