- Direct C?H Borylation of Arenes Catalyzed by Saturated Hydride-Boryl-Iridium-POP Complexes: Kinetic Analysis of the Elemental Steps
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The saturated trihydride IrH3{κ3-P,O,P-[xant(PiPr2)2]} (1; xant(PiPr2)2=9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) activates the B?H bond of two molecules of pinacolborane (HBpin) to give H2, the hydride-boryl derivatives IrH2(Bpin){κ3-P,O,P-[xant(PiPr2)2]} (2) and IrH(Bpin)2{κ3-P,O,P-[xant(PiPr2)2]} (3) in a sequential manner. Complex 3 activates a C?H bond of two molecules of benzene to form PhBpin and regenerates 2 and 1, also in a sequential manner. Thus, complexes 1, 2, and 3 define two cycles for the catalytic direct C?H borylation of arenes with HBpin, which have dihydride 2 as a common intermediate. C?H bond activation of the arenes is the rate-determining step of both cycles, as the C?H oxidative addition to 3 is faster than to 2. The results from a kinetic study of the reactions of 1 and 2 with HBpin support a cooperative function of the hydride ligands in the B?H bond activation. The addition of the boron atom of the borane to a hydride facilitates the coordination of the B?H bond through the formation of κ1- and κ2-dihydrideborate intermediates.
- Esteruelas, Miguel A.,Martínez, Antonio,Oliván, Montserrat,O?ate, Enrique
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supporting information
p. 12632 - 12644
(2020/09/09)
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- Cobalt-Catalyzed Regioselective Borylation of Arenes: N-Heterocyclic Silylene as an Electron Donor in the Metal-Mediated Activation of C?H Bonds
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C?H Borylation of arenes has been a subject of great interest recently because of its atom-economy and the wide applicability of borylated products in value-added synthesis. A new bis(silylene)cobalt(II) complex bearing a bis(N-heterocyclic silylene)-pyridine pincer ligand (SiNSi) has been synthesized and structurally characterized. It enabled the regioselective catalytic C?H borylation of pyridines, furans, and fluorinated arenes. Notably, it exhibited complementary regioselectivity for the borylation of fluorinated arenes compared to previously known catalytic systems, demonstrating that N-heterocyclic silylene donors have enormous potential in metal-catalyzed catalytic applications.
- Ren, Hailong,Zhou, Yu-Peng,Bai, Yunping,Cui, Chunming,Driess, Matthias
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supporting information
p. 5663 - 5667
(2017/04/28)
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- C-H borylation by platinum catalysis
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Herein, we describe the platinum-catalyzed borylation of aromatic C-H bonds. N-Heterocyclic carbene-ligated platinum catalysts are found to be efficient catalysts for the borylation of aromatic C(sp2)-H bonds when bis(pinacolato)diboron is used as the boron source. The most remarkable feature of these Pt catalysts is their lack of sensitivity towards the degree of steric hindrance around the C-H bonds undergoing the borylation reaction. These Pt catalysts allow for the synthesis of sterically congested 2,6-disubstituted phenylboronic esters, which are otherwise difficult to synthesize using existing C-H borylation methods. Furthermore, platinum catalysis allows for the site-selective borylation of the C-H bonds ortho to fluorine substituents in fluoroarene systems. Preliminary mechanistic studies and work towards the synthetic application of this platinum catalyzed C-H borylation process are described.
- Furukawa, Takayuki,Tobisu, Mamoru,Chatani, Naoto
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p. 332 - 342
(2017/05/09)
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- Preparing (Multi)Fluoroarenes as Building Blocks for Synthesis: Nickel-Catalyzed Borylation of Polyfluoroarenes via C-F Bond Cleavage
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The [Ni(IMes)2]-catalyzed transformation of fluoroarenes into arylboronic acid pinacol esters via C-F bond activation and transmetalation with bis(pinacolato)diboron (B2pin2) is reported. Various partially fluorinated arenes with different degrees of fluorination were converted into their corresponding boronate esters.
- Zhou, Jing,Kuntze-Fechner, Maximilian W.,Bertermann, Rüdiger,Paul, Ursula S. D.,Berthel, Johannes H. J.,Friedrich, Alexandra,Du, Zhenting,Marder, Todd B.,Radius, Udo
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supporting information
p. 5250 - 5253
(2016/05/19)
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- Miyaura Borylation and One-Pot Two-Step Homocoupling of Aryl Chlorides and Bromides under Solvent-Free Conditions
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Solvent-free protocols for Miyaura borylation and the one-pot, two-step homocoupling of aryl halides are reported for the first time. Bis(dibenzylideneacetone)palladium(0) [Pd(dba)2] is an optimal source of palladium for Miyaura borylation, while for one-pot two-step homocoupling palladium(II) acetate [Pd(OAc)2] gives highest yields. Aryl bromides are coupled most efficiently using the DPEphos ligand. Chlorides are coupled using XPhos. The developed protocols are robust, versatile and easily reproducible on a large scale.
- Dzhevakov, Pavel B.,Topchiy, Maxim A.,Zharkova, Daria A.,Morozov, Oleg S.,Asachenko, Andrey F.,Nechaev, Mikhail S.
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p. 977 - 983
(2016/04/05)
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- Fluorine-controlled C-H borylation of arenes catalyzed by a PSiN-pincer platinum complex
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An efficient, regioselective synthesis of fluorine-substituted arylboronic esters was achieved through fluorine-controlled C-H borylation of arenes with diboron catalyzed by a PSiN-platinum complex. The promising utility of the PSiN-platinum catalyst and its unique regioselectivity were demonstrated for the first time, which would complement the well-developed Ir-catalyzed C-H borylation.
- Takaya, Jun,Ito, Shisei,Nomoto, Hironori,Saito, Narumasa,Kirai, Naohiro,Iwasawa, Nobuharu
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supporting information
p. 17662 - 17665
(2015/12/18)
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- POP-rhodium-promoted C-H and B-H bond activation and C-B bond formation
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The square-planar monohydride complex RhH{xant(PiPr2)2} (1; xant(PiPr2)2 = 9,9-dimethyl-4,5-bis(diisopropylphosphino)xanthene) activates C-H bonds of arenes. Heating of benzene solutions of 1 at 80 °C affords RhPh{xant(PiPr2)2} (2). Under the same conditions, toluene gives Rh(m-tolyl){xant(PiPr2)2} (3a) and Rh(p-tolyl){xant(PiPr2)2} (3b) in a 78:22 molar ratio, whereas m-xylene leads to Rh(C6H3-3,5-Me2){xant(PiPr2)2} (4). At room temperature, fluorobenzene and 1,3-difluorobenzene generate Rh(C6H4-2-F){xant(PiPr2)2} (5) and Rh(C6H3-2,6-F2){xant(PiPr2)2} (6), respectively. Complex 1 also promotes the B-H bond activation of pinacolborane (HBpin) and catecholborane (HBcat). The reactions initially give the trans-dihydride derivatives RhH2(BR2){xant(PiPr2)2} (BR2 = Bpin (7), Bcat (8)), which lose H2 to afford the square-planar Rh(BR2){xant(PiPr2)2} (BR2 = Bpin (9), Bcat (10)). Complex 2 reacts with HBpin to regenerate 1 and to give Ph-Bpin. Similarly, complex 9 regenerates 1 and gives Ph-Bpin by reaction with benzene. In agreement with these transformations, complex 1 catalyzes the direct C-H borylation of arenes. The selectivity of the process appears to be governed by the kinetic of the C-H bond activations of the arenes. Benzylic borylation is not observed for methylbenzenes. The first X-ray structure of a square-planar rhodium-boryl complex is also reported.
- Esteruelas, Miguel A.,Oliván, Montserrat,Vélez, Andrea
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p. 1911 - 1924
(2015/06/08)
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- Regioselective electrophilic borylation of haloarenes
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Haloarenes undergo direct borylation using amine:BCl3:AlCl3 in the ratio of 1:1:2. After esterification the pinacol boronate esters are isolated in good yield with regioselectivity controlled by steric and electronic effects.
- Del Grosso, Alessandro,Ayuso Carrillo, Josue,Ingleson, Michael J.
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supporting information
p. 2878 - 2881
(2015/02/19)
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- C-H Functionalization at Sterically Congested Positions by the Platinum-Catalyzed Borylation of Arenes
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Despite significant progress in the area of C-H bond functionalization of arenes, no general method has been reported for the functionalization of C-H bonds at the sterically encumbered positions of simple arenes, such as mesitylene. Herein, we report the development of the first platinum-based catalyst for C-H borylation of arenes and heteroarenes. Notably, this method exhibited high tolerance toward steric hindrance and provided rapid access to a series of 2,6-disubstituted phenylboronic esters, valuable building blocks for further elaborations.
- Furukawa, Takayuki,Tobisu, Mamoru,Chatani, Naoto
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supporting information
p. 12211 - 12214
(2015/10/12)
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- Transition metal-free synthesis of pinacol arylboronate: Regioselective boronation of 1,3-disubstituted benzenes
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The regioselective synthesis of pinacol arylboronate has been achieved from 1,3-disubstituted benzene through directed ortho-metallation (DoM)-borylation sequence. A wide range of substituents and borylating reagents were investigated. In situ lithiation and subsequent boronation predominantly occurred at the ortho-position to afford the desired products in moderate yields. CSIRO 2014.
- Wang, Yan,Wang, Le,Chen, Ling-Yan,Bhadury, Pinaki S.,Sun, Zhihua
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p. 675 - 678
(2014/05/06)
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- Iridium complexes of N-heterocyclic carbenes in C-H borylation using energy efficient microwave technology: Influence of structure, ligand donor strength and counter ion on catalytic activity
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Bridged and unbridged N-heterocyclic carbene (NHC) ligands were metalated with [Ir(COD)Cl]2 to give iridium(i) mono- and biscarbene substituted catalysts [Ir(COD)NHC(Cl)] and [Ir(COD)(NHC)2][X] (X: I, PF 6, BF4, CF3COO, OTf). The prepared NHC-complexes were tested in the C-H borylation reaction of aromatic carbons with bis(pinacolato)diboron (B2pin2) and pinacolborane (HBpin). The use of microwave technology in this study not only facilitates a time efficient screening of a wide range of influences such as ligand σ-donor strength and structural motif as well as the effects of the complex counter ion, but also provides an energy efficient heating source. Catalyst 6TFA, which features a chelating NHC ligand, proved to be most effective catalyst and further investigations with this complex in the borylation of mono- and disubstituted benzene derivatives exploring chemo- and regioselectivity were undertaken. The Royal Society of Chemistry 2009.
- Rentzsch, Christoph F.,Tosh, Evangeline,Herrmann, Wolfgang A.,Kuehn, Fritz E.
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scheme or table
p. 1610 - 1617
(2010/05/18)
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- Sterically directed functionalization of aromatic C-H bonds: Selective borylation ortho to cyano groups in arenes and heterocycles
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Ir-catalyzed borylations of 4-substituted benzonitriles are described. In contrast to electrophilic aromatic substitutions and directed ortho metalations, C-H activation/borylation enables functionalization at the 2-position, adjacent to the cyano group, when the 4-subsitutent is larger than cyano. When an excess of borane reagent is used, diborylation can be achieved with a single regioisomer being formed in certain cases. Extension of sterically directed borylation to cyano-substituted, five- and six-membered ring heterocycles is also reported.
- Chotana, Ghayoor A.,Rak, Michael A.,Smith, Milton R.
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p. 10539 - 10544
(2007/10/03)
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