共查询到20条相似文献,搜索用时 15 毫秒
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Dr. Nguyet Trang Thanh Chau Maxime Meyer Dr. Shinsuke Komagawa Dr. Floris Chevallier Prof. Yves Fort Prof. Masanobu Uchiyama Prof. Florence Mongin Dr. Philippe C. Gros 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(41):12425-12433
Homoleptic lithium tri‐ and tetraalkyl zincates were reacted with a set of bromopyridines. Efficient and chemoselective bromine–metal exchanges were realized at room temperature with a substoichiometric amount of nBu4ZnLi2?TMEDA reagent (1/3 equiv; TMEDA=N,N,N′,N′‐tetramethylethylenediamine). This reactivity contrasted with that of tBu4ZnLi2?TMEDA, which was inefficient below one equivalent. DFT calculations allowed us to rationalize the formation of N???Li stabilized polypyridyl zincates in the reaction. The one‐pot difunctionalization of dibromopyridines was also realized using the reagent stoichiometrically. The direct creation of C? Zn bonds in bromopyridines enabled us to perform efficient Negishi‐type cross‐couplings. 相似文献
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Lucile Anthore‐Dalion Andreas D. Benischke Baosheng Wei Guillaume Berionni Paul Knochel 《Angewandte Chemie (International ed. in English)》2019,58(12):4046-4050
Fast I/Sm and Br/Sm exchanges take place when various aromatic or heterocyclic iodides and bromides are treated with nBu2SmCl?4 LiCl and nBu3Sm?5 LiCl, respectively. The resulting organosamarium reagents were efficiently quenched with aldehydes, ketones, and imines. Also, they undergo acylations when treated with N,N‐dimethylamides leading to ketones. The rate of the Br/Sm exchange for a typical aryl bromide was determined and found to be 8.5×105 faster than the Br/Mg exchange, indicating that the rate of a metal‐exchange is related to the ionic character of the carbon–metal bond and to the metal electronegativity. 相似文献
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Shinji Nakamura Dr. Ching‐Yuan Liu Dr. Atsuya Muranaka Dr. Masanobu Uchiyama Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(23):5686-5694
Zincate it! The mechanism of the halogen–zinc exchange reaction with organozincate compounds has been studied by using density functional theory to elucidate the effects of changing the halogen species, the alkyl ligand on zinc, and the substrate nature (see figure).
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Laure Boymond Mario Rottlnder Grard Cahiez Paul Knochel 《Angewandte Chemie (International ed. in English)》1998,37(12):1701-1703
At −40°C aryl iodides that contain other functional groups can be selectively converted into Grignard reagents, which react with electrophiles such as benzaldehyde in the usual manner [Eq. (a)]. Aryl bromides and iodides that are immobilized as esters on a Wang resin behave analogously. 相似文献
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Baosheng Wei Dongchao Zhang Yi‐Hung Chen Aiwen Lei Paul Knochel 《Angewandte Chemie (International ed. in English)》2019,58(44):15631-15635
Various aryl‐ and heteroaryl‐substituted 2‐bromobiaryls are converted to cyclometalated lanthanum intermediates by reaction with nBu2LaCl?4 LiCl. These resulting lanthanum heterocycles are key intermediates for the facile preparation of functionalized 2,2′‐diiodobiaryls, silafluorenes, fluoren‐9‐ones, phenanthrenes, and their related heterocyclic analogues. X‐ray absorption fine structure (XAFS) spectroscopy was used to rationalize the proposed structures of the involved organolanthanum species. 相似文献
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Generation of Aryl and Heteroaryl Magnesium Reagents in Toluene by Br/Mg or Cl/Mg Exchange 下载免费PDF全文
Dorothée S. Ziegler Prof. Dr. Konstantin Karaghiosoff Prof. Dr. Paul Knochel 《Angewandte Chemie (International ed. in English)》2018,57(22):6701-6704
The alkylmagnesium alkoxide sBuMgOR?LiOR (R=2‐ethylhexyl), which was prepared as a 1.5 m solution in toluene, undergoes very fast Br/Mg exchange with aryl and heteroaryl bromides, producing aryl and heteroaryl magnesium alkoxides (ArMgOR?LiOR) in toluene. These Grignard reagents react with a broad range of electrophiles, including aldehydes, ketones, allyl bromides, acyl chlorides, epoxides, and aziridines, in good yields. Remarkably, the related reagent sBu2Mg?2 LiOR (R=2‐ethylhexyl) undergoes Cl/Mg exchange with various electron‐rich aryl chlorides in toluene, producing diorganomagnesium species of type Ar2Mg?2 LiOR, which react well with aldehydes and allyl bromides. 相似文献
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Shinji Nakamura Dr. Ching‐Yuan Liu Dr. Atsuya Muranaka Dr. Masanobu Uchiyama Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(23):5619-5619
Density functional theory and fragment‐energy analysis have been used to probe the mechanism of the halogen–zinc exchange reaction. In their Full Paper on page 5686 ff. , M. Uchiyama, S. Nakamura et al. discuss three important factors in this reaction: The effect of the halogen species, the effect of the alkyl ligand on zinc, and the effect of the substrate nature.
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Christina Heroven Victoria Georgi Gaurav K. Ganotra Prof. Paul Brennan Finn Wolfreys Prof. Dr. Rebecca C. Wade Amaury E. Fernández‐Montalván Apirat Chaikuad Prof. Dr. Stefan Knapp 《Angewandte Chemie (International ed. in English)》2018,57(24):7220-7224
Prolonged drug residence times may result in longer‐lasting drug efficacy, improved pharmacodynamic properties, and “kinetic selectivity” over off‐targets with high drug dissociation rates. However, few strategies have been elaborated to rationally modulate drug residence time and thereby to integrate this key property into the drug development process. Herein, we show that the interaction between a halogen moiety on an inhibitor and an aromatic residue in the target protein can significantly increase inhibitor residence time. By using the interaction of the serine/threonine kinase haspin with 5‐iodotubercidin (5‐iTU) derivatives as a model for an archetypal active‐state (type I) kinase–inhibitor binding mode, we demonstrate that inhibitor residence times markedly increase with the size and polarizability of the halogen atom. The halogen–aromatic π interactions in the haspin–inhibitor complexes were characterized by means of kinetic, thermodynamic, and structural measurements along with binding‐energy calculations. 相似文献
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《Angewandte Chemie (International ed. in English)》2017,56(41):12770-12773
We report a halogen–lithium exchange performed in the presence of various metal salts (ZnCl2, MgCl2⋅LiCl) on a broad range of sensitive bromo‐ or iodo(hetero)arenes using BuLi or PhLi as the exchange reagent and a commercially available continuous‐flow setup. The resulting diarylmagnesium or diarylzinc species were trapped with various electrophiles, resulting in the formation of polyfunctional (hetero)arenes in high yields. This method enables the functionalization of (hetero)arenes containing highly sensitive groups such as an isothiocyanate, nitro, azide, or ester. A straightforward scale‐up was possible without further optimization. 相似文献
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Metal‐Ion Metathesis and Properties of Triarylboron‐Functionalized Metal–Organic Frameworks 下载免费PDF全文
Xiaoqing Wang Liangliang Zhang Jie Yang Fangna Dai Prof. Rongming Wang Prof. Daofeng Sun 《化学:亚洲杂志》2015,10(7):1535-1540
An anionic metal–organic framework, H3[(Mn4Cl)3 L 8]?30 H2O?2.5 DMF?5 Diox ( UPC‐15 ), was successfully prepared by the reaction of MnCl2 with tris(p‐carboxylic acid)tridurylborane (H3 L ) under solvothermal conditions. UPC‐15 with wide‐open pores (~18.8 Å) is constructed by packing of octahedral and cuboctahedral cages, and exhibits high gas‐sorption capabilities. Notably, UPC‐15 shows selective adsorption of cationic dyes due to the anion framework. Moreover, the catalytic and magnetic properties were investigated, and UPC‐15 can highly catalyze the cyanosilylation of aromatic aldehydes. UPC‐15 exhibits the exchange of metal ions from Mn to Cu in a single‐crystal‐to‐single‐crystal manner to generate UPC‐16 , which could not be obtained by the direct solvothermal reaction of CuCl2 and H3 L. UPC‐16 exhibits similar properties for gas sorption, dye separation, and catalytic activity. However, the magnetic behaviors for UPC‐15 and UPC‐16 are distinct due to the metal‐specific properties. Below 47 K, UPC‐15 exhibits a ferromagnetic coupling but UPC‐16 shows a dominant antiferromagnetic behavior. 相似文献
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Matthias Franke Florencia Marchini Prof. Dr. Norbert Jux Prof. Dr. Hans‐Peter Steinrück Dr. Ole Lytken Prof. Dr. Federico J. Williams 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(25):8520-8524
Demetalation of zinc 5,10,15,20‐tetraphenylporphyrin (ZnTPP) under acidic conditions and ion exchange with Cu2+ ions at neutral pH are both rapid reactions in the liquid medium. However, for ZnTPP monolayers adsorbed on a Au(111) surface exposed to aqueous solution, we find that, although ion exchange takes place rapidly as expected, demetalation does not occur, even at pH values as low as 0. Based on this, we conclude that metal center exchange on the surface does not proceed through a free‐base porphyrin as an intermediate. Furthermore, once formed, CuTPP is stable on the surface and the reverse exchange from CuTPP to ZnTPP in the presence of Zn2+ ions could not be achieved. The preference for copper is so strong that even an attempt to exchange adsorbed ZnTPP with Ni2+ ions in the presence of traces of Cu2+ yielded CuTPP rather than NiTPP. 相似文献
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Carl K. Brozek Dr. Luca Bellarosa Tomohiro Soejima Talia V. Clark Prof. Núria López Prof. Mircea Dincă 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):6871-6874
We investigated which factors govern the critical steps of cation exchange in metal–organic frameworks by studying the effect of various solvents on the insertion of Ni2+ into MOF‐5 and Co2+ into MFU‐4l. After plotting the extent of cation insertion versus different solvent parameters, trends emerge that offer insight into the exchange processes for both systems. This approach establishes a method for understanding critical aspects of cation exchange in different MOFs and other materials. 相似文献
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2‐(2′‐Bromophenyl)‐6‐butyl‐[1,3,6,2]dioxazaborocan, prepared readily by the esterification of 2‐bromophenylboronic acid with N‐butyldiethanolamine (BDEA), undergoes Br/Li exchange using BuLi/THF at ? 78 °C. A resulting intermediate proved useful in synthesis of various ortho‐functionalized arylboronic acids. Specifically, reactions with benzaldehydes provide a convenient access to 1,3‐dihydro‐1‐hydroxy‐3‐arylbenzo[c][2,1]oxaboroles that exhibit a remarkably high rotational barrier around the C? aryl bond. In addition, the molecular structure of sterically hindered 1,3‐dihydro‐1‐hydroxy‐3‐(2′, 6′‐dimethoxyphenyl)benzo[c][2,1]oxaborole is reported. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Arif Music Clment Hoarau Nicolas Hilgert Florian Zischka Dorian Didier 《Angewandte Chemie (International ed. in English)》2019,58(4):1188-1192
Described is the in situ formation of triorganocerium reagents and their application in catalyst‐free Zweifel olefinations. These unique cerium species were generated through novel exchange reactions of organohalides with n‐Bu3Ce reagents. The adequate electronegativity of cerium allowed for compensating the disadvantages of both usually functional‐group‐sensitive organolithium species and less reactive organomagnesium reagents. Exchange reactions were performed on aryl and alkenyl bromides, enabling enantiospecific transformations of chiral boron pinacol esters. Finally, these new organocerium species were engaged in selective 1,2‐additions onto enolisable and sterically hindered ketones. 相似文献
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Post‐Synthetic Ligand Exchange in Zirconium‐Based Metal–Organic Frameworks: Beware of The Defects! 下载免费PDF全文
Dr. Marco Taddei Dr. Russell J. Wakeham Athanasios Koutsianos Dr. Enrico Andreoli Prof. Andrew R. Barron 《Angewandte Chemie (International ed. in English)》2018,57(36):11706-11710
Post‐synthetic ligand exchange in the prototypical zirconium‐based metal–organic framework (MOF) UiO‐66 was investigated by in situ solution 1H NMR spectroscopy. Samples of UiO‐66 having different degrees of defectivity were exchanged using solutions of several terephthalic acid analogues in a range of conditions. Linker exchange only occurred in defect‐free UiO‐66, whereas monocarboxylates grafted at defect sites were found to be preferentially exchanged with respect to terephthalic acid over the whole range of conditions investigated. A 1:1 exchange ratio between the terephthalic acid analogue and modulator was observed, providing evidence that the defects had missing‐cluster nature. Ex situ characterisation of the MOF powders after exchange corroborated these findings and showed that the physical‐chemical properties of the MOF depend on whether the functionalisation occurs at defective sites or on the framework. 相似文献