- Ruthenium-catalyzed regiospecific borylation of methyl C-H bonds
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We report the regiospecific, ruthenium-catalyzed borylation of saturated terminal C-H bonds. Alkylboronates were obtained in 78-98% yields. The borylations of alkanes, trialkylamines, protected alcohols, and fluoroalkanes occurred regiospecifically at the methyl group that is least sterically hindered. In contrast to most organometallic C-H activation, the reactions of alkanes occurred in higher yields than the reactions of arenes. Reactions were conducted that probed steric and electronic effects on the alkyl borylation. These reactions showed that the borylation occurred preferentially at the methyl group that is least sterically hindered and most electron-deficient. Ruthenium compounds containing boryl ligands were synthesized, and one was characterized by X-ray crystallography. One of these compounds contained a rare bridging boryl ligand and served as a catalyst precursor for the borylation of octane. Copyright
- Murphy, Jaclyn M.,Lawrence, Joshua D.,Kawamura, Kazumori,Incarvito, Christopher,Hartwig, John F.
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- Synthesis of catechol-, pinacol-, and neopentylglycolborane through the heterogeneous catalytic B-B hydrogenolysis of diboranes(4)
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A new synthetic approach to hydroboranes catechol-, pinacol-, and neopentylglycolborane has been developed. Starting from diboranes(4) B 2cat2, B2pin2, or B 2neop2, the respective boranes were obtained by heterogeneously catalyzed cleavage of the B-B bond in the respective diboranes with hydrogen. Group10 metals were found to be effective catalysts for this reaction. Copyright
- Braunschweig, Holger,Guethlein, Frank,Mailaender, Lisa,Marder, Todd B.
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- Metal-Organic Framework Stabilizes a Low-Coordinate Iridium Complex for Catalytic Methane Borylation
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Catalytic borylation has recently been suggested as a potential strategy to convert abundant methane to fine chemicals. However, synthetic utility of methane borylation necessitates significant improvement of catalytic activities over original phenanthroline-and diphosphine-Ir complexes. Herein, we report the use of metal-organic frameworks (MOFs) to stabilize low-coordinate Ir complexes for highly active methane borylation to afford the monoborylated product. The mono(phosphine)-Ir based MOF, Zr-P1-Ir, significantly outperformed other Ir catalysts in methane borylation to afford CH3Bpin with a turnover number of 127 at 110 °C. Density functional theory calculations indicated a significant reduction of activation barrier for the rate limiting oxidative addition of methane to the four-coordinate (P1)IrIII(Bpin)3 catalyst to form the six-coordinate (P1)IrV(Bpin)3(CH3)(H) intermediate, thus avoiding the formation of sterically encumbered seven-coordinate IrV intermediates as found in other Ir catalysts based on chelating phenanthroline, bipyridine, and diphosphine ligands. MOF thus stabilizes the homogeneously inaccessible, low-coordinate (P1)Ir(boryl)3 catalyst to provide a unique strategy to significantly lower the activation barrier for methane borylation. This MOF-based catalyst design holds promise in addressing challenging catalytic reactions involving highly inert substrates.
- Feng, Xuanyu,Song, Yang,Li, Zhe,Kaufmann, Michael,Pi, Yunhong,Chen, Justin S.,Xu, Ziwan,Li, Zhong,Wang, Cheng,Lin, Wenbin
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- A boron-nitrogen transborylation enabled, borane-catalysed reductive cyanation of enones
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Cyanation offers a simple method for the introduction of a nitrile group into organic molecules and an orthogonal route for the installation of a wide array of functional groups using simple transformations. Cyanation methods are dominated by transition metal catalysis and the use of hydrogen cyanide gas. Here, the electrophilic cyanation of enones was achieved using a main-group catalyst and a non-toxic, electrophilic cyanide source. This protocol was applied across a broad substrate scope including those containing reducible functional groups. Mechanistic studies indicated an amino-borane intermediate which underwent B-N transborylation (B-N/B-H exchange) to achieve catalytic turnover.
- Benn, Kieran,Nicholson, Kieran,Langer, Thomas,Thomas, Stephen P.
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supporting information
p. 9406 - 9409
(2021/09/22)
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- Hydrogen Evolution from Telescoped Miyaura Borylation and Suzuki Couplings Utilizing Diboron Reagents: Process Safety and Hazard Considerations
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The hazard assessment of a telescoped Miyaura borylation and Suzuki coupling reaction employing bis(pinacolato)diboron (BisPin), used in the developmental synthesis of an intermediate for abemaciclib, led to the observation of hydrogen being generated. Quantitative headspace GC and solution 11B NMR were used to show that the rapid decomposition of the excess BisPin from the borylation under the aqueous basic conditions of the Suzuki reaction was responsible for H2 generation. The moles of H2 observed were found equal to the BisPin excess, which is rationalized by mass balance and a stoichiometric reaction. The possible generation of the stoichiometric levels of H2 should be considered in hazard assessments of this class of reaction. Kinetic and process modeling was used to minimize the risk upon scale-up, and results for commercial manufacturing batches are presented, which showed good agreement with the lab scale data. Furthermore, the hydrogen evolution potentials of other common borylating agents including bisboronic acid (BBA) and pinacol borane were demonstrated.
- Borkar, Indrakant,Brewer, Alison Campbell,Buser, Jonas Y.,Campos, Odilon,Fleming, Jeffrey,Forst, Mindy B.,Hansen, Caoimhe,Humenik, Ashley,Jeffery, Stephen,Kokitkar, Prashant B.,Kolis, Stanley P.,Lambertus, Gordon R.,Martinelli, Joseph R.,McCartan, Ciaran,Merritt, Jeremy M.,Moursy, Hossam,Murphy, Donal,Murray, Michael M.,O'Donnell, Kevin,O'Sullivan, Rita,Richardson, Gary A.,Xia, Han
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- Regioselective Synthesis of α-Functional Stilbenes via Precise Control of Rapid cis- trans Isomerization in Flow
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The rapid cis-trans isomerization of α-anionic stilbene was regioselectively controlled by using flow microreactors, and its reaction with various electrophiles was conducted. The reaction time was precisely controlled within milliseconds to seconds at -50 °C to selectively give the cis- or trans-isomer in high yields. This synthetic method in flow was well-applied to synthesize precursors of commercial drug compound, (E)- and (Z)-tamoxifen with high regioselectivity and productivity.
- Lee, Hyune-Jea,Yonekura, Yuya,Kim, Nayoung,Yoshida, Jun-Ichi,Kim, Heejin
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supporting information
p. 2904 - 2910
(2021/05/05)
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- Synthesis of DBpin using Earth-abundant metal catalysis
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The synthesis of DBpin was achieved using (EtBIP)CoCl2 or (tBuPNN)FeCl2 as pre-catalysts activated with NaOtBu. (EtBIP)CoCl2 was used as a pre-catalyst for the hydrogen isotope exchange of HBpin with D2, and (tBuPNN)FeCl2 for deuterogenolysis of B2pin2. The one-pot, tandem hydrogenolysis-hydroboration/deuterogenolysis-deuteroboration reaction of terminal alkenes could be catalysed by (tBuPNN)FeCl2 to give alkyl boronic esters.
- Cummins, Andrew W. M.,Docherty, Jamie H.,Li, Shuyang,Muilu, Tommi,Thomas, Stephen P.,Willcox, Dominic R.
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supporting information
(2020/03/10)
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- A highly efficient cobalt-catalyzed deuterogenolysis of diboron: Synthesis of deuterated pinacolborane and vinylboronates
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Highly efficient hydrogenolysis and deuterogenolysis of diboron compounds have been realized by the use of a cobalt catalyst, affording TON up to 48201. Furthermore, a one-pot two-step procedure comprising sequential deuterogenolysis of diboron and deuteroboration of alkynes under the same cobalt catalyst has been developed for the efficient, atom-economical synthesis of deuterated vinylboronates with high deuterium incorporation and excellent regio- and stereoselectivity.
- Qiao, Lin,Zhang, Lei,Liu, Guixia,Huang, Zheng
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supporting information
p. 4138 - 4142
(2019/04/10)
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- Air-Stable α-Diimine Nickel Precatalysts for the Hydrogenation of Hindered, Unactivated Alkenes
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Treatment of a mixture of air-stable nickel(II) bis(octanoate), Ni(O2CC7H15)2, and α-diimine ligand, iPrDI or CyADI (iPrDI = [2,6-iPr2-C6H3N=C(CH3)]2, CyADI = [C6H11N=C(CH3)]2) with pinacolborane (HBPin) generated a highly active catalyst for the hydrogenation of hindered, essentially unfunctionalized alkenes. A range of tri- and tetrasubstituted alkenes was hydrogenated and a benchtop procedure for the hydrogenation of 1-phenyl-1-cyclohexene on a multigram scale was demonstrated and represents an advance in catalyst activity and scope for the nickel-catalyzed hydrogenation of this challenging class of alkenes. Deuteration of 1,2-dimethylindene with the in situ-generated nickel catalyst with iPrDI exclusively furnished the 1,2-syn-d2-dimethylindane. With cyclic trisubstituted alkenes, such as 1-methyl-indene and methylcyclohexene, deuteration with the in situ generated nickel catalyst under 4 atm of D2 produced multiple deuterated isotopologues of the alkanes, signaling chain running processes that are competitive with productive hydrogenation. Stoichiometric studies, titration, and deuterium labeling experiments identified that the borane reagent served the dual role of reducing nickel(II) bis(carboxylate) to the previously reported nickel hydride dimer [(iPrDI)NiH]2 and increasing the observed hydrogenation activity. Performing the catalyst activation procedure with D2 gas and HBPin generated both HD and DBPin, establishing that the borane is involved in H2 activation as judged by 1H and 11B nuclear magnetic resonance spectroscopies.
- Léonard, Nadia G.,Chirik, Paul J.
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p. 342 - 348
(2018/01/17)
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- Kinetic Resolution of Secondary Allyl Boronates and Their Application in the Synthesis of Homoallylic Amines
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Highly enantioenriched, chromatographically-stable secondary allyl boronates featuring a 1,1,2,2-tetraethyl-1,2-ethanediol fragment (Epin) were obtained by kinetic resolution of their racemic mixtures. The Epin group at boron considerably improved stability of allyl boronates allowing them to be readily isolated by chromatography on silica. The resolved reagents were applied in stereoselective synthesis of homoallylic amines with an internal double bond employing unprotected imines formed in situ from aldehydes and ammonia. The reactions proceeded with an excellent transfer of chirality.
- Villar, Laura,Orlov, Nikolai V.,Kondratyev, Nikolay S.,Uria, Uxue,Vicario, Jose L.,Malkov, Andrei V.
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supporting information
p. 16262 - 16265
(2018/10/20)
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- Mechanistic Studies of Copper-Catalyzed Asymmetric Hydroboration of Alkenes
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Mechanistic studies of the copper-catalyzed asymmetric hydroboration of vinylarenes and internal alkenes are reported. Catalytic systems with both DTBM-SEGPHOS and SEGPHOS as the ligands have been investigated. With DTBM-SEGPHOS as the ligand, the resting state of the catalyst, which is also a catalytic intermediate, for hydroboration of 4-fluorostyrene is a phenethylcopper(I) complex ligated by the bisphosphine. This complex was fully characterized by NMR spectroscopy and X-ray crystallography. The turnover-limiting step in the catalytic cycle for the reaction of vinylarenes is the borylation of this phenethylcopper complex with pinacolborane (HBpin) to form the boronate ester product and a copper hydride. Experiments showed that the borylation occurs with retention of configuration at the benzylic position. β-Hydrogen elimination and insertion of the alkene to reform this phenethylcopper complex is reversible in the absence of HBpin but is irreversible during the catalytic process because reaction with HBpin is faster than β-hydrogen elimination of the phenethylcopper complex. Studies on the hydroboration of a representative internal alkene, trans-3-hexenyl 2,4,6-trichlorobenzoate, which undergoes enantio- and regioselective addition of HBpin catalyzed by DTBM-SEGPHOS, KOtBu, and CuCl, also was conducted, and these studies revealed that a DTBM-SEGPHOS-ligated copper(I) dihydridoborate complex is the resting state of the catalyst in this case. The turnover-limiting step in the catalytic cycle for hydroboration of the internal alkene is insertion of the alkene into a copper(I) hydride formed by reversible dissociation of HBpin from the copper dihydridoborate species. With SEGPHOS as the ligand, a dimeric copper hydride was observed as the dominant species during the hydroboration of 4-fluorostyrene, and this complex is not catalytically competent. DFT calculations provide a view into the origins of regio- and enantioselectivity of the catalytic process and indicate that the charge on the copper-bound carbon and delocalization of charge onto the aryl ring control the rate of the alkene insertion and the regioselectivity of the catalytic reactions of vinylarenes.
- Xi, Yumeng,Hartwig, John F.
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supporting information
p. 12758 - 12772
(2017/09/25)
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- Preparation method of pinacolborane
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The invention relates to the field of chemical engineering synthesis, and discloses a preparation method of pinacolborane. The method is characterized in that pinacol and dichloroborane undergo a condensation reaction under an alkaline condition. Pinacolborane can be prepared at a high and stable yield through adopting the method, and the preparation method has the advantages of simplicity, easily available and cheap raw materials, great reduction of the production cost, and suitableness for industrial production.
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Paragraph 0026; 0039; 0040; 0041; 0042; 0043; 0044-0057
(2017/04/28)
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- Cobalt-Catalyzed C(sp2)-H Borylation: Mechanistic Insights Inspire Catalyst Design
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A comprehensive study into the mechanism of bis(phosphino)pyridine (PNP) cobalt-catalyzed C-H borylation of 2,6-lutidine using B2Pin2 (Pin = pinacolate) has been conducted. The experimentally observed rate law, deuterium kinetic isotope effects, and identification of the catalyst resting state support turnover limiting C-H activation from a fully characterized cobalt(I) boryl intermediate. Monitoring the catalytic reaction as a function of time revealed that borylation of the 4-position of the pincer in the cobalt catalyst was faster than arene borylation. Cyclic voltammetry established the electron withdrawing influence of 4-BPin, which slows the rate of C-H oxidative addition and hence overall catalytic turnover. This mechanistic insight inspired the next generation of 4-substituted PNP cobalt catalysts with electron donating and sterically blocking methyl and pyrrolidinyl substituents that exhibited increased activity for the C-H borylation of unactivated arenes. The rationally designed catalysts promote effective turnover with stoichiometric quantities of arene substrate and B2Pin2. Kinetic studies on the improved catalyst, 4-(H)2BPin, established a change in turnover limiting step from C-H oxidative addition to C-B reductive elimination. The iridium congener of the optimized cobalt catalyst, 6-(H)2BPin, was prepared and crystallographically characterized and proved inactive for C-H borylation, a result of the high kinetic barrier for reductive elimination from octahedral Ir(III) complexes.
- Obligacion, Jennifer V.,Semproni, Scott P.,Pappas, Iraklis,Chirik, Paul J.
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supporting information
p. 10645 - 10653
(2016/09/04)
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- A process for preparing a diboron ester (by machine translation)
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The invention discloses a process for preparing a diboron ester. Borane complexes and corresponding diol reaction and produce corresponding mellow borane, the iron then took place in the presence of catalyst to self-coupling forming a diboron ester. Short synthesis steps of the method, high safety, mild reaction conditions, suitable for many kinds of a diboron ester synthesis. (by machine translation)
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Paragraph 0013
(2016/12/16)
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- [3,3]-Sigmatropic rearrangement/allylboration/cyclization sequence: Enantioenriched seven-membered-ring carbamates and ring contraction to pyrrolidines
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The combination of in situ generated α-isocyanato allylboronic esters and aldehydes afforded seven-membered-ring enecarbamates with high levels of diastereo- and enantiocontrol. They were easily converted into diversely substituted 1,3-oxazepan-2-ones. An unprecedented rearrangement of 5-acetoxy-7-aryl or styryl derivatives led to tetrasubstituted pyrrolidines. A computational study provides evidence on the feasibility of the proposed mechanism of this unusual ring contraction. Honey I shrunk the rings: A new protocol for the diastereo- and enantiocontrolled synthesis of seven-membered-ring ene carbamates is described. These compounds were easily converted into diversely substituted 1,3-oxazepan-2-ones. Tetrasubstituted pyrrolidines were obtained by an unprecedented ring contraction rearrangement of a 5-acetoxy derivative in the presence of trifluoroboron etherate.
- Macé, Aurélie,Touchet, Sabrina,Andres, Patricia,Cossío, Fernando,Dorcet, Vincent,Carreaux, Fran?ois,Carboni, Bertrand
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supporting information
p. 1025 - 1029
(2016/01/20)
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- Adaptability of the SiNN Pincer Ligand in Iridium and Rhodium Complexes Relevant to Borylation Catalysis
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A comparison of Rh and Ir complexes of the SiNN ligand (combining Si-H, amido, and quinoline donors) reveals its great degree of adaptability. The amido donor can function as a boryl group acceptor, and the Si-H/metal interaction is highly variable. In contrast to Ir analogues, complexes of Rh do not catalyze dehydrogenative borylation of terminal alkynes but do act as modest benzene borylation catalysts.
- Lee, Chun-I,Hirscher, Nathanael A.,Zhou, Jia,Bhuvanesh, Nattamai,Ozerov, Oleg V.
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supporting information
p. 3099 - 3102
(2016/01/15)
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- Reversible Borylene Formation from Ring Opening of Pinacolborane and Other Intermediates Generated from Five-Coordinate Tris-Boryl Complexes: Implications for Catalytic C-H Borylation
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Catalytic C-H borylation using the five-coordinate tris-boryl complex (dippe)Ir(Bpin)3 (5a, dippe = 1,2-bis(diisopropylphosphino)ethane) has been examined using 31P{1H} and 1H NMR spectroscopy. Compound 5a was shown to react rapidly and reversibly with HBpin to generate a six-coordinate borylene complex, (dippe)Ir(H)(Bpin)2(BOCMe2CMe2OBpin) (6), whose structure was confirmed by X-ray crystallography. Under catalytic conditions, the H2 generated from C-H borylation converted compound 6 to a series of intermediates. The first is tentatively assigned from 31P{1H} and 1H NMR spectra as (dippe)Ir(H2B3pin3) (7), which is the product of formal H2 addition to compound 5a. As catalysis progressed, compound 7 was converted to a new species with the formula (dippe)Ir(H3B2pin2) (8), which arose from H2 addition to compound 7 with loss of HBpin. Compound 8 was characterized by 31P{1H} and 1H NMR spectroscopy, and its structure was confirmed by X-ray crystallography, where two molecules with different ligand orientations were found in the unit cell. DFT calculations support the formulation of compound 8 as an IrIII agostic borane complex, (dippe)IrH2(Bpin)(η2-HBpin). Compound 8 was gradually converted to (dippe)Ir(H4Bpin) (9), which was characterized by 31P{1H} and 1H NMR spectroscopy and X-ray crystallography. DFT calculations favor its formulation as an agostic borane complex of IrIII with the formula (dippe)IrH3(η2-HBpin). Compound 9 reacted further with H2 to afford the dimeric structure [(dippe)IrH2(μ2-H)]2 (10), which was characterized by 1H NMR and X-ray crystallography. Compounds 7-10 are in equilibrium when H2 and HBpin are present.
- Ghaffari, Behnaz,Vanchura, Britt A.,Chotana, Ghayoor A.,Staples, Richard J.,Holmes, Daniel,Maleczka, Robert E.,Smith, Milton R.
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p. 4732 - 4740
(2015/10/28)
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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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- Iridium-catalysed borylation of sterically hindered C(sp3)-H bonds: Remarkable rate acceleration by a catalytic amount of potassium tert-butoxide
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The C(sp3)-H bonds located on the methyl groups of an isopropyl group participate in iridium-catalysed C-H borylation with bis(pinacolato) diboron via a significant rate acceleration caused by a catalytic amount of t-BuOK. the Partner Organisations 2014.
- Ohmura, Toshimichi,Torigoe, Takeru,Suginome, Michinori
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supporting information
p. 6333 - 6336
(2014/06/09)
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- Threefold cross-linked polystyrene-triphenylphosphane hybrids: Mono-P-ligating behavior and catalytic applications for aryl chloride cross-coupling and C(sp3)-H borylation
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Covalently bound polystyrene-phosphane hybrids were prepared by a method based on radical emulsion polymerization of styrenes in the presence of a tris(p-vinylphenyl)phosphane cross-linker. These hybrids favor mono-P-ligation to transition-metal complexes and are useful for challenging catalysis, such as Pd-catalyzed C-C/C-N couplings with unactivated chloroarenes and Ir- or Rh-catalyzed C(sp3)-H borylations. Copyright
- Iwai, Tomohiro,Harada, Tomoya,Hara, Kenji,Sawamura, Masaya
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supporting information
p. 12322 - 12326
(2013/12/04)
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- Tandem reactions involving 1-silyl-3-boryl-2-alkenes. New access to (Z)-1-fluoro-1-alkenes, allyl fluorides, and diversely α-substituted allylboronates
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The reactions of 1-silyl-3-boryl-2-alkenes with various electrophilic reagents (Selectfluor, N-halosuccinimides, benzhydryl, and propargylic alcohols in the presence of a Lewis acid, N-alkoxycarbonyliminium ion) have been investigated as new routes to α-substituted allylboronates. Further functional transformations, including allylboration, Suzuki coupling, protodeboronation, and cycloisomerization, have been carried out to illustrate the synthetic potential of these γ-borylallylsilanes.
- MacE, Aurelie,Tripoteau, Fabien,Zhao, Qian,Gayon, Eric,Vrancken, Emmanuel,Campagne, Jean-Marc,Carboni, Bertrand
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supporting information
p. 906 - 909
(2013/03/28)
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- Highly stereoselective synthesis of z-homoallylic alcohols by kinetic resolution of racemic secondary allyl boronates
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α to Z: Racemic α-chiral allyl boronates, which are readily synthesized from the respective primary allyl halides, undergo a highly efficient kinetic resolution in a face- and Z-selective allylation of aldehydes catalyzed by the chiral Bronsted acid (R)-TRIP (see scheme; Epin=tetraethylethylene glycol). Copyright
- Incerti-Pradillos, Celia A.,Kabeshov, Mikhail A.,Malkov, Andrei V.
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supporting information
p. 5338 - 5341
(2013/06/05)
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- 3-Chloro-1-lithiopropene, a functional organolithium reagent, and its reactions with alkylboronates to give 3-alkylprop-1-en-3-ols
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The reagent 3-chloro-1-lithiopropene (4) can be generated by treating 1-bromo-3-chloropropene with t-BuLi. It is unstable but if generated at low temperature in the presence of alkylboronic esters, such as 3, is trapped in situ to give rearrangement products 2, which on oxidation give 3-alkylprop-1-en-3-ols in good yields. The reaction works for primary, secondary, benzylic, and even tertiary alkylboronic esters, providing allylic alcohols bearing almost any alkyl group available using organoborane chemistry and incorporating all features of such groups.
- Smith, Keith,Elliott, Mark C.,Jones, D. Heulyn
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p. 9526 - 9531
(2013/10/08)
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- Iridium-catalyzed borylation of secondary C-H bonds in cyclic ethers
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The borylation of secondary C-H bonds, specifically secondary C-H bonds of cyclic ethers, with a catalyst generated from tetramethylphenanthroline and an iridium precursor is reported. This borylation occurs with unique selectivity for the C-H bonds located β to the oxygen atoms over the weaker C-H bonds located α to oxygen atoms. Mechanistic studies imply that the C-H bond cleavage occurs directly at the β position rather than at the α position followed by isomerization of a reaction intermediate.
- Liskey, Carl W.,Hartwig, John F.
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p. 12422 - 12425
(2012/09/05)
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- Rh-catalyzed borylation of N-adjacent C(sp3)-H bonds with a silica-supported triarylphosphine ligand
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Direct C(sp3)-H borylation of amides, ureas, and 2-aminopyridine derivatives at the position α to the N atom, which gives the corresponding α-aminoalkylboronates, has been achieved with a heterogeneous catalyst system consisting of [Rh(OMe)(cod)]2 and a silica-supported triarylphosphine ligand (Silica-TRIP) that features an immobilized triptycene-type cage structure with a bridgehead P atom. The reaction occurs not only at terminal C-H bonds but also at internal secondary C-H bonds under mild reaction conditions (25-100 °C, 0.1-0.5 mol % Rh).
- Kawamorita, Soichiro,Miyazaki, Tatsuya,Iwai, Tomohiro,Ohmiya, Hirohisa,Sawamura, Masaya
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supporting information; experimental part
p. 12924 - 12927
(2012/10/08)
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- Rh-catalyzed ortho -selective C-H borylation of N-functionalized arenes with silica-supported bridgehead monophosphine ligands
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Supported phosphine-Rh systems, prepared in situ from silica-supported bridgehead monophosphines and [Rh(OH)(cod)]2, have enabled ortho-selective C-H borylation for a range of arenes containing nitrogen-based directing groups. The regioselectivity was excellent with various N-directing groups, including saturated and unsaturated N-heterocycles, tert-aminoalkyl groups, and imine-type C-N double bonds. The reaction showed significant tolerance toward steric repulsion around the reacting C-H bond. This Rh catalysis complements the Ir-catalyzed ortho-borylation, which is effective for arenes with oxygen-based directing groups.
- Kawamorita, Soichiro,Miyazaki, Tatsuya,Ohmiya, Hirohisa,Iwai, Tomohiro,Sawamura, Masaya
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p. 19310 - 19313
(2012/01/15)
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- PROCESS FOR THE PREPARATION OF SUBSTITUTED PHENYLALANINES
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Intermediates and synthetic processes for the preparation of substituted phenylalanine-based compounds are disclosed.
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Page/Page column 4
(2011/06/19)
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- A highly reactive rhodium(I)-boryl complex as a useful tool for C-H bond activation and catalytic C-F bond borylation
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Chemical Equation Presentation C-F bond borylation: A 16-electron rhodium (1)-boryl complex was synthesized by borylation of a rhodium (1)-fluorine complex. The former reacts with benzene or 2,3,5,6-tetrafluoropyridine by C-H activation. A catalytic C-F borylation reaction of pentafluoropyridine was also developed, which uses [Rh(Bpin) (PEt3)3] as a catalyst and Me3SiSiMe3 as a solvent. pin = pinacol.
- Teltewskoi, Michael,Panetier, Julien A.,Macgregor, Stuart A.,Braun, Thomas
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supporting information; experimental part
p. 3947 - 3951
(2010/10/01)
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- Palladium-catalyzed borylation of l-tyrosine triflate derivative with pinacolborane: practical route to 4-borono-l-phenylalanine (l-BPA) derivatives
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Efficient palladium-catalyzed borylation of protected l-tyrosine triflate with pinacolborane was achieved despite previous reports to the contrary. In addition to the use of an inexpensive boron source, the reaction was carried out in the presence of only 0.5 mol % palladium catalyst. Furthermore, the borylation can be performed using pinacolborane prepared in situ from pinacol and borane-diethylaniline complex. This represents a practical entry to 4-borono-l-phenylalanine (l-BPA) derivatives.
- Iimura, Shinya,Wu, Wenxue
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supporting information; experimental part
p. 1353 - 1355
(2010/05/03)
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- "One-pot" tandem C - H borylation/1,4-conjugate addition/reduction sequence
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A microwave-assisted, one-pot, iridium-catalyzed aromatic C - H borylation/rhodium-catalyzed 1,4-conjugate addition sequence provides a highly robust protocol suitable for high-throughput array synthesis. Selective formation of either β-aryl-substituted ketones or the corresponding alcohols can be achieved in good overall yields by simple variation of the reaction conditions.
- Tajuddin, Hazmi,Shukla, Lena,Maxwell, Aoife C.,Marder, Todd B.,Steel, Patrick G.
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supporting information; experimental part
p. 5700 - 5703
(2011/03/19)
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- SN2′ boron-mediated Mitsunobu reactions - A new one-pot three-component synthesis of substituted enamides and enol benzoates
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The conversion of (3-hydroxy-1-propen-1-yl)boronates to substituted enamides and enol benzoates is readily achieved in a one-pot procedure consisting of a regiocontrolled Mitsunobu reaction with convenient nucleophiles, followed by allylboration of aldehydes. Wiley-VCH Verlag GmbH & Co. KGaA, 2009.
- Berree, Fabienne,Gernigon, Nicolas,Hercouet, Alain,Chia, Hui Lin,Carboni, Bertrand
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supporting information; experimental part
p. 329 - 333
(2009/07/04)
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- A convenient catalyst for aqueous and protein Suzuki-Miyaura cross-coupling
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(Figure Presented) A phosphine-free palladium catalyst for aqueous Suzuki-Miyaura cross-coupling is presented. The catalyst is active enough to mediate hindered, ortho-substituted biaryl couplings but mild enough for use on peptides and proteins. The Suzuki-Miyaura couplings on protein substrates are the first to proceed in useful conversions. Notably, hydrophobic aryl and vinyl groups can be transferred to the protein surface without the aid of organic solvent since the aryl- and vinylboronic acids used in the coupling are water-soluble as borate salts. The convenience and activity of this catalyst prompts use in both general synthesis and bioconjugation.
- Chalker, Justin M.,Wood, Charlotte S. C.,Davis, Benjamin G.
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supporting information; experimental part
p. 16346 - 16347
(2010/01/29)
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- PROCESSES FOR THE PREPARATION OF BIPHENYL COMPOUNDS
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The invention concerns processes for the synthesis of a compound of the formula: wherein: R1 and R2 are each, independently, C1-C12 alkyl, CO2R3, OR4, R5(OR6), or C6-C18 aiyl; R3 -R6 are each, independently, C1-C12 alkyl or C6-C12 aryl; and n and m are each, independently, O or an integer from 1-5; said process comprising: — contacting a compound of the formula H0-R7-0H with BH3 and a compound of the formula in the presence of a nickel-containing catalyst to produce a first product, where R7 is a C2-C12 hydrocarbon group and X is a halogen, OMs or OTs; — contacting the first product in situ with a compound of the formula: in the presence of a nickel-containing catalyst to produce a compound of formula I, where Z is a halogen.
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Page/Page column 15; 16
(2010/01/29)
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- Practical synthesis of pinacolborane for one-pot synthesis of unsymmetrical biaryls via aromatic C-H borylation-cross-coupling sequence
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A method for practical preparation of pinacolborane from borane-diethylaniline and pinacol was newly developed. Aromatic C-H borylation of arenes with pinacolborane or bis(pinacolato)diboron catalyzed by 1/2[Ir(OMe)(COD)]2-(4,4′-di-tert-butyl-2,2′-bipyridine) at 25 °C in hexane to give arylboronic esters was directly followed by cross-coupling with aromatic bromides at 60 °C in the presence of PdCl2(dppf) (3.0 mol %) and K3PO4 in DMF. This one-pot, two-step procedure provided a variety of unsymmetrical biaryls in high yields.
- Kikuchi, Takao,Nobuta, Yusuke,Umeda, Junko,Yamamoto, Yasunori,Ishiyama, Tatsuo,Miyaura, Norio
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p. 4967 - 4971
(2008/09/21)
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- Sequential Ni-catalyzed borylation and cross-coupling of aryl halides via in situ prepared neopentylglycolborane
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(Chemical Equation Presented) A procedure for NiCl2(dppp)- catalyzed pinacolborylation and neopentylglycolborylation that utilizes in situ prepared inexpensive pinacolborane and neopentylglycolborane is reported. The scope of this reaction was demonstrated with a variety of aryl bromides and iodides. The resulting aryl neopentylglycolboronic esters undergo a NiCl 2(dppe)-catalyzed cross-coupling with aryl halides, resulting in an extremely efficient and cost-effective method for the synthesis of functional biaryls, dendritic building blocks, and other complex architectures.
- Rosen, Brad M.,Huang, Chenghong,Percec, Virgil
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supporting information; experimental part
p. 2597 - 2600
(2009/05/27)
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- Six- and eightfold palladium-catalyzed gross-coupling reactions of hexa- and octabromoarenes
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Palladium-catalyzed sixfold coupling of hexabromobenzene (20) with a variety of alkenylboronates and alkenylstannanes provided hexaalkenylbenzenes 1 in up to 73% and 16 to 41% yields, respectively. In some cases pentaalkenylbenzenes 21 were isolated as the main products (up to 75%). Some functionally substituted hexaalkenylbenzene derivatives containing oxygen or sulfur atoms in each of their six arms have also been prepared (16 to 24% yield). The sixfold coupling of the less sterically encumbered 2, 3, 6, 7, 10, 11-hexabromotriphenylene (24) gave the desired hexakis(3,3-dimethyl-1-butenyl) triphenylene (25) in 93% yield. The first successful cross-coupling reaction of octabromonaphthalene (26) gave octakis-(3,3-dimethyl-1-butenyl)naphthalene (27) in 21% yield. Crystal structure analyses disclose that, depending on the nature of the substituents, the six arms are positioned either all on the same side of the central benzene ring as in 1a and 1i, making them nicely cup-shaped molecules, or alternatingly above and below the central plane las in 1h and 23. In 27, the four arms at C-1, 4, 6, 7 are down, while the others are up, or vice versa. Upon catalytic hydrogenation, 1a yielded 89% of hexakis(tert-butylethyl)benzene (23). Some efficient accesses to alkynes with sterically demanding substituents are also described. Elimination of phosphoric acid from the enol phosphate derived from the corresponding methyl ketones gave 1-ethynyladamantane (3b, 62% yield), 1-ethynyl-1-methylcyclohexane (3c, 85%) and 3,3-dimethylpentyne (3e, 65%). 1-(Trimethylsilyl)ethynylcyclopropane (7) was used to prepare 1-ethynyl-1-methylcyclopropane (3d) (two steps, 64% overall yield). The functionally substituted alkynes 3 f-h were synthesized in multistep sequences starting from the propargyl chloride 11, which was prepared in high yields from the dimethylpropargyl alcohol 10 (94%). The alkenylstannanes 19 were prepared by hydrostannation of the corresponding alkynes in moderate to high yields (42-97%), and the alkenylboronates 2 and 4 by hydroboration with catecholborane (27-96% yield) or pinacolborane (26-69% yield).
- Stulgies, Balder,Prinz, Peter,Magull, Joerg,Rauch, Karsten,Meindl, Kathrin,Ruehl, Stephan,De Meijere, Armin
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p. 308 - 320
(2007/10/03)
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- Mechanism of the mild functionalization of arenes by diboron reagents catalyzed by iridium complexes. Intermediacy and chemistry of bipyridine-ligated iridium trisboryl complexes
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This paper describes mechanistic studies on the functionalization of arenes with the diboron reagent B2pin2 (bis-pinacolato diborane(4)) catalyzed by the combination of 4,4′-di-tert-butylbipyridine (dtbpy) and olefin-ligated iridium halide or olefin-ligated iridium alkoxide complexes. This work identifies the catalyst resting state as [Ir(dtbpy)(COE)(Bpin)3] (COE = cyclooctene, Bpin = 4,4,5,5-tetramethyl-1,3,2-dioxaborolanyl). [Ir(dtbpy)(COE)(Bpin)3] was prepared by independent synthesis in high yield from [Ir(COD)(OMe)] 2, dtbpy, COE, and HBpin. This complex is formed in low yield from [Ir(COD)(OMe)]2, dtbpy, COE, and B2pin2. Kinetic studies show that this complex reacts with arenes after reversible dissociation of COE. An alternative mechanism in which the arene reacts with the Ir(I) complex [Ir(dtbpy)Bpin] after dissociation of COE and reductive elimination of B2pin2 does not occur to a measurable extent. The reaction of [Ir(dtbpy)(COE)(Bpin)3] with arenes and the catalytic reaction of B2pin2 with arenes catalyzed by [Ir(COD)(OMe)]2 and dtbpy occur faster with electron-poor arenes than with electron-rich arenes. However, both the stoichiometric and catalytic reactions also occur faster with the electron-rich heteroarenes thiophene and furan than with arenes, perhaps because η2-heteroarene complexes are more stable than the η2-arene complexes and the η2-heteroarene or arene complexes are intermediates that precede oxidative addition. Kinetic studies on the catalytic reaction show that [Ir(dtbpy)(COE)(Bpin)3] enters the catalytic cycle by dissociation of COE, and a comparison of the kinetic isotope effects of the catalytic and stoichiometric reactions shows that the reactive intermediate [Ir(dtbpy)(Bpin)3] cleaves the arene C-H bond. The barriers for ligand exchange and C-H activation allow an experimental assessment of several conclusions drawn from computational work. Most generally, our results corroborate the conclusion that C-H bond cleavage is turnover-limiting, but the experimental barrier for this bond cleavage is much lower than the calculated barrier.
- Boller, Timothy M.,Murphy, Jaclyn M.,Hapke, Marko,Ishiyama, Tatsuo,Miyaura, Norio,Hartwig, John F.
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p. 14263 - 14278
(2007/10/03)
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- Rhodium boryl complexes in the catalytic, terminal functionalization of alkanes
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A series of studies have been conducted by experimental and theoretical methods on the synthesis, structures, and reactions of Cp*Rh boryl complexes that are likely intermediates in the rhodium-catalyzed regioselective, terminal functionalization of alkanes. The photochemical reaction of Cp*Rh(η6-C6Me6) with pinacolborane (HBpin) generates the bisboryl complex Cp*Rh(H)2(Bpin) 2 (2), which reacts with neat HBpin to generate Cp*Rh(H)(Bpin) 3 (3). X-ray diffraction, density functional theory (DFT) calculations, and NMR spectroscopy suggest a weak, but measurable, B-H bonding interaction. Both 2 and 3 dissociate HBpin and coordinate PEt3 or P(p-Tol)3 to generate the conventional rhodium(III) species Cp*Rh(PEt3)(H)(Bpin) (4) and Cp*Rh[P(p-tol) 3](Bpin)2 (5). Compounds 2 and 3 also react with alkanes and arenes to form alkyl- and arylboronate esters at temperatures similar to or below those of the catalytic borylation of alkanes and arenes. Further, these compounds were observed directly in catalytic reactions. The enthalpies and free energies for generation of the 16-electron intermediate and for the C-H bond cleavage and B-C bond formation have been calculated with DFT. These results strongly suggest that the C-H bond cleavage process occurs by a metal-assisted σ-bond metathesis mechanism to generate a borane complex that isomerizes if necessary to place the alkyl group cis to the boryl group. This complex with cis boryl and alkyl groups then undergoes B-C bond formation by a second σ-bond metathesis to generate the final functionalized product.
- Hartwig, John F.,Cook, Kevin S.,Hapke, Marko,Incarvito, Christopher D.,Fan, Yubo,Webster, Charles Edwin,Hall, Michael B.
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p. 2538 - 2552
(2007/10/03)
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- Regiospecific functionalization of methyl C-H bonds of alkyl groups in Reagents with heteroatom functionality
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We report the regiospecific, rhodium-catalyzed borylation of saturated terminal C-H bonds in molecules with existing functionality. Moderate to good yields were obtained with the organic substrate in excess and as limiting reagent. The borylations of trialkylamines, protected alcohols, protected ketones, and fluoroalkanes occurred regiospecifically at the methyl group that is least sterically hindered. Reactions were also conducted that probed electronic effects on the alkyl borylation. These reactions showed that the borylation occurred preferentially at the methyl group that is most electron-deficient. Methods to conduct tandem borylation of C-H bonds and conversion of the resulting boronate esters to alcohols, alkylarenes, and alkyltrifluoroborates were also developed. Copyright
- Lawrence, Joshua D.,Takahashi, Makoto,Bae, Chulsung,Hartwig, John F.
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p. 15334 - 15335
(2007/10/03)
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- Hydroboronation process
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The invention relates to processes for the synthesis of aryl or alkene borates which comprises reacting: (i) an olefinic compound having a halogen or halogen-like substituent in a vinylic substitution position, or (ii) an aromatic ring having a halogen or halogen-like substituent in a ring substitution position, with a disubstituted monohydroborane in the presence of a Group 8-11 metal catalyst. The invention also relates to the use of these borates in coupling reactions. The invention further relates to certain disubstituted monohydroboranes and aryl or alkene borates.
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Page column 39
(2010/02/05)
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- Rhodium silyl boryl hydride complexes: Comparison of bonding and the rates of elimination of borane, silane, and dihydrogen
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Spoilt for choice: a silane, dihydrogen, borane, or hydridoborate complex? The silyl boryl hydride complex [Cp*Rh(H2) (Et 3Si)(Bpin)] (Bpin = (pinacolato) boryl) could adopt any of these structures, but it appears to contain stronger B-H bonding than Si-H or H-H bonding and undergoes elimination of pinacolborane faster than of silane or hydrogen (see scheme). The bonding situation is studied by experimental and theoretical methods.
- Cook, Kevin S.,Incarvito, Christopher D.,Webster, Charles Edwin,Fan, Yubo,Hall, Michael B.,Hartwig, John F.
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p. 5474 - 5477
(2007/10/03)
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- Sulfonamide derivatives
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The present invention provides certain sulfonamide derivatives useful for potentiating glutamate receptor function in a patient and therefore, useful for treating a wide variety of conditions, such as psychiatric and neurological disorders.
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- Pinacolborane
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(A) Compound 1 can perform hydroboration of alkynes, catalyzed by transition metals (Rh, Ni), to give vinylboronates in essentially quantitative yield. The regioselectivity of hydroboration of allenes under Pd(O) catalysis can be fully controlled (to give 2, 3, or 4) by varying the phosphine ligands.
- Song
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p. 1210 - 1210
(2007/10/03)
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- Catalytic, regiospecific end-functionalization of alkanes: Rhenium-catalyzed borylation under photochemical conditions
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Approaching a Holy Grail? A regioselective functionalization of alkanes occurs with commercially available rhenium catalysts and borane reagents under photochemical conditions [Eq.(1)]. Mechanistic studies indicate that the regioselectivity results from a direct thermal reaction of a photochemically generated 16- electron boryl complex with alkane.
- Chen, Huiyuan,Hartwig, John F.
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p. 3391 - 3393
(2007/10/03)
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