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https://www.readbyqxmd.com/read/28538656/recent-advances-in-c-c-and-c-n-bond-forming-reactions-catalysed-by-polystyrene-supported-copper-complexes
#1
REVIEW
Pavel Drabina, Jan Svoboda, Miloš Sedlák
This present mini-review covers recently published results on Cu(I) and Cu(II) complexes immobilized on polystyrene carriers, which are used as heterogeneous, eco-friendly reusable catalysts applied for carbon-carbon and carbon-nitrogen forming reactions. Recent advances and trends in this area are demonstrated in the examples of oxidative homocoupling of terminal alkynes, the synthesis of propargylamines, nitroaldolization reactions, azide alkyne cycloaddition, N-arylation of nitrogen containing compounds, aza-Michael additions, asymmetric Friedel-Crafts reactions, asymmetric Mukaiyama aldol reactions, and asymmetric 1,3-dipolar cycloaddition of azomethine ylides...
May 24, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28537740/cationic-n-heterocyclic-carbene-copper-catalyzed-1-3-alkoxy-rearrangement-of-n-alkoxyanilines
#2
Itaru Nakamura, Takeru Jo, Yasuhiro Ishida, Hiroki Tashiro, Masahiro Terada
The [1,3]-alkoxy rearrangement reactions of N-alkoxyanilines were efficiently catalyzed by cationic N-heterocyclic carbene (NHC)-Cu catalysts in affording 2-alkoxyaniline derivatives in good to excellent yields with high functional group compatibility. For N-alkoxyanilines having an electron-withdrawing substituent at the meta-position, the alkoxy group selectively migrated to the more hindered ortho-position. In contrast, the alkoxy group migrated to the less hindered ortho-position for N-alkoxyanilines having an electron-donating substituent...
May 24, 2017: Organic Letters
https://www.readbyqxmd.com/read/28537724/palladium-catalyzed-enantioselective-arylation-of-aryl-sulfenate-anions-a-combined-experimental-and-computational-study
#3
Tiezheng Jia, Mengnan Zhang, Samuel P McCollom, Ana Bellomo, Sonia Montel, Jianyou Mao, Spencer D Dreher, Christopher J Welch, Erik L Regalado, R Thomas Williamson, Brian C Manor, Neil C Tomson, Patrick J Walsh
A novel approach to produce chiral diaryl sulfoxides from aryl benzyl sulfoxides and aryl bromides via an enantioselective arylation of aryl sulfenate anions is reported. A (JosiPhos)Pd-based catalyst successfully promotes the asymmetric arylation reaction with good functional group compatibility. A wide range of enantioenriched diaryl, aryl heteroaryl, and even diheteroaryl sulfoxides were generated. Many of the sulfoxides prepared herein would be difficult to prepare via classic enantioselective oxidation of sulfides, including Ph(Ph-d5)SO (90% ee, 95% yield)...
May 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28537723/multivariate-metal-organic-frameworks-as-multifunctional-heterogeneous-asymmetric-catalysts-for-a-broad-of-sequential-reactions
#4
Qingchun Xia, Zijian Li, Chunxia Tan, Yan Liu, Wei Gong, Yong Cui
The search for versatile heterogeneous catalysts with multiple active sites for a broad of asymmetric transformations has long been of great interest, but it remains a formidable synthetic challenge. Here we demonstrate that multivariate metal-organic frameworks (MTV-MOFs) can be used as an excellent platform to engineer heterogeneous catalysts featuring multiple and cooperative active sites. An isostructural series of twofold interpenetrated MTV-MOFs that contain up to three different chiral metallosalen catalysts were constructed and used as efficient and recyclable heterogeneous catalysts for a variety of asymmetric sequential alkene epoxidation/epoxide ring-opening reactions...
May 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28537722/a-novel-micro-mea-design-to-precisely-measure-the-in-situ-activity-of-orr-electrocatalysts-for-pemfc
#5
Zhi Long, Yankai Li, Guangrong Deng, Changpeng Liu, Junjie Ge, Shuhua Ma, Wei Xing
An in-situ micro-MEA technique, which could precisely measure the performance of ORR electrocatalyst using Nafion as electrolyte, was designed and compared with regular thin-film rotating-disk electrode (TFRDE) (0.1 M HClO4) and normal in-situ membrane electrode assembly (MEA) tests. Compared to the traditional TFRDE method, the micro-MEA technique makes the acquisition of catalysts' behavior at low potential values easily achieved without being limited by the solubility of O2 in water. At the same time, it successfully mimics the structure of regular MEAs and obtains similar results to a regular MEA, thus providing a new technique to simply measure the electrode activity without being bothered by complicated fabrication of regular MEA...
May 24, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28537721/multivariate-chiral-covalent-organic-frameworks-with-controlled-crystallinity-and-stability-for-asymmetric-catalysis
#6
Jie Zhang, Xing Han, Xiaowei Wu, Yan Liu, Yong Cui
The modular construction of covalent organic frameworks (COFs) provides a convenient platform for designing high-performance functional materials, but the synthetic control over their chirality has been relatively little attended. Here we report a multiple-component strategy to construct chiral COFs (CCOFs) with controlled crystallinity and stability for heterogeneous asymmetric catalysis. By crystallizing mixtures of triamines with and without chiral organocatalysts and a dialdehyde, a family of two- and three-component 2D porous CCOFs that adopt three different stacking modes is prepared...
May 24, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28537706/sodium-rivals-silver-as-single-atom-active-centers-for-catalyzing-abatement-of-formaldehyde
#7
Yaxin Chen, Jiayi Gao, Zhiwei Huang, Meijuan Zhou, Junxiao Chen, Chao Li, Zhen Ma, Jianmin Chen, Xingfu Tang
The development of efficient alkali-based catalysts for the abatement of formaldehyde (HCHO), a ubiquitous air pollutant, is economically desirable. Here we comparatively study the catalytic performance of two single-atom catalysts, Na1/HMO and Ag1/HMO (HMO = Hollandite manganese oxide), in the complete oxidation of HCHO at low temperatures, in which the products are only CO2 and H2O. These catalysts are synthesized by anchoring single sodium ions or silver atoms on HMO(001) surfaces. Synchrotron X-ray diffraction patterns with structural refinement together with transmission electron microscopy images demonstrate that single sodium ions on the HMO(001) surfaces of Na1/HMO have the same local structures as silver atoms of Ag1/HMO...
May 24, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28535344/clarifying-the-controversial-catalytic-performance-of-co-oh-2-and-co3o4-for-oxygen-reduction-evolution-reactions-toward-efficient-zn-air-batteries
#8
Zhishuang Song, Xiaopeng Han, Yida Deng, Naiqin Zhao, Wenbin Hu, Cheng Zhong
Cobalt-based nanomaterials have been widely studied as catalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) due to their remarkable bifunctional catalytic activity, low cost and easy available. However, controversial results concerning OER/ORR performance exist between different types of cobalt-based catalysts, especially for Co(OH)2 and Co3O4. To address this issue, we develop a facile electrochemical deposition method to grow Co(OH)2 directly on the skeleton of carbon cloth, and further Co3O4 was obtained by post thermal treatment...
May 23, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28534898/the-cubic-to-hexagonal-phase-transition-of-cerium-oxide-particles-dynamics-and-structure
#9
Jan Höcker, Jon-Olaf Krisponeit, Thomas Schmidt, Jens Falta, Jan Ingo Flege
Cerium oxide is often applied in today's catalysts due to its remarkable oxygen storage capacity. The changes in stoichiometry during reaction are linked to structural modifications, which in turn affect its catalytic activity. We present a real-time in situ study of the structural transformations of cerium oxide particles on ruthenium(0001) at high temperatures of 700 °C in ultra-high vacuum. Our results demonstrate that the reduction from CeO2 to cubic Ce2O3 proceeds via ordered intermediary phases. The final reduction step from cubic to hexagonal Ce2O3 is accompanied by a lattice expansion, the formation of two new surface terminations, a partial dissolution of the cerium oxide particles, and a massive mass transport of cerium from the particles to the substrate...
May 23, 2017: Nanoscale
https://www.readbyqxmd.com/read/28534629/synthetic-posttranslational-modifications-chemical-catalyst-driven-regioselective-histone-acylation-of-native-chromatin
#10
Yoshifumi Amamoto, Yuki Aoi, Nozomu Nagashima, Hiroki Suto, Daisuke Yoshidome, Yasuhiro Arimura, Akihisa Osakabe, Daiki Kato, Hitoshi Kurumizaka, Shigehiro A Kawashima, Kenzo Yamatsugu, Motomu Kanai
Posttranslational modifications (PTMs) of histones play an important role in the complex regulatory mechanisms governing gene transcription, and their dysregulation can cause diseases such as cancer. The lack of methods for site-selectively modifying native chromatin, however, limits our understanding of the functional roles of a specific histone PTM, not as a single mark, but in the intertwined PTM network. Here, we report a synthetic catalyst DMAP-SH (DSH), which activates chemically stable thioesters (including acetyl-CoA) under physiological conditions and transfers various acyl groups to the proximate amino groups...
May 23, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28534624/switchable-c-h-functionalization-of-n-tosyl-acrylamides-with-acryloylsilanes
#11
Shengjin Song, Ping Lu, Huan Liu, Sai-Hu Cai, Chao Feng, Teck-Peng Loh
A controllable Rh-catalyzed protocol to access alkylation and alkenylation-annulation of N-tosyl acrylamide with acryloyl silane is reported. In contrast to the directing group or catalyst-dependent divergent sp(2) C-H alkylation/alkenylation, the intrinsic property of acryloylsilane allows the switchable reaction manifold, thereby affording either alkylation or annulation products with slight modification of the reaction conditions.
May 23, 2017: Organic Letters
https://www.readbyqxmd.com/read/28534611/minimizing-isolate-catalyst-motion-in-metal-assisted-chemical-etching-for-deep-trenching-of-silicon-nanohole-array
#12
Lingyu Kong, Yunshan Zhao, Binayak Dasgupta, Yi Ren, Kedar Hippalgaonkar, Xiuling Li, Wai Kin Chim, Sing Yang Chiam
The instability of isolate catalysts during metal-assisted chemical etching is a major hindrance to achieve high aspect ratio structures in the vertical and directional etching of silicon (Si). In this work, we discussed and showed how isolate catalyst motion can be influenced and controlled by the semiconductor doping type and the oxidant concentration ratio. We propose that the triggering event in deviating isolate catalyst motion is brought about by unequal etch rates across the isolate catalyst. This triggering event is indirectly affected by the oxidant concentration ratio through the etching rates...
May 23, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28534609/au-promoted-nickel-iron-layered-double-hydroxide-nanoarrays-a-modular-catalyst-enabling-high-performance-oxygen-evolution
#13
Wenxin Zhu, Lizhi Liu, Zhihao Yue, Wentao Zhang, Xiaoyue Yue, Jing Wang, Shaoxuan Yu, Li Wang, Jianlong Wang
Oxygen evolution reaction (OER) has played a pivotal role in many energy conversion and storage technologies like water electrolysis, fuel cells, and metal-air batteries. However, the slow kinetics of OER limit the performance and commercialization of such devices. Herein, we report on NiFe LDH@Au hybrid nanoarrays on Ni foam for much enhanced OER. By hybridization of electronegative Au and NiFe LDH with intrinsic remarkable OER catalytic activity, this modular electrode could drive an overall ultrahigh-performance and robust OER in base with the demand of overpotentials of only 221, 235 and 270 mV to afford 50, 100 and 500 mA cm-2, respectively...
May 23, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28534593/molecular-catalysts-for-artificial-photosynthesis-general-discussion
#14
Mei Wang, Vincent Artero, Leif Hammarström, Jose Martinez, Joshua Karlsson, Devens Gust, Peter Summers, Charles Machan, Peter Brueggeller, Christopher D Windle, Yosuke Kageshima, Richard Cogdell, Kristine Rodulfo Tolod, Alexander Kibler, Dogukan Hazar Apaydin, Etsuko Fujita, Johannes Ehrmaier, Seigo Shima, Elizabeth Gibson, Ferdi Karadas, Anthony Harriman, Haruo Inoue, Akihiko Kudo, Tomoaki Takayama, Michael Wasielewski, Flavia Cassiola, Masayuki Yagi, Hitoshi Ishida, Federico Franco, Sang Ook Kang, Daniel Nocera, Can Li, Fabio Di Fonzo, Hyunwoong Park, Licheng Sun, Tohru Setoyama, Young Soo Kang, Osamu Ishitani, Jian-Ren Shen, Ho-Jin Son, Shigeyuki Masaoka
No abstract text is available yet for this article.
May 23, 2017: Faraday Discussions
https://www.readbyqxmd.com/read/28534582/selective-conversion-of-coconut-oil-to-fatty-alcohols-in-methanol-over-a-hydrothermally-prepared-cu-sio2-catalyst-without-extraneous-hydrogen
#15
Liubi Wu, Lulu Li, Bolong Li, Chen Zhao
A novel one-pot approach selects a hydrothermally synthesized Cu/SiO2 catalyst (consisting of Cu2O·SiO2 and Cu(0) surface species) to catalyze the reduction of a series of fatty esters, fatty acids, and coconut oil to fatty alcohols at 240 °C in methanol without extraneous hydrogen, attaining around 85% conversion and 100% selectivity.
May 23, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28534563/enhanced-catalytic-performance-of-a-pdo-catalyst-prepared-via-a-two-step-method-of-in-situ-reduction-oxidation
#16
Wei Hu, Guang-Xia Li, Jian-Jun Chen, Fu-Jin Huang, Yang Wu, Shan-Dong Yuan, Lin Zhong, Yao-Qiang Chen
A supported PdO nanocatalyst prepared by a facile in situ reduction process followed by an oxidation step showed significantly enhanced activity for the removal of pollutants from natural gas vehicles. The excellent catalytic performance is mainly due to high dispersion of the uniform PdO nanoparticles generated during the novel two-step method.
May 23, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28534207/construction-of-polyarylenes-with-various-structural-features-via-bergman-cyclization-polymerization
#17
REVIEW
Youfu Wang, Shudan Chen, Aiguo Hu
Synthetic polymer chemistry is a fundamental part of polymer science, and highly efficient polymerization reactions are essential for the synthesis of high-performance polymers. Development of new synthetic methods for emerging polymer science is of great importance in this regard. Bergman cyclization is a chemical process in which highly reactive aryl diradicals form from enediyne precursors, having a strong impact in a number of fields including pharmaceutics, synthetic chemistry, and materials science. Diradical intermediates stemming from enediynes can cause DNA cleavage under physiological conditions, leading to the strong cytotoxicity of many naturally occurring enediyne antibiotics...
June 2017: Topics in Current Chemistry (Journal)
https://www.readbyqxmd.com/read/28533833/application-of-the-socio-ecological-model-to-predict-physical-activity-behaviour-among-nigerian-university-students
#18
Inimfon Aniema Essiet, Anisah Baharom, Hayati Kadir Shahar, Benjamin Uzochukwu
INTRODUCTION: Physical activity among university students is a catalyst for habitual physical activity in adulthood. Physical activity has many health benefits besides the improvement in academic performance. The present study assessed the predictors of physical activity among Nigerian university students using the Social Ecological Model (SEM). METHODS: This cross-sectional study recruited first-year undergraduate students in the University of Uyo, Nigeria by multistage sampling...
2017: Pan African Medical Journal
https://www.readbyqxmd.com/read/28533451/animal-coloration-research-why-it-matters
#19
Tim Caro, Mary Caswell Stoddard, Devi Stuart-Fox
While basic research on animal coloration is the theme of this special edition, here we highlight its applied significance for industry, innovation and society. Both the nanophotonic structures producing stunning optical effects and the colour perception mechanisms in animals are extremely diverse, having been honed over millions of years of evolution for many different purposes. Consequently, there is a wealth of opportunity for biomimetic and bioinspired applications of animal coloration research, spanning colour production, perception and function...
July 5, 2017: Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences
https://www.readbyqxmd.com/read/28533413/confined-catalysis-under-two-dimensional-materials
#20
Haobo Li, Jianping Xiao, Qiang Fu, Xinhe Bao
Confined microenvironments formed in heterogeneous catalysts have recently been recognized as equally important as catalytically active sites. Understanding the fundamentals of confined catalysis has become an important topic in heterogeneous catalysis. Well-defined 2D space between a catalyst surface and a 2D material overlayer provides an ideal microenvironment to explore the confined catalysis experimentally and theoretically. Using density functional theory calculations, we reveal that adsorption of atoms and molecules on a Pt(111) surface always has been weakened under monolayer graphene, which is attributed to the geometric constraint and confinement field in the 2D space between the graphene overlayer and the Pt(111) surface...
May 22, 2017: Proceedings of the National Academy of Sciences of the United States of America
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