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Gold catalysis

Rachelle Quach, Daniel P Furkert, Margaret A Brimble
In the last decade the use of homogenous gold catalysts has rapidly grown and become a valuable tool for complex natural product synthesis. Spiroketal natural products are valuable targets for total synthesis and medicinal chemistry applications. The use of gold catalysts has emerged as a useful tool to synthesise these privileged scaffolds. This review summarises the application of gold catalysis for the syntheses of spiro, bridged and fused ketal natural products.
March 13, 2017: Organic & Biomolecular Chemistry
Chenyang Sun, Xiao Yuan, Yan Li, Xiaoxiao Li, Zhigang Zhao
A N(1)-selective alkenylation of 1-sulfonyl-1,2,3-triazoles with alkynes via gold catalysis is reported. N(1)-Vinyl substituted 1,2,3-triazoles were selectively prepared in up to 92% yield through the sulfonyl group of 1,2,3-triazole derivatives transformed to alkenyl groups in a "one-pot two steps" manner. This method provided a new method for the synthesis of potentially biological-active vinyl-triazole building blocks.
March 10, 2017: Organic & Biomolecular Chemistry
Kyuju Kwak, Woojun Choi, Qing Tang, Minseok Kim, Yongjin Lee, De-En Jiang, Dongil Lee
The theoretically predicted volcano plot for hydrogen production shows the best catalyst as the one that ensures that the hydrogen binding step is thermodynamically neutral. However, the experimental realization of this concept has suffered from the inherent surface heterogeneity of solid catalysts. It is even more challenging for molecular catalysts because of their complex chemical environment. Here, we report that the thermoneutral catalyst can be prepared by simple doping of a platinum atom into a molecule-like gold nanocluster...
March 10, 2017: Nature Communications
Subin Choi, Vunnam Srinivasulu, Sujin Ha, Cheol-Min Park
An efficient synthetic method for carbazoles has been developed employing diazo anilinoalkynes as substrates. Sequential activation of the orthogonal functional groups embedded in diazo anilinoalkyne substrates by tandem gold-copper catalysis leads to the formation of highly substituted carbazoles. Substrate scope reveals a broad tolerability toward the substitution on aryl groups.
March 9, 2017: Chemical Communications: Chem Comm
Romain Poupart, Antoine Benlahoues, Benjamin Le Droumaguet, Daniel Grande
Original nanoporous catalytic supports can be engineered via an effective and straightforward synthetic route to polystyrene-block-poly(D,L-lactide) diblock copolymer precursors displaying an acid-cleavable acetal junction between both blocks. To this purpose, an acetal-containing hetero-difunctional initiator was synthesized, thus enabling to combine two different polymerization methods, i.e. first Atom Transfer Radical Polymerization (ATRP) of styrene, and then Ring-Opening Polymerization (ROP) of D,L-lactide...
March 7, 2017: ACS Applied Materials & Interfaces
Debdip Bhandary, Vasumathi Valechi, Maria Natália D S Cordeiro, Jayant K Singh
Janus particles provide an asymmetry in structure, which can impart diverse functionalities leading to immense importance in various applications, ranging from targeted delivery to interfacial phenomena, including catalysis, electronics, and optics. In this work, we present results of a molecular dynamics study of the growth mechanism of coating on gold nanoparticles (AuNPs) from droplets of n-alkyl thiols with different chain lengths (C5 and C11) and terminal groups (CH3 and COOH). The effect of chain lengths and functional groups on the formation of a monolayer of alkyl thiols on AuNPs is investigated...
March 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Ghibom Bhak, Junghee Lee, Chang-Hyun Kim, Dong Young Chung, Jin Hyoun Kang, Soojung Oh, Jungsup Lee, Jin Soo Kang, Ji Mun Yoo, Jee Eun Yang, Kun Yil Rhoo, Sunghak Park, Somin Lee, Ki Tae Nam, Noo Li Jeon, Jyongsik Jang, Byung Hee Hong, Yung-Eun Sung, Myung-Han Yoon, Seung R Paik
Functional graffiti of nanoparticles onto target surface is an important issue in the development of nanodevices. A general strategy has been introduced here to decorate chemically diverse substrates with gold nanoparticles (AuNPs) in the form of a close-packed single layer by using an omni-adhesive protein of α-synuclein (αS) as conjugated with the particles. Since the adsorption was highly sensitive to pH, the amino acid sequence of αS exposed from the conjugates and its conformationally disordered state capable of exhibiting structural plasticity are considered to be responsible for the single-layer coating over diverse surfaces...
March 1, 2017: ACS Applied Materials & Interfaces
Zhengnan Shen, Hani Mobarak, Wei Li, Göran Widmalm, Biao Yu
The β-(1→2)-linked 6-deoxy-l-altropyranose di- to pentasaccharides 2-5, relevant to the O-antigen of the infectious Yersinia enterocolitica O:3, were synthesized for the first time. The challenging 1,2-cis-altropyranosyl linkage was assembled effectively via glycosylation with 2-O-benzyl-3,4-di-O-benzoyl-6-deoxy-l-altropyranosyl ortho-hexynylbenzoate (7) under the catalysis of PPh3AuNTf2. NMR and molecular modeling studies showed that the pentasaccharide (5) adopted a left-handed helical conformation.
March 2, 2017: Journal of Organic Chemistry
Kasper P Kepp
Gold plays a major role in nanochemistry, catalysis, and electrochemistry. Accordingly, hundreds of studies apply density functionals to study chemical bonding with gold, yet there is no systematic attempt to assess the accuracy of these methods applied to gold. This paper reports a benchmark against 51 experimental bond enthalpies of AuX systems and seven additional polyatomic and cationic molecules. Twelve density functionals were tested, covering meta functionals, hybrids with variable HF exchange, double-hybrid, dispersion-corrected, and nonhybrid GGA functionals...
February 24, 2017: Journal of Physical Chemistry. A
Kazuki Tsubokura, Kenward K H Vong, Ambara R Pradipta, Akihiro Ogura, Sayaka Urano, Tsuyoshi Tahara, Satoshi Nozaki, Hirotaka Onoe, Yoichi Nakao, Regina Sibgatullina, Almira Kurbangalieva, Yasuyoshi Watanabe, Katsunori Tanaka
Metal complex catalysis within biological systems is largely limited to cell and bacterial systems. In this work, a glycoalbumin-Au(III) complex was designed and developed that enables organ-specific, localized propargyl ester amidation with nearby proteins within live mice. The targeted reactivity can be imaged through the use of Cy7.5- and TAMRA-linked propargyl ester based fluorescent probes. This targeting system could enable the exploitation of other metal catalysis strategies for biomedical and clinical applications...
February 15, 2017: Angewandte Chemie
Yen-Chun Lee, Sumersing Patil, Christopher Golz, Carsten Strohmann, Slava Ziegler, Kamal Kumar, Herbert Waldmann
The selective transformation of different starting materials by different metal catalysts under individually optimized reaction conditions to structurally different intermediates and products is a powerful approach to generate diverse molecular scaffolds. In a more unified albeit synthetically challenging strategy, common starting materials would be exposed to a common metal catalysis, leading to a common intermediate and giving rise to different scaffolds by tuning the reactivity of the metal catalyst through different ligands...
February 14, 2017: Nature Communications
John R Finnegan, Jessica Gwyther, Ian Manners
Patch works! Patchy block copolymer micelles with a corona consisting of two chemically different patches have been designed for the selective binding of catalytically active nanoparticles. The fabrication of nonwoven supports by electrospinning was combined with crystallization-driven self-assembly for precise control over micelle formation to prepare a new recyclable catalyst platform.
February 10, 2017: Angewandte Chemie
Daksh Agarwal, Carlos O Aspetti, Matteo Cargnello, MingLiang Ren, Jinkyoung Yoo, Christopher B Murray, Ritesh Agarwal
The field of plasmonics has attracted considerable attention in recent years because of potential applications in various fields such as nanophotonics, photovoltaics, energy conversion, catalysis, and therapeutics. It is becoming increasing clear that intrinsic high losses associated with plasmons can be utilized to create new device concepts to harvest the generated heat. It is therefore important to design cavities, which can harvest optical excitations efficiently to generate heat. We report a highly engineered nanowire cavity, which utilizes a high dielectric silicon core with a thin plasmonic film (Au) to create an effective metallic cavity to strongly confine light, which when coupled with localized surface plasmons in the nanoparticles of the thin metal film produces exceptionally high temperatures upon laser irradiation...
March 8, 2017: Nano Letters
Jian-Fang Cui, Hok-Ming Ko, Ka-Pan Shing, Jie-Ren Deng, Nathanael Chun-Him Lai, Man-Kin Wong
Unprecedented stable BINOL/gold(III) complexes, adopting a novel C,O-chelation mode, were synthesized by a modular approach through combination of 1,1'-binaphthalene-2,2'-diols (BINOLs) and cyclometalated gold(III) dichloride complexes [(C^N)AuCl2 ]. X-ray crystallographic analysis revealed that the bidentate BINOL ligands tautomerized and bonded to the Au(III) atom through C,O-chelation to form a five-membered ring instead of the conventional O,O'-chelation giving a seven-membered ring. These gold(III) complexes catalyzed acetalization/cycloisomerization and carboalkoxylation of ortho-alkynylbenzaldehydes with trialkyl orthoformates...
February 6, 2017: Angewandte Chemie
Khwaja Salahuddin Siddiqi, Azamal Husen
For biosynthesis of gold nanoparticles different parts of a plant are used as they contain metabolites such as alkaloids, flavonoids, phenols, terpenoids, alcohols, sugars and proteins which act as reducing agents to produce nanoparticles. They also act as capping agent and stabilizer for them. They are used in medicine, agriculture and many other technologies. The attention is therefore focussed on all plant species which have either aroma or colour in their leaves, flowers or roots for the synthesis of nanoparticles because they all contain such chemicals which reduce the metal ions to metal nanoparticles...
March 2017: Journal of Trace Elements in Medicine and Biology
Pei Zuo, Lan Jiang, Xin Li, Bo Li, Yongda Xu, Xuesong Shi, Peng Ran, Tianbao Ma, Dawei Li, Liangti Qu, Yongfeng Lu, Costas P Grigoropoulos
Edge-active site control of MoS2 is crucial for applications such as chemical catalysis, synthesis of functional composites, and biochemical sensing. This work presents a novel nonthermal method to simultaneously tune surface chemical (edge-active sites) and physical (surface periodic micro/nano structures) properties of MoS2 using temporally shaped femtosecond pulses, through which shape-controlled gold nanoparticles are in situ and self-assembly grown on MoS2 surfaces to form Au-MoS2 hybrids. The edge-active sites with unbound sulfurs of laser-treated MoS2 drive the reduction of gold nanoparticles, while the surface periodic structures of laser-treated MoS2 assist the shape-controllable growth of gold nanoparticles...
March 1, 2017: ACS Applied Materials & Interfaces
Simona Neri, Sergio Garcia Martin, Cristian Pezzato, Leonard J Prins
The activity of a gold nanoparticle-based catalyst can be reversibly up- and down-regulated by light. Light is used to switch a small molecule between cis- and trans-isomers, which inhibits the catalytic activity of the nanoparticles to different extent. The system is functional in aqueous buffer, which paves the way for integrating the system in biological networks.
January 26, 2017: Journal of the American Chemical Society
Fu-Min Liao, Zhong-Yan Cao, Jin-Sheng Yu, Jian Zhou
We report a highly stereoselective synthesis of all-carbon or fluorinated tetrasubstituted alkenes from diazo reagents and fluorinated enol silyl ethers, using C-F bond as a synthetic handle. Cationic Au(I) catalysis plays a key role in this reaction. Remarkable fluorine effects on the reactivity and selectivity was also observed.
January 18, 2017: Angewandte Chemie
Courtney A Smith, Stephen E Motika, Lukasz Wojtas, Xiaodong Shi
An intermolecular condensation of alkynols and terminal alkynes is reported. Using IPrAuNTf2, an efficient Au-catalyzed cyclization-alkynylation strategy furnishes (2-arylalkynyl) cyclic ethers in moderate to excellent yields (up to 94%). This strategy is extended to the synthesis of functionalized 2,3-dihydrooxepines via the sequential Au-catalyzed ring expansion of the cyclic ether substrates.
February 16, 2017: Chemical Communications: Chem Comm
Kang Liu, Yanru Bu, Yuanhui Zheng, Xuchuan Jiang, Aibing Yu, Huanting Wang
Gold nanorods (AuNRs) are versatile materials due to their broadly tunable optical properties associated with their anisotropic feature. Conventional seed-mediated synthesis is, however, not only limited by the operational complexity and over-sensitivity towards subtle changes of experimental conditions but also suffers from low yield (≈15 %). A facile seedless method is reported to overcome these challenges. Monodispersed AuNRs with high yield (≈100 %) and highly adjustable longitudinal surface plasmon resonance (LSPR) are reproducibly synthesized...
January 10, 2017: Chemistry: a European Journal
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