共查询到20条相似文献,搜索用时 31 毫秒
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Alena Rudolph Mark Lautens Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(15):2656-2670
Secondary, but second to none : The use of secondary alkyl halides in transition‐metal‐catalyzed cross‐coupling reactions (see scheme) has advanced significantly over the last five years. Selected examples of these transformations are examined, including mechanistic and stereochemical aspects.
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Peter G. Jones Lilian Gray 《Acta Crystallographica. Section C, Structural Chemistry》2002,58(5):o282-o283
The crystal packing of the title compound, C8H11BrN+·Br?, involves three types of secondary interaction: a classical N—H?Br? hydrogen bond, a `weak' but short C—H?Br? interaction (normalized H?Br distance of 2.66 Å) and a cation–anion Br?Br contact of 3.6331 (4) Å. The hydrogen bonds connect two cations and two anions to form rings of graph set R(14). The Br?Br contacts link these rings to form layers parallel to the bc plane. 相似文献
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Klaus Merz 《Acta Crystallographica. Section C, Structural Chemistry》2003,59(2):o65-o67
The crystal packing of 1‐iodo‐3‐nitrobenzene, C6H4INO2, is formed by planar molecules which are linked by I⋯I and NO2⋯NO2 interactions. In the case of 1‐iodo‐3,5‐dinitrobenzene, C6H3IN2O4, the NO2 groups are not exactly coplanar with the benzene ring and the molecules form sheets linked by NO2⋯NO2 interactions. In contrast with 4‐iodonitrobenzene, the crystal structures of both title compounds do not form highly symmetrical I⋯NO2 intermolecular interactions. 相似文献
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Chen‐Ming Lin Maritess Arancillo Jonathan Whisenant Kevin Burgess 《Angewandte Chemie (International ed. in English)》2020,59(24):9398-9402
Secondary structures tend to be recognizable because they have repeating structural motifs, but mimicry of these does not have to follow such well‐defined patterns. Bioinformatics studies to match side‐chain orientations of a novel hydantoin triazole chemotype ( 1 ) to protein‐protein interfaces revealed it tends to align well across parallel and antiparallel sheets, like rungs on a ladder. One set of these overlays was observed for the protein‐protein interaction uPA?uPAR. Consequently, chemotype 1 was made with appropriate side‐chains to mimic uPA at this interface. Biophysical assays indicate these compounds did in fact bind uPAR, and elicit cellular responses that affected invasion, migration, and wound healing. 相似文献
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Dr. Wei Ou Feng Han Xiu‐Ning Hu Hang Chen Prof. Dr. Pei‐Qiang Huang 《Angewandte Chemie (International ed. in English)》2018,57(35):11354-11358
Reported herein is the first direct, metal‐catalyzed reductive functionalization of secondary amides to give functionalized amines and heterocycles. The method is shown to have exceptionally broad scope with respect to suitable nucleophiles, which cover both hard and soft C nucleophiles as well as a P nucleophile. The reaction exhibits good chemoselectivity and tolerates several sensitive functional groups. 相似文献
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The (2E,4E)‐ and (2E,4Z)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene reacts with aziridine to give aziridinecyclopentenol 3. This product arises from an intermolecular Michael addition of a nitrogen lone pair to the less reactive enone, followed by an intramolecular aldol reaction of the enol with ketone. Furthermore, the initially formed enol did not undergo nucleophilic attack onto the aziridine ring to form heterocycles. Interestingly, the reaction with secondary amine did not give the cyclopentenol adduct, and this only leads to the isomerization of (2E,4Z)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene to the more stable (2E,4E)‐1‐phenyl‐1,6‐dioxo‐hepta‐2,4‐diene by addition to the more reactive enone. 相似文献
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Hai‐tao Zhang Prof. Dr. Xiao‐dong Fan Prof. Dr. Wei Tian Rong‐tian Suo Zhen Yang Yang Bai Wan‐bin Zhang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(13):5000-5008
The controlled secondary self‐assembly of amphiphilic molecules in solution is theoretically and practically significant in amphiphilic molecular applications. An amphiphilic β‐cyclodextrin (β‐CD) dimer, namely LA‐(CD)2, has been synthesized, wherein one lithocholic acid (LA) unit is hydrophobic and two β‐CD units are hydrophilic. In an aqueous solution at room temperature, LA‐(CD)2 self‐assembles into spherical micelles without ultrasonication. The primary micelles dissociates and then secondarily form self‐assemblies with branched structures under ultrasonication. The branched aggregates revert to primary micelles at high temperature. The ultrasound‐driven secondary self‐assembly is confirmed by transmission electron microscopy, dynamic light scattering, 1H NMR spectroscopy, and Cu2+‐responsive experiments. Furthermore, 2D NOESY NMR and UV/Vis spectroscopy results indicate that the formation of the primary micelles is driven by hydrophilic–hydrophobic interactions, whereas host–guest interactions promote the formation of the secondary assemblies. Additionally, ultrasonication is shown to be able to effectively destroy the primary hydrophilic–hydrophobic balances while enhancing the host–guest interaction between the LA and β‐CD moieties at room temperature. 相似文献
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Dr. Stepan Shipovskov Prof. Cristiano L. P. Oliveira Søren Vrønning Hoffmann Dr. Leif Schauser Prof. Duncan S. Sutherland Prof. Flemming Besenbacher Prof. Jan Skov Pedersen 《Chemphyschem》2012,13(13):3179-3184
A scheme is presented in which an organic solvent environment in combination with surfactants is used to confine a natively unfolded protein inside an inverse microemulsion droplet. This type of confinement allows a study that provides unique insight into the dynamic structure of an unfolded, flexible protein which is still solvated and thus under near‐physiological conditions. In a model system, the protein osteopontin (OPN) is used. It is a highly phosphorylated glycoprotein that is expressed in a wide range of cells and tissues for which limited structural analysis exists due to the high degree of flexibility and large number of post‐translational modifications. OPN is implicated in tissue functions, such as inflammation and mineralisation. It also has a key function in tumour metastasis and progression. Circular dichroism measurements show that confinement enhances the secondary structural features of the protein. Small‐angle X‐ray scattering and dynamic light scattering show that OPN changes from being a flexible protein in aqueous solution to adopting a less flexible and more compact structure inside the microemulsion droplets. This novel approach for confining proteins while they are still hydrated may aid in studying the structure of a wide range of natively unfolded proteins. 相似文献
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The Selective Cross‐Coupling of Secondary Alkyl Zinc Reagents to Five‐Membered‐Ring Heterocycles Using Pd‐PEPPSI‐IHeptCl 下载免费PDF全文
Dr. Bruce Atwater Dr. Nalin Chandrasoma Dr. David Mitchell Dr. Michael J. Rodriguez Matthew Pompeo Dr. Robert D. J. Froese Prof. Michael G. Organ 《Angewandte Chemie (International ed. in English)》2015,54(33):9502-9506
The ability to cross‐couple secondary alkyl centers is fraught with a number of problems, including difficult reductive elimination, which often leads to β‐hydride elimination. Whereas catalysts have been reported that provide decent selectivity for the expected (non‐rearranged) cross‐coupled product with aryl or heteroaryl oxidative‐addition partners, none have shown reliable selectivity with five‐membered‐ring heterocycles. In this report, a new, rationally designed catalyst, Pd‐PEPPSI‐IHeptCl, is demonstrated to be effective in selective cross‐coupling reactions with secondary alkyl reagents across an impressive variety of furans, thiophenes, and benzo‐fused derivatives (e.g., indoles, benzofurans), in most instances producing clean products with minimal, if any, migratory insertion for the first time. 相似文献
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Xiaowei Jiang Yao Wang Wangqing Zhang Peiwen Zheng Linqi Shi 《Macromolecular rapid communications》2006,27(21):1833-1837
Summary: Raspberry‐like aggregates containing secondary nanospheres were studied. The formation of raspberry‐like aggregates was due to complexation between core‐shell microspheres and core‐corona micelles. The core‐shell microspheres were synthesized with soap‐free polymerization of styrene and methyl acrylic acid, which included carboxyl groups in the periphery. The micelles were self‐assembled by polystyrene‐block‐poly(4‐vinylpyridine), which contained pyridine groups in the corona. The driven force to form raspberry‐like aggregates was due to the affinity between the carboxyl and pyridine groups. The morphology of the raspberry‐like aggregates could be tuned by changing the ratio of the microspheres to micelles. IR measurements suggested that the raspberry‐like aggregates were like zwitterions.
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Recently, we developed methods to stabilize peptides into various secondary structures, including α‐helix, type III turn and β‐hairpin via proper thioether based macrocyclization. These conformationally constrained peptidomimetics confer enhanced biophysical properties and provide a valuable avenue towards clinically‐relevant therapeutic molecules. In this personal account, thioether‐derived macrocyclization methods developed by our group for stabilization of α‐helix, type‐III β turn and β‐hairpin conformations are discussed. 相似文献
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Jeffrey N. McKnight Eric S. Tillman Louis R. Sarry 《Macromolecular rapid communications》2006,27(18):1578-1583
Summary: The cationic polymerization of poly(tert‐butyl vinyl ether) using N‐methyleneamine equivalents derived from a Lewis acid/1,3,5‐trimethylhexahydro‐1,3,5‐triazine (TMTA) co‐initiating system is reported. The resulting polymers possessed secondary amine functionality at the chain terminus, verified by derivatization with 4‐chloro‐7‐nitrobenzo‐2‐oxa‐1,3‐diazole (NBD‐Cl) and subsequent analysis with GPC‐UV (470 nm) and 1H NMR.
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Copper‐Catalyzed γ‐Selective and Stereospecific Allylic Cross‐Coupling with Secondary Alkylboranes 下载免费PDF全文
Yuto Yasuda Kazunori Nagao Yoshinori Shido Prof. Dr. Seiji Mori Prof. Dr. Hirohisa Ohmiya Prof. Dr. Masaya Sawamura 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(27):9666-9670
The scope of the copper‐catalyzed coupling reactions between organoboron compounds and allylic phosphates is expanded significantly by employing triphenylphosphine as a ligand for copper, allowing the use of secondary alkylboron compounds. The reaction proceeds with complete γ‐E‐selectivity and preferential 1,3‐syn stereoselectivity. The reaction of γ‐silicon‐substituted allylic phosphates affords enantioenriched α‐stereogenic allylsilanes. 相似文献
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Ethan A. Wappes Stacy C. Fosu Trevor C. Chopko Prof. Dr. David A. Nagib 《Angewandte Chemie (International ed. in English)》2016,55(34):9974-9978
The Cδ?H amination of unactivated, secondary C?H bonds to form a broad range of functionalized pyrrolidines has been developed by a triiodide (I3?)‐mediated strategy. By in situ 1) oxidation of sodium iodide and 2) sequestration of the transiently generated iodine (I2) as I3?, this approach precludes undesired I2‐mediated decomposition which can otherwise limit synthetic utility to only weak C(sp3)?H bonds. The mechanism of this triiodide‐mediated cyclization of unbiased, secondary C(sp3)?H bonds, by either thermal or photolytic initiation, is supported by NMR and UV/Vis data, as well as intercepted intermediates. 相似文献