- Heterolytic bond activation at gold: Evidence for gold(iii) H-B, H-Si complexes, H-H and H-C cleavage
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The coordinatively unsaturated gold(iii) chelate complex [(C^N-CH)Au(C6F5)]+ (1+) reacts with main group hydrides H-BPin and H-SiEt3 in dichloromethane solution at -70 °C to form the corresponding σ-complexes, which were spectroscopically characterized (C^N-CH = 2-(C6H3But)-6-(C6H4But)pyridine anion; Pin = OCMe2CMe2O). In the presence of an external base such as diethyl ether, heterolytic cleavage of the silane H-Si bond leads to the gold hydrides [{(C^N-CH)AuC6F5}2(μ-H)]+ (2+) and (C^N-CH)AuH(C6F5) (5), together with spectroscopically detected [Et3Si-OEt2]+. The activation of dihydrogen also involves heterolytic H-H bond cleavage but requires a higher temperature (-20 °C). H2 activation proceeds in two mechanistically distinct steps: the first leading to 2 plus [H(OEt2)2]+, the second to protonation of one of the C^N pyridine ligands and reductive elimination of C6F5H. By comparison, formation of gold hydrides by cleavage of suitably activated C-H bonds is very much more facile; e.g. the reaction of 1·OEt2 with Hantzsch ester is essentially instantaneous and quantitative at -30 °C. This is the first experimental observation of species involved in the initial steps of gold catalyzed hydroboration, hydrosilylation and hydrogenation and the first demonstration of the ability of organic C-H bonds to act as hydride donors towards gold.
- Rocchigiani, Luca,Budzelaar, Peter H. M.,Bochmann, Manfred
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- The fluorine-pentafluorophenyl substitution reaction in anhydrous hydrogen fluoride (aHF): A new interesting methodical approach to synthesize pentafluorophenylxenonium salts
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In anhydrous hydrogen fluoride (aHF) (heterogeneous reaction) B(C6F5)3 transfers all the three aryl groups to XeF2 forming [C6F5Xe]+ salts. Upon addition of KF, the [C6F5Xe] [HF2] salt was isolated in 78.7% yield. [C6F5Xe] [HF2] dissolved in MeCN exhibits significant cation-anion interactions and decomposes within 14 days at 20°C. The acidity of the aHF solvent determines the nature of the products in the reaction of XeF2 with B(C6F5)3. The reaction path of this new methodical approach of fluorine-aryl substitution in aHF is discussed.
- Frohn, Hermann-Josef,Schroer, Thorsten
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- Synthesis and Reactivity of a Low-Coordinate Iron(II) Hydride Complex: Applications in Catalytic Hydrodefluorination
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A low-coordinate iron hydride complex bearing an unsymmetrical NpN (enamido-phosphinimine) ligand scaffold was synthesized and fully characterized. Insertion reactivity with azobenzene, 3-hexyne, and 1-azidoadamantane was explored, and the isolated products were analogous to previously reported β-diketiminate iron hydride insertion products. Surprisingly, the NpN iron hydride displays unprecedented reactivity toward hexafluorobenzene, affording an NpN iron fluoride complex and pentafluorobenzene as products. The NpN iron hydride is a precatalyst for catalytic hydro-defluorination of perfluorinated aromatics in the presence of silane. Kinetic studies indicated that the rate-determining step during catalysis involved silane.
- Hein, Nicholas M.,Pick, Fraser S.,Fryzuk, Michael D.
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- Promotion of reductive elimination reaction of diorgano(2,2′-bipyridyl)nickel(II) complexes by electron-accepting aromatic compounds, Lewis acids, and Bronsted acids
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Reductive elimination of R-R from dialkyl(2,2′-bipyridyl)nickel(II), [NiR2(bpy)] 1 (R = CH3 (1a), C2H5 (1b), n- C3H7 (1c)), caused by π-coordination of electron-accepting aromatic compounds and reductive elimination of Ar-Ar from [NiAr2(bpy)] 2 (Ar = C6F5 (2a) and pyrazolyls (2b and 2c)) promoted by electron-accepting aromatic compounds, Lewis acids, and Bronsted acids have been investigated. 1H-NMR and kinetic data indicate that π-coordination of the electron-accepting aromatic compound to [NiR2(bpy)] leads to the reductive elimination of R-R. The rate of the reductive elimination obeys the second-order rate law, -d[1]/dt = k[1][electron-accepting aromatic compound]. Plots of log k vs Σσp of the electron-accepting aromatic compound give a line with a slope of 1.8. Bronsted acids cause reductive elimination of Ar-Ar from 2 selectively under several reaction conditions (e.g., 2a with CF3COOH in air and 2b with HBr). The reductive elimination reaction of 2a caused by CF3COOH obeys the second-order rate law, -d[2a]/dt = k′[2a][CF3COOH], in air. The reaction of 2b with H2SO4 requires O2, giving the rate equation, -d[2b]/dt = k″[2b]2[O2]; k″ increases with [H2SO4], reaching a maximum value at a high [H2SO4]. UV-vis spectroscopy reveals the presence of the following equilibrium: 2b + H2SO4 ? 2b·H2SO4, and the equilibrium constant Ka is evaluated as Ka = [2b·H2SO4]/ ([2b][H2SO4]) = 47 M-1 at 300.5 K. UV-vis data give information about the electronic states of 2 and the 2b-Bronsted acid adduct. Poly(6-hexylpyridine-2,5-diyl) with a higher molecular weight has been prepared according to the basic information.
- Yamamoto, Takakazu,Abla, Mahmut,Murakami, Yasuharu
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- Promoting Difficult Carbon–Carbon Couplings: Which Ligand Does Best?
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A Pd complex, cis-[Pd(C6F5)2(THF)2] (1), is proposed as a useful touchstone for direct and simple experimental measurement of the relative ability of ancillary ligands to induce C?C coupling. Interestingly, 1 is also a good alternative to other precatalysts used to produce Pd0L. Complex 1 ranks the coupling ability of some popular ligands in the order PtBu3>o-TolPEWO-F≈tBuXPhos>P(C6F5)3≈PhPEWO-F>P(o-Tol)3≈THF≈tBuBrettPhos?Xantphos≈PhPEWO-H?PPh3according to their initial coupling rates, whereas their efficiency, depending on competitive hydrolysis, is ranked tBuXPhos≈PtBu3≈o-TolPEWO-F>PhPEWO-F>P(C6F5)3?tBuBrettPhos>THF≈P(o-Tol)3>Xantphos>PhPEWO-H?PPh3. This “meter” also detects some other possible virtues or complications of ligands such as tBuXPhos or tBuBrettPhos.
- Gioria, Estefanía,del Pozo, Juan,Martínez-Ilarduya, Jesús M.,Espinet, Pablo
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- The Pentafluorophenylxenon(II) Cation: +; The First Stable System with a Xenon-Carbon Bond
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Pentafluorophenylxenon(II) pentafluorophenyltrifluoroborate, +-, can be prepared analogously to pentafluorophenylhalogen(III) and (V) fluorides, C6F5HalF2 and C6F5HalF4 (with Hal=Br or I), by nucleophilic displacement of fluorine in XeF2 using B(C6F5)3 as an aryl-transfer reagent; the resulting colourless solid with a stable xenon-carbon bond is characterised in solution by (129)Xe and (19)F n.m.r. and chemically as an electrophilic transfer reagent for pentafluorophenyl groups.
- Frohn, Hermann J.,Jakobs, Stephanus
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- Reaction of difluoromethyl pentafluorophenyl sulfoxide with nucleophiles
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Reactions of 1-(difluoromethanesulfinyl)pentafluorobenzene with sodium methoxide, sodium phenoxide, potassium hydrosulfide, and methylamine resulted in substitution of fluorine atom in the 4-position (in the reaction with methylamine, also in the 2-positi
- Koshcheev,Maksimov,Platonov,Shelkovnikov
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- Grignard exchange reaction using a microflow system: From bench to pilot plant
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The Grignard exchange reaction of ethylmagnesium bromide (EtMgBr) and bromopentafluorobenzene (BPFB) to give pentafluorophenylmagnesium bromide (PFPMgBr) was carried out using small- and medium-scale microflow systems consisting of a micromixer and a microheat exchanger. The results indicate that the microflow systems are quite effective. On the basis of the data obtained, a pilot that involves the Toray Hi-mixer connected to a shell and tube microheat exchanger was constructed. Continuous operation for 24 h was accomplished without any problem to obtain pentafluorobenzene (PFB) after protonation (92% yield).
- Wakami, Hideo,Yoshida, Jun-Ichi
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- Reductive elimination of C6F5-C6F 5 in the reaction of bis(pentafluorophenyl)palladium(ii) complexes with protic acids
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Reductive elimination of C6F5-C6F 5 from cis-[Pd(C6F5)2L] (L = cod, bpy, and dppb) was promoted by Bronsted acids. HNO3 is a convenient acid for the formation of C6F5-C 6F5 from [Pd(C6F5) 2(cod)]. The products are controlled by the auxiliary ligand.
- Koizumi, Take-Aki,Yamazaki, Atsuko,Yamamoto, Takakazu
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- Synthesis, reactivity and X-ray crystal structure of tris(pentafluorophenyl)silanol (C6F5)3SiOH
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Tris(pentafluorophenyl)silanol (C6F5)3SiOH was prepared from the corresponding chlorosilane (C6F5)3SiCl by an unconventional controlled hydrolysis. The X-ray structure and the reactivity of
- Cariati, Elena,Carlucci, Lucia,D'Alfonso, Giuseppe,Giovenzana, Tommaso,Lucenti, Elena,Maggioni, Daniela,Sironi, Angelo
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- Photoredox catalysis on unactivated substrates with strongly reducing iridium photosensitizers
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Photoredox catalysis has emerged as a powerful strategy in synthetic organic chemistry, but substrates that are difficult to reduce either require complex reaction conditions or are not amenable at all to photoredox transformations. In this work, we show that strong bis-cyclometalated iridium photoreductants with electron-rich β-diketiminate (NacNac) ancillary ligands enable high-yielding photoredox transformations of challenging substrates with very simple reaction conditions that require only a single sacrificial reagent. Using blue or green visible-light activation we demonstrate a variety of reactions, which include hydrodehalogenation, cyclization, intramolecular radical addition, and prenylationviaradical-mediated pathways, with optimized conditions that only require the photocatalyst and a sacrificial reductant/hydrogen atom donor. Many of these reactions involve organobromide and organochloride substrates which in the past have had limited utility in photoredox catalysis. This work paves the way for the continued expansion of the substrate scope in photoredox catalysis.
- Shon, Jong-Hwa,Kim, Dooyoung,Rathnayake, Manjula D.,Sittel, Steven,Weaver, Jimmie,Teets, Thomas S.
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p. 4069 - 4078
(2021/04/06)
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- New catalytic systems with chemically fixed nickel complexes in the reactions of reductive activation of C-F bonds in ionic liquid media
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The nickel complexes with bidentate nitrogen-containing ligands covalently bound to alkylimidazolium cations were obtained for the first time. By the example of the reaction of selective hydrodefluorination of hexafluorobenzene to pentafluorobenzene, it was shown that the catalytic systems ionic liquid - water - covalently bound nickel complex based on the obtained compounds are much more efficient with repeated use in comparison with unfixed nickel complexes. The decisive influence of the cationic fragment of the ionic liquid on the possibility of multiple use of nickel complexes has been established.
- Adonin, N Yu,Prikhod'ko, S. A.,Shabalin, A Yu.
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- Catalytic Hydrodefluorination via Oxidative Addition, Ligand Metathesis, and Reductive Elimination at Bi(I)/Bi(III) Centers
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Herein, we report a hydrodefluorination reaction of polyfluoroarenes catalyzed by bismuthinidenes, Phebox-Bi(I) and OMe-Phebox-Bi(I). Mechanistic studies on the elementary steps support a Bi(I)/Bi(III) redox cycle that comprises C(sp2)-F oxidative addition, F/H ligand metathesis, and C(sp2)-H reductive elimination. Isolation and characterization of a cationic Phebox-Bi(III)(4-tetrafluoropyridyl) triflate manifests the feasible oxidative addition of Phebox-Bi(I) into the C(sp2)-F bond. Spectroscopic evidence was provided for the formation of a transient Phebox-Bi(III)(4-tetrafluoropyridyl) hydride during catalysis, which decomposes at low temperature to afford the corresponding C(sp2)-H bond while regenerating the propagating Phebox-Bi(I). This protocol represents a distinct catalytic example where a main-group center performs three elementary organometallic steps in a low-valent redox manifold.
- Cornella, Josep,Katzenburg, Felix,Leutzsch, Markus,N?thling, Nils,Pang, Yue
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supporting information
p. 12487 - 12493
(2021/08/30)
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- Stopped-Flow 19F NMR Spectroscopic Analysis of a Protodeboronation Proceeding at the Sub-Second Time-Scale
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In-situ NMR spectroscopic analysis of homogeneous reactions is an essential tool for mechanistic analysis in organic and organometallic chemistry. However, rapid non-equilibrium reactions, that are initiated by mixing, require specialized approaches. We report herein on a study of the factors that ensure quantitative results in a recently-developed technique for stopped-flow NMR spectroscopy. The influence of some of the key parameters on quantitation is studied by 19F NMR spectroscopic analysis of the kinetics and activation parameters for the base-catalyzed protodeboronation of highly-reactive polyfluorinated arylboronic acids, with half-lives as low as 0.1 seconds. The effects of spin relaxation, pre-magnetization, heat-transfer versus reaction enthalpy, and mixing-efficiency are analyzed in detail. We also compare and contrast choice of pulse angle, interscan delay, and use of pseudo real-time by interleaving, as means to achieve an optimal balance between temporal resolution and sensitivity.
- Wei, Ran,Hall, Andrew M. R.,Behrens, Richard,Pritchard, Mark S.,King, Edward J.,Lloyd-Jones, Guy C.
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supporting information
p. 2331 - 2342
(2021/05/03)
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- Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis
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The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)2→ ArB(OH)2) and protodeboronation (ArB(OR)2→ ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (19F,1H, and11B), pH-rate dependence, isotope entrainment,2H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pKaof the boronic acid/ester.
- Assante, Michele,Geogheghan, Katherine J.,Hayes, Hannah L. D.,Jin, Na,Leach, Andrew G.,Lloyd-Jones, Guy C.,Noonan, Gary,Tomasi, Simone,Wei, Ran
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supporting information
p. 14814 - 14826
(2021/09/13)
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- The aliphatic ring-opening and SNAr substitution in the reactions of perfluorobenzocycloalkenones with K2CO3 in water and methanol
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In the reactions with aqueous K2CO3, perfluorinated benzocyclobuten-1-one, 3-R-indan-1-ones and 4-R-tetralin-1-ones (R = F, C2F5) undergo selective cleavage of the СO–С(Ar) bond to yield (2,3,4,5-tetrafluorophen
- Zonov, Yaroslav V.,Wang, Siqi,Karpov, Victor M.,Mezhenkova, Tatyana V.
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- Convenient Synthesis of Symmetrical Polyfluorinated Diphenyl Sulfides
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Abstract: Thermal properties of decafluorodiphenyl disulfide in the pure state and in the presence of copper and iron metals have been studied. A procedure has been proposed for the synthesis of symmetrical poly-fluorinated diaryl sulfides from diaryl dis
- Bredikhin, R. A.,Maksimov, A. M.,Nikul’shin, P. V.,Platonov, V. E.
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p. 1921 - 1930
(2022/01/24)
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- Tailorable carbazolyl cyanobenzene-based photocatalysts for visible light-induced reduction of aryl halides
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Herein, a series of carbazolyl cyanobenzene (CCB)-based organic photocatalysts with a broad range of photoredox capabilities were designed and synthesized, allowing precise control of the photocatalytic reactivity for the controllable reduction of aryl halides via a metal-free process. The screened-out CCB (5CzBN), a metal-free, low-cost, scalable and sustainable photocatalyst with both strong oxidative and reductive ability, exhibits superior performance for both dehalogenation and C[sbnd]C bond-forming arylation reactions.
- Ou, Wei,Zou, Ru,Han, Mengting,Yu, Lei,Su, Chenliang
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supporting information
p. 1899 - 1902
(2019/12/27)
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- Light-driven activation of carbon-halogen bonds by readily available amines for photocatalytic hydrodehalogenation
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A straightforward protocol using readily available aromatic amines, N,N,N′,N′-tetramethyl- p-phenylenediamine or N,N′,N′-tetramethylbenzidine, as photocatalysts was developed for the efficient hydrodehalogenation of organic halides, such as 4′-bromoacetophenone, polyfluoroarenes, cholorobenzene, and 2,2′,4,4′-tetrabromodiphenyl ether(a resistant and persistent organic pollutant). The strongly reducing singlet excited states of the amines enabled diffusion-controlled dissociative electron transfer to effectively cleave carbon-halogen bonds, followed by radical hydrogenation. Diisopropylethylamine served as the terminal electron/proton donor and regenerated the amine sensitizers.
- Chen, Chuncheng,Duan, Ran,Meng, Di,Song, Wenjing,Wei, Yan,Zhao, Jincai,Zhen, Shengli,Zhu, Qian
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p. 1474 - 1479
(2020/04/29)
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- Direct Stereoselective β-Arylation of Enol Ethers by a Decarboxylative Heck-Type Reaction
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Despite remarkable advances to promote regio- and stereoselective decarboxylative arylation of inactivated olefins with benzoic acid derivatives, methodologies involving hetero-substituted alkenes are still lacking. Herein, PdII-catalyzed decarboxylative Heck coupling of α-alkoxyacrylates with (hetero)aryl carboxylic acids for the stereocontrolled production of (Z)-β-heteroarylated vinyl ethers is reported. This methodology offers a rational and step-economical route to the synthesis of attractive β-arylated α-alkoxy α,β-unsaturated carboxylates family which emerged as a relevant class of building blocks with different applications. Mechanistically, whereas electron rich benzoic acids undergo a PdII-catalyzed decarboxylation, electron-deficient substrates proceed through silver(I)-mediated decarboxylation, explaining thus the formation of stereoisomers (E) and (Z) of β-arylated vinyl ethers in presence of these latter.
- Hachem, Mahmoud,Hoarau, Christophe,Schneider, Cédric
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- Ranking Ligands by Their Ability to Ease (C6F5)2NiIIL → Ni0L + (C6F5)2Coupling versus Hydrolysis: Outstanding Activity of PEWO Ligands
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The NiII literature complex cis-[Ni(C6F5)2(THF)2] is a synthon of cis-Ni(C6F5)2 that allows us to establish a protocol to measure and compare the ligand effect on the NiII → Ni0 reductive elimination step (coupling), often critical in catalytic processes. Several ligands of different types were submitted to this Ni-meter comparison: Bipyridines, chelating diphosphines, monodentate phosphines, PR2(biaryl) phosphines, and PEWO ligands (phosphines with one potentially chelate electron-withdrawing olefin). Extremely different C6F5-C6F5 coupling rates, ranging from totally inactive (producing stable complexes at room temperature) to those inducing almost instantaneous coupling at 25 °C, were found for the different ligands tested. The PR2(biaryl) ligands, very efficient for coupling in Pd, are slow and inefficient in Ni, and the reason for this difference is examined. In contrast, PEWO type ligands are amazingly efficient and provide the lowest coupling barriers ever observed for NiII complexes; they yield up to 96% C6F5-C6F5 coupling in 5 min at 25 °C (the rest is C6F5H) and 100% coupling with no hydrolysis in 8 h at-22 to-53 °C.
- Ponce-De-León, Jaime,Gioria, Estefania,Martínez-Ilarduya, Jesús M.,Espinet, Pablo
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p. 18287 - 18294
(2020/12/23)
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- Site-selective redox isomerizations of furanosides using a combined arylboronic acid/photoredox catalyst system
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In the presence of an arylboronic acid and a hydrogen atom transfer mediator under photoredox conditions, furanoside derivatives undergo site-selective redox isomerizations to 2-keto-3-deoxyfuranosides. Experimental evidence and computational modeling suggest that the transformation takes place by abstraction of the hydrogen atom from the 2-position of the furanoside-derived arylboronic ester, followed by C3-O bond cleavage via spin-center shift. This mechanism is reminiscent of the currently accepted pathway for the formation of 3′-ketodeoxynucleotides by ribonucleotide reductase enzymes.
- Dimakos, Victoria,Gorelik, Daniel,Su, Hsin Y.,Garrett, Graham E.,Hughes, Gregory,Shibayama, Hiromitsu,Taylor, Mark S.
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p. 1531 - 1537
(2020/02/25)
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- Structures and Stability of Complexes of E(C6F5)3 (E = B, Al, Ga, In) with Acetonitrile
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Complexes formed by interaction of E(C6F5)3 (E = B, Al, Ga, In) with excess of acetonitrile (AN) were structurally characterized. Quantum chemical computations indicate that for Al(C6F5)3 and In(C6F5)3 the formation of a complex of 1:2 composition is more advantageous than for B(C6F5)3 and Ga(C6F5)3, in line with experimental observations. Formation of the solvate [Al(C6F5)3·2AN]·AN is in agreement with predicted thermodynamic instability of [Al(C6F5)3·3AN]. Tensimetry study of B(C6F5)3·CH3CN reveals its stability in the solid state up to 197 °C. With the temperature increase, the complex undergoes irreversible thermal decomposition with pentafluorobenzene formation.
- Shcherbina, Nadezhda A.,Pomogaeva, Anna V.,Lisovenko, Anna S.,Kazakov, Igor V.,Gugin, Nikita Yu.,Khoroshilova, Olesya V.,Kondrat'ev, Yuri V.,Timoshkin, Alexey Y.
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supporting information
p. 873 - 881
(2020/05/05)
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- B(C6F5)3- And HB(C6F5)2-mediated transformations of isothiocyanates
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This contribution reports on the reactivity of isothiocyanates towards the boranes B(C6F5)3and HB(C6F5)2. The reactions of alkyl-substituted isothiocyanates with B(C6F5)3were found to result in rearrangement reactions to yield stable thiocyanate-B(C6F5)3adducts. Treatment of isothiocyanates with HB(C6F5)2leads to 1,2-hydroboration and thus, B,N,C,S heterocycles are formed, which react further under non-inert conditions. Hydrolysis of the hydroboration products leads to a new access to thioformamides.
- Fischer, Malte,Schmidtmann, Marc
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supporting information
p. 6205 - 6208
(2020/06/22)
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- Rotation-Triggered Transmetalation on a Heterobimetallic Cu/Al N-Phosphine-Oxide-Substituted Imidazolylidene Complex
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A novel strategy for the preparation of heterobimetallic N-heterocyclic carbene (NHC) complexes is demonstrated using N-phosphine-oxide-substituted imidazolylidenes (PoxIms). In these heterobimetallic Cu/Al complexes, the Cu and Al centers can be either completely separated or brought near each other via the rotation of the N-phosphinoyl group in the PoxIm ligands. Triggered by this rotation, transmetalation to exchange the Cu-OtBu and Al-C6F5 bonds occurs on in situ-generated Cu/Al PoxIm complexes, and the Cu-C6F5 and Al-OtBu bonds are formed in excellent yield. On the basis of the results of mechanistic studies, including the isolation/in situ observation of key complexes and theoretical calculations, a plausible reaction mechanism for an intramolecular transmetalation is proposed to proceed via an activation complex that includes the simultaneous coordination of the phosphinoyl oxygen atom to the Cu as well as the Al centers. Furthermore, the formation of carbon-carbon bonds between Al(C6F5)3 and allyl bromide mediated/catalyzed by Cu/Al PoxIm complexes is demonstrated. Upon the consecutive transfer of three C6F5 groups from a single molecule of Al(C6F5)3, allyl pentafluorobenzene derivatives were obtained. The present results demonstrate the role of phosphine oxide in the activation of organoaluminum reagents for the transmetalation between Cu(I) complexes bearing NHCs as well as the benefit of constructing an intramolecular system based on a heterobimetallic complex to achieve efficient transmetalation by programming the encounter of two organometallic fragments.
- Asada, Takahiro,Hoshimoto, Yoichi,Ogoshi, Sensuke
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supporting information
p. 9772 - 9784
(2020/07/10)
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- Hydrodefluorination of functionalized fluoroaromatics with triethylphosphine: A theoretical and experimental study
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Recently we reported the metal free hydrodefluorination of selected fluoroaromatics using triethylphosphine as the sole defluorinating agent. That prompted us to evaluate the mechanistic proposal and in the light of these results, along with new experimental evidence, we have now modified the initial proposal. The new mechanism avoids the highly energetic β-elimination step of roughly 71 kcal mol-1 for hexafluorobenzene and pentafluoropyridine at 393.15 K, invoking the participation of water. The use of D2O confirmed the role of water as the hydrogen source, yielding the corresponding deutero-defluorinated products; DFT calculations agree with this new proposed mechanism. We also report herein the use of this one-pot hydrodefluorination method applied to a broader number of fluoroaromatic derivatives; some of them allowed the collection of key mechanistic evidence.
- Facundo, Aldo A.,Arévalo, Alma,Fundora-Galano, Gabriela,Flores-álamo, Marcos,Orgaz, Emilio,García, Juventino J.
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p. 6897 - 6908
(2019/05/17)
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- Hydrogen bonding promoted simple and clean photo-induced reduction of C-X bond with isopropanol
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We herein report a simple and clean photo-induced metal-free reduction of C-X bond under an atmosphere of air at room temperature. Isopropanol is used as both the reducing reagent and solvent. Various functional groups (acids, esters, alcohols, anilines, phenols, indoles, pyridines, cyano and trifluoromethyl groups) and other heterocyclic compounds are tolerated. Different organic halides (including C-I, C-Br and C-Cl bonds) can be dehalogenated with moderate to excellent yields. Polyhalides are also reduced chemoselectively and efficiently. DFT calculation suggests a six-membered ring transition state via C-X H-O hydrogen bonding to decrease the activation energy.
- Cao, Dawei,Yan, Chaoxian,Zhou, Panpan,Zeng, Huiying,Li, Chao-Jun
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supporting information
p. 767 - 770
(2019/01/21)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- Transmetalation of Pentafluorophenylmercury Derivatives with Organylmagnesium Bromides
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The reactions of pentafluorophenylmercury derivatives with organomagnesium compounds have been studied. The interaction of pentafluorophenylmercury chloride with RMgBr (R = Et, Ph) has afforded diphenyl- and diethylmercury or phenylmercury chloride, besides the expected product (C6F5HgR). The results have been explained by the transmetalation of C6F5HgR with the Grignard reagent, followed by the reaction of the resulting C6F5MgX (X = Br, C6F5) with pentafluorophenylmercury chloride. Transmetalation of (C6F5)2Hg with organylmagnesium bromides has led to the formation of C6F5MgX and R2Hg.
- Bardin
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p. 1406 - 1408
(2019/08/21)
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- The preparation of pentafluorophenyldihaloboranes from pentafluorophenylmercurials C6F5HgR and BX3: the dramatic dependence of the reaction direction on the ligand R
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Abstract: In search of convenient preparations of C6F5BX2 (X = Cl, Br), reactions of C6F5HgR (R = C6F5, C6H5, C2H5, Br and Cl) with BX3 were studied. Under the action of BCl3 the order of the C–Hg bond cleavage is C6F5Hg–C6H5 > C6F5–HgC2H5 > C6F5–HgC6F5 >> C6F5–HgCl. With more reactive BBr3 the sequence is C6F5Hg–C6H5 > C6F5–HgC2H5 ~ C6F5Hg–C2H5 > C6F5–HgC6F5 ≥ C6F5–HgBr. During the study we found the simple way to alkyldibromoboranes which is presented by the preparation of C2H5BBr2 from C2H5HgBr and BBr3. It is the second example of synthesis of alkylmercury derivative in an addition to the earlier reported formation of cyclopropylmercurials from di(cyclopropyl)mercury and BX3. Graphic abstract: [Figure not available: see fulltext.].
- Bardin, Vadim V.,Adonin, Nicolay Yu.
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p. 1523 - 1531
(2019/07/22)
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- E- Z Isomerization of Phosphine-Olefin (PEWO-F4) Ligands Revealed upon PdCl2 Capture: Facts and Mechanism
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The PEWO phosphines R2P(o-C6H4CH-CHC(O)Ph), R2P(o-C6H2F2CH-CHC(O)Ph), and R2P(o-C6F4CH-CHC(O)Ph) and their P-monodentate complexes trans-[PdCl2(P-monodentate)2] show, in solution and (when available) in the X-ray diffraction structures, an E configuration of the double bond. In contrast, the structures of [PdCl2(P-chelate)] display E and Z configurations. The E/Z isomerization of the latter requires first decoordination of the double bond, which then allows for easy rotation about the electron-deficient double bond. Thus, the E/Z equilibria exist for the free and the P-monodentate complexes as well but are not observed because they are extremely displaced toward the E isomer. Their capture in the form of [PdCl2(P-chelate)], with equilibrium constants on the order Keq ≈ 1-3, allows the two configurations to be observed and isolated. Evaluation of their ability to couple Pf-Pf from cis-[PdPf2(THF)2] (Pf = C6F5) affords values of their ΔG?(Pf-Pf)Pd parameters confirming that higher substitution of H by F produces lower coupling barriers and a double bond that is more electron deficient when it is free and more electron withdrawing when it is coordinated.
- Pe?as-Defrutos, Marconi N.,Vélez, Andrea,Gioria, Estefanía,Espinet, Pablo
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supporting information
p. 4701 - 4707
(2019/12/24)
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- Palladium-catalyzed salt-free double decarboxylative aryl allylation
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This report describes a palladium-catalyzed decarboxylative aryl allylation between unactivated benzoic acids and allylic carbonates. This transformation successfully couples a variety of carbonates and benzoic acids in good yield (up to 94%) using 1 mol% palladium. This salt free allyl-arylation proceeds without added base, copper, or silver. The only stoichiometric byproducts are carbon dioxide and tert-butanol.
- Daley, Ryan A.,Topczewski, Joseph J.
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supporting information
p. 1709 - 1713
(2019/02/20)
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- Preparation of heptafluoronaphthyllithiums and -magnesiums: An unexpected difference in the reactivity of isomers C10F7H and C10F7Br towards organolithium and organomagnesium compounds
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Significant differences in the reactivity of isomeric heptafluoronaphthalenes and bromoheptafluoronaphthalenes towards organolithium and organomagnesium compounds were found. Metalation of polyfluorinated naphthalenes 2-C10F7X (X = H, Br) occurs easily under the action of bases (BuLi, t-BuLi, LDA) as well as EtMgBr (X = Br) in ether. This fact was proven by 19F NMR spectroscopy and by trapping of 2-C10F7M (M = Li, MgBr, Mg(2-C10F7)) with electrophile ClSiMe3. The interaction of 1-C10F7Br with BuLi or EtMgBr proceeds in a similar way. In contrast to 2-C10F7H, isomeric 1-C10F7H is the less acidic substrate and undergoes only the nucleophilic alkyldefluorination when combined with BuLi or t-BuLi.
- Shmakov, Mikhail M.,Bardin, Vadim V.,Prikhod'ko, Sergey A.,Adonin, Nicolay Yu
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supporting information
(2019/08/20)
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- Method for reducing perfluorinated aromatic compound to partial fluorinated aromatic compound by utilizing photocatalysis
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The invention belongs to the technical field of photocatalytic synthesis, and particularly relates to a method for reducing perfluorinated aromatic compound to partial fluorinated aromatic compound byutilizing photocatalysis. The method comprises the step of performing illumination reaction on the perfluorinated aromatic compound in the existence of a photocatalyst to obtain the partial fluorinated aromatic compound. According to the method provided by the invention, the problems of a plurality of reaction processes, complicated operation, high energy consumption, long reaction time and the like in a reaction for preparing the partial fluorinated aromatic compound in the prior art are solved; the partial fluorinated aromatic compound can be synthesized highly efficiently and environmentally friendly. For example, a sacrificial agent used in the method can serve as a reaction solvent; the reaction is performed in illumination; the operation is simple.
- -
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Paragraph 0043-0058
(2018/07/30)
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- NHC·Alane Adducts as Hydride Sources in the Hydrodefluorination of Fluoroaromatics and Fluoroolefins
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We present herein the utilization of NHC-stabilized alane adducts of the type (NHC)·AlH3 [NHC = Me2Im (1), Me2ImMe (2), iPr2Im (3), iPr2ImMe (4), Dipp2Im (5)] and (NHC)·AliBu2H [NHC = iPr2Im (6), Dipp2Im (7)] as novel hydride transfer reagents in the hydrodefluorination (HDF) of different fluoroaromatics and hexafluoropropene. Depending on the alane adduct used, HDF of pentafluoropyridine to 2,3,5,6-tetrafluoropyridine in yields of 15–99 % was observed. The adducts 1, 2, and 5 achieved a quantitative conversion into 2,3,5,6-tetrafluoropyridine at room temperature immediately after mixing the reactants. Studies on the HDF of fluorobenzenes with the (NHC)·AlH3 adducts 1, 3, and 5 and (Dipp2Im)·AliBu2H (7) showed the decisive influence of the reaction temperature on the H/F exchange and that 135 °C in xylene afforded the best product distribution. Although the HDF of hexafluorobenzene yielded 1,2,4,5-tetrafluorobenzene in moderate yields with traces of 1,2,3,4-tetrafluorobenzene and 1,2,4-trifluorobenzene, pentafluorobenzene was converted quantitatively into 1,2,4,5-tetrafluorobenzene, with (Dipp2Im)·AliBu2H (7) showing the highest activity and reaching complete conversion after 12 h at 135 °C in xylene. The HDF of hexafluoropropene with (Me2Im)·AlH3 (1) occurred even at low temperatures and preferably at the CF2 group with the formation of 1,2,3,3,3-pentafluoropropene (with 0.4 equiv. of 1) or 2,3,3,3-tetra-fluoropropene (with 0.9 equiv. of 1) as the main product.
- Schneider, Heidi,Hock, Andreas,Jaeger, Alma D.,Lentz, Dieter,Radius, Udo
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p. 4031 - 4043
(2018/09/11)
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- Identifying the potential of pulsed LED irradiation in synthesis: Copper-photocatalysed C-F functionalisation
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It has been reported that pulsed irradiation can improve photosynthetic activity and phytochemical production in plants. Intrigued and inspired by these observations, we postulated that pulsed irradiation strategies may have broader implications in organic synthesis. We report here the results of a proof-of-concept study demonstrating that pulsed LED irradiation enhances the efficiency of a visible light-mediated photoredox-catalysed reaction. The design and construction of an inexpensive multiphase circuit (~US$5) enabling power and pulse frequency modulation, which is connected to light-emitting diodes (LEDs), provides a source of pulsed visible light. This technology was then utilised to establish a novel copper-photocatalysed dual α-amino C-H/C-F functionalisation reaction. Pulsed blue LED irradiation was shown to be crucial for facilitating a much more efficient process and increasing the rate of product formation. Our results suggest that pulsed irradiation strategies have the potential to contribute to enhancing the synthetic utility and extending the scope of first row transition metal-based photoredox catalysts. We also anticipate that this approach will find wider applications in synthesis.
- Nicholls, Thomas P.,Robertson, Johnathon C.,Gardiner, Michael G.,Bissember, Alex C.
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supporting information
p. 4589 - 4592
(2018/05/14)
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- Ni-Catalyzed Decarboxylative Cross-Coupling of Potassium Polyfluorobenzoates with Unactivated Phenol and Phenylmethanol Derivatives
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A Ni-catalyzed decarboxylative cross-coupling of potassium polyfluorobenzoates with unactivated phenol and phenylmethanol derivatives is described. This novel transformation provides a practical and efficient protocol towards the synthesis of important polyfluorobiaryls and polyfluorinated diarylmethanes, and greatly enlarges the range of electrophiles utilized in decarboxylative coupling. Remarkably, preliminary mechanistic studies indicated the essential role of Zn(OAc)2 might lie in the enhancement of decarboxylation step. (Figure presented.).
- Chen, Quan,Wu, Aizhen,Qin, Shengxiang,Zeng, Meiqi,Le, Zhiping,Yan, Zhaohua,Zhang, Hua
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p. 3239 - 3244
(2018/09/10)
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- [2,2′-bipyridin]-6(1 H)-one, a Truly Cooperating Ligand in the Palladium-Mediated C-H Activation Step: Experimental Evidence in the Direct C-3 Arylation of Pyridine
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The ligand [2,2′-bipyridin]-6(1H)-one (bipy-6-OH) has a strong accelerating effect on the Pd-catalyzed direct arylation of pyridine or arenes. The isolation of relevant intermediates and the study of their decomposition unequivocally show that the deprotonated coordinated ligand acts as a base and assists the cleavage of the C-H bond. Mechanistic work indicates that the direct arylation of pyridine with this ligand occurs through a Pd(0)/Pd(II) cycle. Because of this dual ligand-intramolecular base role, there is no need for an available coordination site on the metal for an external base, a difficulty encountered when chelating ligands are used in coupling reactions that involve a C-H cleavage step.
- Salamanca, Vanesa,Toledo, Alberto,Albéniz, Ana C.
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p. 17851 - 17856
(2019/01/04)
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- Interactions of C?F Bonds with Hydridoboranes: Reduction, Borylation and Friedel–Crafts Alkylation
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The stoichiometric reactions of the alkylfluorides 1-fluoroadamantane (Ad-F), fluorocyclohexane (Cy-F), 1-fluoropentane (Pent-F) and benzyl fluorides with secondary boranes pinacolborane (HBpin), catecholborane (HBcat), 9-borabicyclo(3.3.1)nonane (9-BBN)
- Bamford, Karlee L.,Chitnis, Saurabh S.,Qu, Zheng-wang,Stephan, Douglas W.
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supporting information
p. 16014 - 16018
(2018/10/15)
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- Room Temperature Regioselective Catalytic Hydrodefluorination of Fluoroarenes with trans-[Ru(NHC)4H2] through a Concerted Nucleophilic Ru?H Attack Pathway
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The efficient and highly selective room temperature hydrodefluorination (HDF) of fluoroarenes by the trans-[Ru(IMe4)4H2] catalyst, 3, is reported. Mechanistic studies show 3 acts directly in catalysis without any ligand dissociation and DFT calculations indicate a concerted nucleophilic attack mechanism. The calculations fully account for the observed selectivities which corroborate earlier predictions regarding the selectivity of HDF.
- Cybulski, Mateusz K.,McKay, David,Macgregor, Stuart A.,Mahon, Mary F.,Whittlesey, Michael K.
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p. 1515 - 1519
(2017/02/05)
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- Preparation method of pentafluorophenol
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The invention relates to the field of organic synthesis and in particular relates to a preparation method of pentafluorophenol. The structural formula of pentafluorophenol is as shown in a formula I. The preparation method specifically comprises the following steps of: (1) decarboxylic reaction; (2) Grignard reaction; and (3) oxidizing reaction. According to the preparation method of pentafluorophenol, raw materials are easily available and are low in cost, the production cost is low, the waste of bromine resources is avoided, and adverse effects on the environment are reduced; meanwhile, the preparation method of pentafluorophenol is mild in reaction condition, high in process safety, few in product impurity, easy in extraction and purification and stable in quality; and the content of pentafluorophenol obtained by refining is greater than 99%, so that the preparation method is completely suitable for large-scale industrial production.
- -
-
Paragraph 0082-0083; 0086-0087; 0091; 0095; 0099
(2017/08/29)
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- Method for preparing 2,3,4,5,6-pentafluorophenol
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The invention discloses a method for preparing 2,3,4,5,6-pentafluorophenol. The method comprises the following step of in water, performing an oxidation reaction on 2,3,4,5,6-pentafluoro phenylboronic acid as shown in the formula (VI) and hydrogen peroxide, thereby obtaining 2,3,4,5,6-pentafluorophenol as shown in the formula (VII). According to the method, an oxidation reaction is implemented in the water, so that the method is low in cost, and environmental-friendly; and besides, the method is high in reaction yield and purity and relatively applicable to industrial production.
- -
-
Paragraph 0094; 0095
(2017/08/29)
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- Transition-Metal-Free Catalytic Hydrodefluorination of Polyfluoroarenes by Concerted Nucleophilic Aromatic Substitution with a Hydrosilicate
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A transition-metal-free catalytic hydrodefluorination (HDF) reaction of polyfluoroarenes is described. The reaction involves direct hydride transfer from a hydrosilicate as the key intermediate, which is generated from a hydrosilane and a fluoride salt. The eliminated fluoride regenerates the hydrosilicate to complete the catalytic cycle. Dispersion-corrected DFT calculations indicated that the HDF reaction proceeds through a concerted nucleophilic aromatic substitution (CSNAr) process.
- Kikushima, Kotaro,Grellier, Mary,Ohashi, Masato,Ogoshi, Sensuke
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supporting information
p. 16191 - 16196
(2017/11/27)
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- Unexpected distinction in reactivity of pentafluorobenzenesulfonyl halides toward organolithiums and organomagnesium halides
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C6F5SO2Cl reacts with organolithiums and organomagnesium halides RM (R = Me, Bu, Ph; M = Li, MgX) to give mainly C6F5H and C6F5Cl. C6F5SO2Br and
- Bardin, Vadim V.,Maksimov, Alexander M.
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p. 731 - 737
(2017/10/16)
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- Gold-Catalyzed Direct Oxidative Arylation with Boron Coupling Partners
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An efficient synthesis of biaryls through a gold-catalyzed oxidative cross-coupling of arenes with strong electron-deprived aryl boronates is presented herein. Regio- and chemocontrol are achieved by the selective activation of these coupling partners by gold at different oxidation states. Under reaction conditions devoid of basic additives or directing groups, the role of acetato ligand as an internal base has been revealed as a key parameter for expanding the reaction scope in these transformations.
- Hofer, Manuel,Genoux, Alexandre,Kumar, Roopender,Nevado, Cristina
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supporting information
p. 1021 - 1025
(2017/01/18)
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- Base-Catalyzed Aryl-B(OH)2 Protodeboronation Revisited: From Concerted Proton Transfer to Liberation of a Transient Aryl Anion
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Pioneering studies by Kuivila, published more than 50 years ago, suggested ipso protonation of the boronate as the mechanism for base-catalyzed protodeboronation of arylboronic acids. However, the study was limited to UV spectrophotometric analysis under acidic conditions, and the aqueous association constants (Ka) were estimated. By means of NMR, stopped-flow IR, and quenched-flow techniques, the kinetics of base-catalyzed protodeboronation of 30 different arylboronic acids has now been determined at pH > 13 in aqueous dioxane at 70 °C. Included in the study are all 20 isomers of C6HnF(5-n)B(OH)2 with half-lives spanning 9 orders of magnitude: a and Sδ values, kinetic isotope effects (2H, 10B, 13C), linear free-energy relationships, and density functional theory calculations, we have identified a mechanistic regime involving unimolecular heterolysis of the boronate competing with concerted ipso protonation/C-B cleavage. The relative Lewis acidities of arylboronic acids do not correlate with their protodeboronation rates, especially when ortho substituents are present. Notably, 3,5-dinitrophenylboronic acid is orders of magnitude more stable than tetra-and pentafluorophenylboronic acids but has a similar pKa.
- Cox, Paul A.,Reid, Marc,Leach, Andrew G.,Campbell, Andrew D.,King, Edward J.,Lloyd-Jones, Guy C.
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supporting information
p. 13156 - 13165
(2017/09/26)
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- Replacing C6F5 groups with Cl and H atoms in frustrated Lewis pairs: H2 additions and catalytic hydrogenations
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2-(Dialkylamino)phenylboranes containing the BXZ group, where X, Z = C6F5, Cl, and H, were prepared in a few synthetic steps and demonstrated the cleavage of H2 under mild conditions. Depending on the nature of the dialkylamino group, X, and Z, the stability of the produced zwitterionic H2 adducts varies from isolated solids indefinitely stable in an inert atmosphere to those quickly equilibrating with the initial aminoborane and H2. Using a combined experimental/computational approach on a series of isostructural aminoboranes (dialkylamino = 2,2,6,6-tetramethylpiperid-1-yl), it was demonstrated that the electronegativity and the steric effect of the substituents generally follow the trend C6F5 ~ Cl ? H. This observation is useful for designing new FLPs for practical applications. As an example, we demonstrated the hydrogenation of alkynes to cis-alkenes under mild conditions that was catalyzed by a chloro-analogue of the C6F5-substituted aminoborane developed previously. The presence of a BHCl group in the aminochloroboranes or in their H2 adducts features facile redistribution of the H and Cl atoms and the formation of polychloro and polyhydrido species.
- Chernichenko,Kótai,Nieger,Heikkinen,Pápai,Repo
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supporting information
p. 2263 - 2269
(2017/02/26)
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- Catalytic Hydrodefluorination of Fluoroarenes Using Ru(IMe4)2L2H2 (IMe4 = 1,3,4,5-Tetramethylimidazol-2-ylidene; L2 = (PPh3)2, dppe, dppp, dppm) Complexes
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The all-trans isomer of Ru(IMe4)2(PPh3)2H2 (ttt-4; IMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) reacts with C6F6 at 70 °C to afford the hydride fluoride complex Ru(IMe4)2(PPh3)2HF (ttt-6). At room temperature, ttt-6 reacts with Et3SiH to give a mixture of products, one of which is assigned as the silyl trihydride complex Ru(IMe4)2(PPh3)(SiEt3)H3 (8) by comparison to the isolated and structurally characterized analogue Ru(IMe4)2(PPh3)(SiPh3)H3 (9). As ttt-4 was re-formed cleanly upon heating ttt-6 with Et3SiH, it was tested in the catalytic hydrodefluorination (HDF) of C6F6 (10 mol %, 90 °C), along with 9, Ru(IMe4)2(P-P)HF (P-P = Ph2P(CH2)2PPh2 (dppe, cct-13), Ph2P(CH2)3PPh2 (dppp, cct-14), Ph2PCH2PPh2 (dppm, cct-15)), Ru(IEt2Me2)2(PPh3)2HF (cct-7; IEt2Me2 = 1,3-diethyl-4,5-dimethylimidazol-2-ylidene)), and Ru(IEt2Me2)2(dppe)2HF (cct-16) for comparison. Both cct-13 and cct-14 brought about near-quantitative conversion to C6FH5 in 24 h, in comparison to ca. 50% conversion with ttt-4 in 144 h.
- Cybulski, Mateusz K.,Nicholls, Jessica E.,Lowe, John P.,Mahon, Mary F.,Whittlesey, Michael K.
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p. 2308 - 2316
(2017/06/30)
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- Substitution of fluorine in M[C6F5BF3] with organolithium compounds: Distinctions between O- and N-nucleophiles
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Borates M[C6F5BF3] (M = K, Li, Bu4N) react with organolithium compounds, RLi (R = Me, Bu, Ph), in 1,2-dimethoxyethane or diglyme to give M[4-RC6F4BF3] and M[2-RC6Fsub
- Shabalin, Anton Yu.,Adonin, Nicolay Yu.,Bardin, Vadim V.
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supporting information
p. 703 - 713
(2017/06/21)
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- Reaction discovery using acetylene gas as the chemical feedstock accelerated by the stop-flow micro-tubing reactor system
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Acetylene gas has been applied as a feedstock under transition-metal catalysis and photo-redox conditions to produce important chemicals including terminal alkynes, fulvenes, and fluorinated styrene compounds. The reaction discovery process was accelerated through the use of stop-flow micro-tubing reactors. This reactor prototype was developed by joining elements from both continuous micro-flow and conventional batch reactors, which was convenient and effective for gas/liquid reaction screening. Notably, the developed transformations were either inefficient or unsuccessful in conventional batch reactors. Its success relies on the unique advantages provided by this stop-flow micro-tubing reactor system.
- Xue, Fei,Deng, Hongping,Xue, Chengwen,Mohamed, Dara Khairunnisa Binte,Tang, Karen Yuanting,Wu, Jie
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p. 3623 - 3627
(2017/07/11)
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- Competition of Nucleophilic Aromatic Substitution, σ-Bond Metathesis, and syn Hydrometalation in Titanium(III)-Catalyzed Hydrodefluorination of Arenes
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Several functionalized and non-functionalized perfluoroarenes were catalytically transformed into their para-hydrodefluorinated products by using catalytic amounts of titanocene difluoride and stoichiometric amounts diphenylsilane. Turnover numbers of up to 93 were observed. Solution density functional theory calculations at the M06-2X/TZ(PCM)//M06-2X/TZ(PCM) level of theory provided insight into the mechanism of TiIII-catalyzed aromatic hydrodefluorination. Two different substrate approaches, with a Ti–F interaction (pathway A) and without a Ti–F interaction (pathway B), are possible. Pathway A leads to a σ-bond metathesis transition state, whereas pathway B proceeds by means of a two-step mechanism through a syn-hydrometalation intermediate or through a Meisenheimer intermediate. Both pathways are competitive over a broad range of substrates.
- Krüger, Juliane,Leppkes, Jakob,Ehm, Christian,Lentz, Dieter
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p. 3062 - 3071
(2016/11/13)
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- “π-Hole?π” Interaction Promoted Photocatalytic Hydrodefluorination via Inner-Sphere Electron Transfer
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We describe a metal-free, photocatalytic hydrodefluorination (HDF) of polyfluoroarenes (FA) using pyrene-based photocatalysts (Py). The weak “π-hole?π” interaction between Py and FA promotes the electron transfer against unfavorable energetics (ΔGET up to 0.63 eV) and initiates the subsequent HDF. The steric hindrance of Py and FA largely dictates the HDF reaction rate, pointing to an inner-sphere electron transfer pathway. This work highlights the importance of the size and shape of the photocatalyst and the substrate in controlling the electron transfer mechanism and rates as well as the overall photocatalytic processes.
- Lu, Jingzhi,Khetrapal, Navneet S.,Johnson, Jacob A.,Zeng, Xiao Cheng,Zhang, Jian
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supporting information
p. 15805 - 15808
(2016/12/23)
-
- A decarboxylation multi-monofluoro-benzene multifluoro-benzoic acid by the method of preparation (by machine translation)
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This invention relates to a kind of the ammonia in the high-temperature liquid aqueous medium, in the copper-containing solid acid catalyst, reaction [...] multifluoro-benzoic acid by the method of preparation multi-monofluoro-benzene. The method disclosed by the present invention do not need to use organic solvent, cheap catalyst, has fast reaction speed, reaction time is short, the advantage of high product yield. (by machine translation)
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-
Paragraph 0067; 0068
(2017/03/25)
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- Substrate-Dependent Mechanistic Divergence in Decarboxylative Heck Reaction at Room Temperature
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We report herein a Pd(II)-catalyzed Heck-type coupling between arene carboxylic acids and alkenes at room temperature. Mechanistically, the reaction proceeds in two distinct pathways where electron-rich substrates undergo a palladium(II)-catalyzed decarboxylation and electron-deficient substrates proceed through silver(I)-assisted decarboxylation. Dimethyl sulfoxide (DMSO) or sulfide ligands have positive and negative roles in the reaction outcome, respectively. The present protocol is combined for the peptide modification under mild reaction conditions.
- Hossian, Asik,Bhunia, Samir Kumar,Jana, Ranjan
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p. 2521 - 2533
(2016/04/01)
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- Mechanical device for preparing bromopentafluorobenzene
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The invention discloses a mechanical device for preparing bromopentafluorobenzene. The mechanical device for preparing bromopentafluorobenzene belongs to the field of fine chemical production machinery. The mechanical device comprises a high-pressure reaction kettle (1), a chemical reaction kettle (2) and a reduced-pressure distiller (3). The mechanical device is characterized in that a pentafluorobenzoic acid inlet (4), a water inlet (5) and a waste liquid outlet (6) are arranged on the high-pressure reaction kettle (1); a first material slurry pump and pipeline (7) is arranged between the high-pressure reaction kettle (1) and the chemical reaction kettle (2); a bromine water inlet (8), a sodium sulfate aqueous solution inlet (9) and a waste liquid outlet (10) are arranged on the chemical reaction kettle (2); a second material slurry pump and pipeline (11) is arranged between the chemical reaction kettle (2) and the reduced-pressure distiller (3); a steam outlet (12) is arranged on the reduced-pressure distiller (3); and a final-product outlet (13) is arranged on the reduced-pressure distiller (3).
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-
Paragraph 0010-0012
(2017/03/23)
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- Hydrodefluorination of fluoroaromatics by isopropyl alcohol catalyzed by a ruthenium NHC complex. An unusual role of the carbene ligand
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The NHC (NHC = N-heterocyclic carbene) complex Cp*(IPr)RuH3 catalyzes hydrodefluorination of aromatic fluorides at 70 °C with isopropyl alcohol as the reducing reagent. The reaction is selective for aromatic fluorides, as almost negligible C(sp3)?F bond reduction takes place. The activity decreases from more to less fluorinated substrates, but polyaromatic monofluorides, such as 1-fluoronaphthalene and 6-fluoro-2-methylquinoline, can also be reduced in moderate to good yields. Kinetic studies are consistent with a mechanism based on elimination of NHC and reversible substrate coordination, followed by coordination of the alcohol.
- Mai, Van Hung,Nikonov, Georgii I.
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p. 7956 - 7961
(2018/05/23)
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