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1.
Alexandre Genoux Jorge A. Gonzlez Estíbaliz Merino Cristina Nevado 《Angewandte Chemie (International ed. in English)》2020,59(41):17881-17886
A new family of phosphine‐ligated dicyanoarylgold(III) complexes has been prepared and their reactivity towards reductive elimination has been studied in detail. Both, a highly positive entropy of activation and a primary 12/13C KIE suggest a late concerted transition state while Hammett analysis and DFT calculations indicate that the process is asynchronous. As a result, a distinct mechanism involving an asynchronous concerted reductive elimination for the overall C(sp2)?C(sp)N bond forming reaction is characterized herein, for the first time, complementing previous studies reported for C(sp3)?C(sp3), C(sp2)?C(sp2), and C(sp3)?C(sp2) bond formation processes taking place on gold(III) species. 相似文献
2.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(42):13078-13082
The robust, high‐valent NiIV complex [(Py)2NiIVF2(CF3)2] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X‐ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 °C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric NiIIICF3 complexes 2 ⋅Py and 2 were identified as key intermediates, and their structures were unambiguously determined by EPR spectroscopy and X‐ray diffraction. Preliminary kinetic studies in combination with the isolation of reaction intermediates confirmed that the C−H bond‐breaking/C−CF3 bond‐forming sequence can occur both at NiIVCF3 and NiIIICF3 centers. 相似文献
3.
《Angewandte Chemie (International ed. in English)》2017,56(42):12898-12902
The robust, high‐valent NiIV complex [(Py)2NiIVF2(CF3)2] (Py=pyridine) was synthesized and fully characterized by NMR spectroscopy, X‐ray diffraction, and elemental analysis. It reacts with aromatic compounds at 25 °C to form the corresponding benzotrifluorides in nearly quantitative yield. The monomeric and dimeric NiIIICF3 complexes 2 ⋅Py and 2 were identified as key intermediates, and their structures were unambiguously determined by EPR spectroscopy and X‐ray diffraction. Preliminary kinetic studies in combination with the isolation of reaction intermediates confirmed that the C−H bond‐breaking/C−CF3 bond‐forming sequence can occur both at NiIVCF3 and NiIIICF3 centers. 相似文献
4.
Dr. Xiaoming Wang Dr. Da‐Gang Yu Prof. Dr. Frank Glorius 《Angewandte Chemie (International ed. in English)》2015,54(35):10280-10283
The first Cp*RhIII‐catalyzed arylation of unactivated C(sp3)? H bonds is presented. The unactivated primary C(sp3)? H bond of 2‐alkylpyridines can be activated by RhIII and further reacts with triarylboroxines to efficiently build new C(sp3)? aryl bonds. The methodology also provides a facile and efficient synthesis of unsymmetrical triarylmethanes by RhIII‐catalyzed C(sp3)? H arylation of diarylmethanes. 相似文献
5.
Megan MohadjerBeromi Gary W. Brudvig Nilay Hazari Hannah M. C. Lant Brandon Q. Mercado 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6155-6159
A number of new transition metal catalyzed methods for the formation of C(sp2)–C(sp3) bonds have recently been described. These reactions often utilize bidentate polypyridyl‐ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl‐ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2)–C(sp3) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2)–C(sp3) coupling through stoichiometric studies and also explore their catalytic activity. 相似文献
6.
Zehai Lu He Liu Shihan Liu Xuebing Leng Yu Lan Qilong Shen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(25):8598-8602
The synthesis, characterization, and C(sp2)?CF3 reductive elimination of stable aryl[tris(trifluoromethyl)]cuprate(III) complexes [nBu4N][Cu(Ar)(CF3)3] are described. Mechanistic investigations, including kinetic studies, studies of the effect of temperature, solvent, and the para substituent of the aryl group, as well as DFT calculations, suggest that the C(sp2)?CF3 reductive elimination proceeds through a concerted carbon–carbon bond‐forming pathway. 相似文献
7.
Zehai Lu He Liu Shihan Liu Xuebing Leng Yu Lan Qilong Shen 《Angewandte Chemie (International ed. in English)》2019,58(25):8510-8514
The synthesis, characterization, and C(sp2)?CF3 reductive elimination of stable aryl[tris(trifluoromethyl)]cuprate(III) complexes [nBu4N][Cu(Ar)(CF3)3] are described. Mechanistic investigations, including kinetic studies, studies of the effect of temperature, solvent, and the para substituent of the aryl group, as well as DFT calculations, suggest that the C(sp2)?CF3 reductive elimination proceeds through a concerted carbon–carbon bond‐forming pathway. 相似文献
8.
Mechanistic Insights into the Ni‐Catalyzed Reductive Carboxylation of C−O Bonds in Aromatic Esters with CO2: Understanding Remarkable Ligand and Traceless‐Directing‐Group Effects
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Yan‐Li Han Bing‐Yuan Zhao Kun‐Yao Jiang Hui‐Min Yan Dr. Zhu‐Xia Zhang Dr. Wen‐Jing Yang Prof. Dr. Zhen Guo Prof. Dr. Yan‐Rong Li 《化学:亚洲杂志》2018,13(12):1570-1581
The mechanism of the Ni0‐catalyzed reductive carboxylation reaction of C(sp2)?O and C(sp3)?O bonds in aromatic esters with CO2 to access valuable carboxylic acids was comprehensively studied by using DFT calculations. Computational results revealed that this transformation was composed of several key steps: C?O bond cleavage, reductive elimination, and/or CO2 insertion. Of these steps, C?O bond cleavage was found to be rate‐determining, and it occurred through either oxidative addition to form a NiII intermediate, or a radical pathway that involved a bimetallic species to generate two NiI species through homolytic dissociation of the C?O bond. DFT calculations revealed that the oxidative addition step was preferred in the reductive carboxylation reactions of C(sp2)?O and C(sp3)?O bonds in substrates with extended π systems. In contrast, oxidative addition was highly disfavored when traceless directing groups were involved in the reductive coupling of substrates without extended π systems. In such cases, the presence of traceless directing groups allowed for docking of a second Ni0 catalyst, and the reactions proceed through a bimetallic radical pathway, rather than through concerted oxidative addition, to afford two NiI species both kinetically and thermodynamically. These theoretical mechanistic insights into the reductive carboxylation reactions of C?O bonds were also employed to investigate several experimentally observed phenomena, including ligand‐dependent reactivity and site‐selectivity. 相似文献
9.
Regioselective CF Bond Activation of Hexafluoropropylene on Palladium(0): Formation of a Cationic η2‐Perfluoroallylpalladium Complex
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Dr. Masato Ohashi Mitsutoshi Shibata Prof. Dr. Sensuke Ogoshi 《Angewandte Chemie (International ed. in English)》2014,53(49):13578-13582
A chemoselective C(sp2)? F or C(sp3)? F bond activation of hexafluoropropylene (HFP) was achieved by adopting the proper combination of a Lewis acid co‐additive with a ligand which coordinates Pd0. The treatment of [(η2‐HFP)Pd(PCy3)2] with B(C6F5)3 allowed a chemoselective C(sp3)? F bond cleavage of HFP to give a unique cationic perfluoroallypalladium complex. In this complex, the coordination mode of the perfluoroallyl ligand was considered to be of the unique η2‐fashion. 相似文献
10.
N−N Bond Forming Reductive Elimination via a Mixed‐Valent Nickel(II)–Nickel(III) Intermediate
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Justin B. Diccianni Dr. Chunhua Hu Prof. Dr. Tianning Diao 《Angewandte Chemie (International ed. in English)》2016,55(26):7534-7538
Natural products containing N–N bonds exhibit important biological activity. Current methods for constructing N?N bonds have limited scope. An advanced understanding of the fundamental N?N bond formation/cleavage processes occurring at the transition‐metal center would facilitate the development of catalytic reactions. Herein we present an N?N bond‐forming reductive elimination, which proceeds via a mixed‐valent NiII–NiIII intermediate with a Ni–Ni bond order of zero. The discrete NiII–NiIII oxidation states contrast with the cationic dimeric Ni analogue, in which both Ni centers are equivalent with an oxidation state of 2.5. The electronic structures of these mixed‐valent complexes have implications for the fundamental understanding of metal–metal bonding interactions. 相似文献
11.
Mechanism of Nickel(II)‐Catalyzed Oxidative C(sp2)−H/C(sp3)−H Coupling of Benzamides and Toluene Derivatives
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The Ni‐catalyzed C(sp2)?H/C(sp3)?H coupling of benzamides with toluene derivatives was recently successfully achieved with mild oxidant iC3F7I. Herein, we employ density functional theory (DFT) methods to resolve the mechanistic controversies. Two previously proposed mechanisms are excluded, and our proposed mechanism involving iodine‐atom transfer (IAT) between iC3F7I and the NiII intermediate was found to be more feasible. With this mechanism, the presence of a carbon radical is consistent with the experimental observation that (2,2,6,6‐tetramethylpiperidin‐1‐yl)oxyl (TEMPO) completely quenches the reaction. Meanwhile, the hydrogen‐atom abstraction of toluene is irreversible and the activation of the C(sp2)?H bond of benzamides is reversible. Both of these conclusions are in good agreement with Chatani's deuterium‐labeling experiments. 相似文献
12.
Construction of Hexahydrophenanthrenes By Rhodium(I)‐Catalyzed Cycloisomerization of Benzylallene‐Substituted Internal Alkynes through C−H Activation
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Yasuaki Kawaguchi Dr. Shigeo Yasuda Prof. Dr. Chisato Mukai 《Angewandte Chemie (International ed. in English)》2016,55(35):10473-10477
The treatment of benzylallene‐substituted internal alkynes with [RhCl(CO)2]2 effects a novel cycloisomerization by C(sp2)?H bond activation to produce hexahydrophenanthrene derivatives. The reaction likely proceeds through consecutive formation of a rhodabicyclo[4.3.0] intermediate, σ‐bond metathesis between the C(sp2)?H bond on the benzene ring and the C(sp2)?RhIII bond, and isomerization between three σ‐, π‐, and σ‐allylrhodium(III) species, which was proposed based on experiments with deuterated substrates. 相似文献
13.
《Angewandte Chemie (International ed. in English)》2017,56(13):3635-3639
Metal–metal bonds play a vital role in stabilizing key intermediates in bond‐formation reactions. We report that binuclear benzo[h ]quinoline‐ligated NiII complexes, upon oxidation, undergo reductive elimination to form carbon–halogen bonds. A mixed‐valent Ni(2.5+)–Ni(2.5+) intermediate is isolated. Further oxidation to NiIII, however, is required to trigger reductive elimination. The binuclear NiIII–NiIII intermediate lacks a Ni−Ni bond. Each NiIII undergoes separate, but fast reductive elimination, giving rise to NiI species. The reactivity of these binuclear Ni complexes highlights the fundamental difference between Ni and Pd in mediating bond‐formation processes. 相似文献
14.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(13):3689-3693
Metal–metal bonds play a vital role in stabilizing key intermediates in bond‐formation reactions. We report that binuclear benzo[h ]quinoline‐ligated NiII complexes, upon oxidation, undergo reductive elimination to form carbon–halogen bonds. A mixed‐valent Ni(2.5+)–Ni(2.5+) intermediate is isolated. Further oxidation to NiIII, however, is required to trigger reductive elimination. The binuclear NiIII–NiIII intermediate lacks a Ni−Ni bond. Each NiIII undergoes separate, but fast reductive elimination, giving rise to NiI species. The reactivity of these binuclear Ni complexes highlights the fundamental difference between Ni and Pd in mediating bond‐formation processes. 相似文献
15.
Direct Cross‐Coupling of Allylic C(sp3)−H Bonds with Aryl‐ and Vinylbromides by Combined Nickel and Visible‐Light Catalysis
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Dr. Long Huang Prof. Dr. Magnus Rueping 《Angewandte Chemie (International ed. in English)》2018,57(32):10333-10337
An efficient protocol for the direct allylic C(sp3)?H bond activation of unactivated tri‐ and tetrasubstituted alkenes and their functionalization with aryl‐ and vinylbromides by nickel and visible‐light photocatalysis has been developed. The method allows C(sp2)?C(sp3) formation under mild reaction conditions with good functional‐group tolerance and excellent regioselectivity. 相似文献
16.
RhIII‐Catalyzed C(sp3)H Bond Activation by an External Base Metalation/Deprotonation Mechanism: A Theoretical Study
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Dr. Julong Jiang Dr. Romain Ramozzi Prof. Keiji Morokuma 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(31):11158-11164
The C(sp3)?H bond activation of 8‐methylquinoline followed by alkyne insertion catalyzed by a RhIII complex has been studied by using density functional theory (DFT) calculations. Contrary to common belief, the C?H bond activation of methylquinoline does not occur by the traditional intramolecular concerted metalation/deprotonation (CMD) mechanism but by an external base CMD mechanism. The use of free acetate or copper(II) acetate as base permits the C?H activation step, as observed experimentally. However, the following insertion is possible only if copper(II) acetate is used. The insertion followed by metathesis occurs via a cationic RhIII complex and is irreversible, which ensures the efficiency of the entire process. Therefore the use of copper is crucial for completing the catalytic cycle. The present work should help to rationalize the origins of the experimental results described in the literature. 相似文献
17.
Dr. Candice L. Joe Prof. Abigail G. Doyle 《Angewandte Chemie (International ed. in English)》2016,55(12):4040-4043
Using nickel and photoredox catalysis, the direct functionalization of C(sp3)?H bonds of N‐aryl amines by acyl electrophiles is described. The method affords a diverse range of α‐amino ketones at room temperature and is amenable to late‐stage coupling of complex and biologically relevant groups. C(sp3)?H activation occurs by photoredox‐mediated oxidation to generate α‐amino radicals which are intercepted by nickel in catalytic C(sp3)?C coupling. The merger of these two modes of catalysis leverages nickel's unique properties in alkyl cross‐coupling while avoiding limitations commonly associated with transition‐metal‐mediated C(sp3)?H activation, including requirements for chelating directing groups and high reaction temperatures. 相似文献
18.
CH Activation of Benzene by a Photoactivated NiII(azide): Formation of a Transient Nickel Nitrido Complex
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Vincent Vreeken Dr. Maxime A. Siegler Prof. Dr. Bas de Bruin Prof. Dr. Joost N. H. Reek Dr. Martin Lutz Dr. Ir. Jarl Ivar van der Vlugt 《Angewandte Chemie (International ed. in English)》2015,54(24):7055-7059
Photochemical activation of nickel‐azido complex 2 [Ni(N3)(PNP)] (PNHP=2,2′‐di(isopropylphosphino)‐4,4′‐ditolylamine) in neat benzene produces diamagnetic complex 3 [Ni(Ph)(PNPNH)], which is crystallographically characterized. DFT calculations support photoinitiated N2‐loss of the azido complex to generate a rare, transient NiIV nitrido species, which bears significant nitridyl radical character. Subsequent trapping of this nitrido through insertion into the Ni? P bond generates a coordinatively unsaturated NiII imidophosphorane P?N donor. This species shows unprecedented reactivity toward 1,2‐addition of a C? H bond of benzene to form 3 . The structurally characterized chlorido complex 4 [Ni(Cl)(PNPNH)] is generated by reaction of 3 with HCl or by direct photolysis of 2 in chlorobenzene. This is the first report of aromatic C? H bond activation by a trapped transient nitrido species of a late transition metal. 相似文献
19.
Robert Szpera Daniel F. J. Moseley Lewis B. Smith Alistair J. Sterling Vronique Gouverneur 《Angewandte Chemie (International ed. in English)》2019,58(42):14824-14848
This Review summarizes advances in fluorination by C(sp2)?H and C(sp3)?H activation. Transition‐metal‐catalyzed approaches championed by palladium have allowed the installation of a fluorine substituent at C(sp2) and C(sp3) sites, exploiting the reactivity of high‐oxidation‐state transition‐metal fluoride complexes combined with the use of directing groups (some transient) to control site and stereoselectivity. The large majority of known methods employ electrophilic fluorination reagents, but methods combining a nucleophilic fluoride source with an oxidant have appeared. External ligands have proven to be effective for C(sp3)?H fluorination directed by weakly coordinating auxiliaries, thereby enabling control over reactivity. Methods relying on the formation of radical intermediates are complementary to transition‐metal‐catalyzed processes as they allow for undirected C(sp3)?H fluorination. To date, radical C?H fluorinations mainly employ electrophilic N?F fluorination reagents but a unique MnIII‐catalyzed oxidative C?H fluorination using fluoride has been developed. Overall, the field of late‐stage nucleophilic C?H fluorination has progressed much more slowly, a state of play explaining why C?H 18F‐fluorination is still in its infancy. 相似文献
20.
A Preliminary Study of Diastereoselectivity in the PdII‐Catalyzed C(sp3)‐H Alkoxylation of Cyclic Systems
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Xinglin Yang Tian‐Yu Sun Prof. Yu Rao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3273-3277
Primary mechanism of a PdII‐catalyzed 8‐aminoquinoline‐directed C?H alkoxylation was investigated. It was understood that the PdII‐catalyzed C(sp3)?O bond formation proceeded through a concerted reductive elimination from the PdIV intermediate in the cyclic system. Deuteration experiments and related computational studies elucidate that intrinsic conformation determined the diastereoselectivity of the PdII‐catalyzed C?H alkoxylation of cyclic carboxylic acids. 相似文献