- A new enabling technology for convenient laboratory scale continuous flow processing at low temperatures
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A new machine for conducting continuous flow processes at low temperatures on a laboratory scale is reported. The use of this cryogenic flow reactor has been demonstrated by the preparation of a variety of (hetero)aromatic boronic acids and esters via lit
- Browne, Duncan L.,Baumann, Marcus,Harji, Bashir H.,Baxendale, Ian R.,Ley, Steven V.
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- Preparation and reactions of 4-iodobutyl pinacolborate. Synthesis of substituted alkyl and aryl pinacolboronates via 4-iodobutyl pinacolborate utilizing tetrahydrofuran as the leaving group
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Iodine reacts with 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (HBpin), under ambient reaction conditions in THF, to form the iodoalkylborate species 2-(4-iodobutoxy)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (4-IboxBpin). Apparently, one-half equivalent of I2 reacts with HBpin to form IBpin in pentanes, which in turn cleaves THF to form the 4-IboxBpin. Alkyl and aryl Grignard reagents, prepared under Barbier conditions, then react with 4-IboxBpin to form the corresponding alkyl and aryl pinacolboronates while reforming and liberating THF as the leaving group.
- Murphy, Chris L.,Hall, Aaron,Roberts, Emily J.,Ryan, Matthew D.,Clary, Jacob W.,Singaram, Bakthan
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- Investigation of a lithium-halogen exchange flow process for the preparation of boronates by using a cryo-flow reactor
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Conducting low-temperature organometallic reactions under continuous flow conditions offers the potential to more accurately control exotherms and thus provide more reproducible and scalable processes. Herein, progress towards this goal with regards to the lithium-halogen exchange/borylation reaction is reported. In addition to improving the scope of substrates available on a research scale, methods to improve reaction profiles and expedite purification of the products are also described. On moving to a continuous system, thermocouple measurements have been used to track exotherms and provide a level of safety for continuous processing of organometallic reagents. The use of an in-line continuous liquid-liquid separation device to circumvent labour intensive downstream off-line processing is also reported. A cool setup: A small footprint, modular setup based around a cryo-flow reactor is reported for the preparation of gram quantities of boronic esters. With minimum alteration, including the addition of a data logger with thermocouples and a liquid-liquid separator, the same equipment can be used to scale the process, inclusive of an in-line extraction. Copyright
- Newby, James A.,Huck, Lena,Blaylock, D. Wayne,Witt, Paul M.,Ley, Steven V.,Browne, Duncan L.
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- An opportunity for Mg-catalyzed grignard-type reactions: Direct coupling of benzylic halides with pinacolborane with 10 mol % of magnesium
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Mg in catalytic amounts as the only metal permits the reductive coupling between benzyl halides and pinacolborane. HBpin acts both as an electrophile and as a reducing agent to regenerate an organomagnesium species in situ. An hydride oxidation mechanism is proposed on the basis of DFT calculations.
- Pintaric, Christine,Olivero, Sandra,Gimbert, Yves,Chavant, Pierre Y.,Dunach, Elisabet
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- Pd II -Porphyrin Complexes - The First Use as Safer and Efficient Catalysts for Miyaura Borylation
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We have developed a simple and convenient procedure for the preparation of pinacol arylboronates from aryl/heteroaryl bromides and bis(pinacolato)diborane using a Pd II -porphyrin complex as a catalyst. Seven different Pd II -porphyrin complexes (Pd II -T m HPP, Pd II -T m CPP, Pd II -TPP, Pd II -TST p SPP, Pd II -T p CPP, Pd II -T p TP, and Pd II -T p AP) have been synthesized and investigated for their catalytic influence in the Miyaura borylation.
- Rao, Kanusu Umamaheswara,Venkateswarlu, Katta
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- Remote steric control for undirected meta-selective C-H activation of arenes
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Regioselective functionalization of arenes remains a challenging problem in organic synthesis. Steric interactions are often used to block sites adjacent to a given substituent, but they do not distinguish the remaining remote sites. We report a strategy
- Asako, Sobi,Ilies, Laurean,Jin, Yushu,Ramadoss, Boobalan
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p. 658 - 663
(2022/02/21)
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- Arene borylation through C–H activation using Cu3(BTC)2 as heterogeneous catalyst
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C–H borylation by diborane is an important process to access organoboron compounds. Noble metals, including Ir and Rh-based complexes either in the form of homogeneous or heterogeneous catalysts, have been reported to promote arene C–H borylation. Recently, metal organic frameworks (MOFs) having Ir and Co as active sites have been used as catalysts, but they require co-catalysts. In the present study, commercially available Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) MOF is reported as an effective catalyst to promote borylation of arenes through C–H activation employing bis(pinacolato)diboron (1) as reagent leading to benzylic and aromatic borylation products. Interestingly, other related MOFs like MIL-101(Cr) and Al(OH)(BDC) (BDC: 1,4-benzenedicarboxylate) do not exhibit catalytic activity under identical conditions. Mechanistic studies using in-situ IR spectroscopy reveal that Cu ions play a crucial role in activating the arene and B–B bond in 1.
- Dhakshinamoorthy, Amarajothi,García, Cristina Vallés,Concepcion, Patricia,Garcia, Hermenegildo
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p. 212 - 217
(2020/07/06)
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- Preparation method of aryl borate catalyzed by cesium neovalerate
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The preparation method comprises the following steps: dissolving a compound of formula (I) and a diboron compound in an organic solvent, then adding an organic solvent dissolved with cesium neovalerate, palladium acetate and triphenylphosphine, and carrying out reaction to obtain aryl boronic acid ester. In the formula (I) R1. R2, R3, R4 and R5 are each independently selected from H, C. 1 - C10 Alkyl group, C2 - C10 Alkenyl, C2 - C10 Alkynyl group, C1 - C10 Alkoxy, hydroxy, hydroxy-substituted C1 - C10 Alkyl, phenyl, C1 - C10 Alkylamino. X Is selected from F, Cl, Br, i. The preparation method has the advantages of low production cost, high product yield, high purity, simple operation and suitability for industrial mass production.
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Paragraph 0034-0037; 0068-0069
(2021/09/22)
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- Catalytic Boration of Alkyl Halides with Borane without Hydrodehalogenation Enabled by Titanium Catalyst
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An unprecedented and general titanium-catalyzed boration of alkyl (pseudo)halides (alkyl-X, X=I, Br, Cl, OMs) with borane (HBpin, HBcat) is reported. The use of titanium catalyst can successfully suppress the undesired hydrodehalogenation products that prevail using other transition-metal catalysts. A series of synthetically useful alkyl boronate esters are readily obtained from various (primary, secondary, and tertiary) alkyl electrophiles, including unactivated alkyl chlorides, with tolerance of other reducing functional groups such as ester, alkene, and carbamate. Preliminary studies on the mechanism revealed a possible radical reaction pathway. Further extension of our strategy to aryl bromides is also demonstrated.
- Wang, Xianjin,Cui, Penglei,Xia, Chungu,Wu, Lipeng
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supporting information
p. 12298 - 12303
(2021/05/07)
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- Photo-induced thiolate catalytic activation of inert Caryl-hetero bonds for radical borylation
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Substantial effort is currently being devoted to obtaining photoredox catalysts with high redox power. Yet, it remains challenging to apply the currently established methods to the activation of bonds with high bond dissociation energy and to substrates with high reduction potentials. Herein, we introduce a novel photocatalytic strategy for the activation of inert substituted arenes for aryl borylation by using thiolate as a catalyst. This catalytic system exhibits strong reducing ability and engages non-activated Caryl–F, Caryl–X, Caryl–O, Caryl–N, and Caryl–S bonds in productive radical borylation reactions, thus expanding the available aryl radical precursor scope. Despite its high reducing power, the method has a broad substrate scope and good functional-group tolerance. Spectroscopic investigations and control experiments suggest the formation of a charge-transfer complex as the key step to activate the substrates.
- K?nig, Burkhard,Wang, Hua,Wang, Shun
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supporting information
p. 1653 - 1665
(2021/06/17)
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- Para-selective borylation of monosubstituted benzenes using a transient mediator
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Herein, we conceptualized a transient mediator approach that has the capability of para-selective C-H functionalization of monosubstituted aromatics. This approach is enabled by in situ generation of a versatile sulfonium salt via highly electrophilic phenoxathiine or thianthrene dication intermediate which can be readily generated from its sulfoxide with trifluoromethanesulfonic anhydride. Preliminary mechanistic study implied that the remarkable para selectivity might be related to the incredible electrophilicity of thianthrene dication intermediate. The versatility of this approach was demonstrated via para-borylation of various monosubstituted simple aromatics combining the sulfonium salt formation with further photocatalyzed transformation.
- Wu, Jie,Wang, Zengwei,Chen, Xiao-Yue,Wu, Yichen,Wang, Daoming,Peng, Qian,Wang, Peng
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p. 336 - 340
(2019/12/09)
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- Pd-Catalyzed Site-Selective Borylation of Simple Arenes via Thianthrenation?
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Site-selective borylation of simple arenes was realized in one pot via an electrophilic thianthrenation/Pd-catalyzed borylation sequence. The key to achieve this operatically simple process is the use of Pd catalysis, which could tolerate the solvent and acidic conditions used in the thianthrenation step. This protocol features mild conditions, broad functional group tolerance, and simple manipulations, and is suitable for late-stage functionalization of a wide range of pharmaceuticals and complex bioactive molecules.
- Chen, Xiao-Yue,Huang, Yu-Hao,Zhou, Jian,Wang, Peng
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supporting information
p. 1269 - 1272
(2020/08/13)
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- Nickel-Catalyzed C(sp2)-H Borylation of Arenes
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In this study, C(sp2)-H borylation of arenes was accomplished by a nickel catalyst, resulting in good yield. Alkyl and alkoxy arenes were successfully functionalized, affording C(sp2)-H borylated compounds. It was unraveled that the well-defined abnormal N-heterocyclic carbene based Ni(II) complex breaks into Ni nanoparticles (Ni-NPs), which act as catalytically active species. A series of controlled reactions under stoichiometric conditions along with spectroscopic studies and single-crystal X-ray crystallographic study helped us to understand the formation of Ni-NPs along with formation of a boron(III) compound during this reaction.
- Das, Arpan,Hota, Pradip Kumar,Mandal, Swadhin K.
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- Catalytic C?H Borylation Using Iron Complexes Bearing 4,5,6,7-Tetrahydroisoindol-2-ide-Based PNP-Type Pincer Ligand
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Catalytic C?H borylation has been reported using newly designed iron complexes bearing a 4,5,6,7-tetrahydroisoindol-2-ide-based PNP pincer ligand. The reaction tolerated various five-membered heteroarenes, such as pyrrole derivatives, as well as six-membered aromatic compounds, such as toluene. Successful examples of the iron-catalyzed sp3 C?H borylation of anisole derivatives were also presented.
- Kato, Takeru,Kuriyama, Shogo,Nakajima, Kazunari,Nishibayashi, Yoshiaki
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supporting information
p. 2097 - 2101
(2019/05/28)
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- Iron-catalyzed C-H borylation of arenes
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Well-defined iron bis(diphosphine) complexes are active catalysts for the dehydrogenative C-H borylation of aromatic and heteroaromatic derivatives with pinacolborane. The corresponding borylated compounds were isolated in moderate to good yields (25-73%) with a 5 mol% catalyst loading under UV irradiation (350 nm) at room temperature. Stoichiometric reactivity studies and isolation of an original trans-hydrido(boryl)iron complex, Fe(H)(Bpin)(dmpe)2, allowed us to propose a mechanism showing the role of some key catalytic species.
- Dombray, Thomas,Werncke, C. Gunnar,Jiang, Shi,Grellier, Mary,Vendier, Laure,Bontemps, Sébastien,Sortais, Jean-Baptiste,Sabo-Etienne, Sylviane,Darcel, Christophe
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supporting information
p. 4062 - 4065
(2015/04/14)
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- Para -C-H borylation of benzene derivatives by a bulky iridium catalyst
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A highly para-selective aromatic C-H borylation has been accomplished. By a new iridium catalyst bearing a bulky diphosphine ligand, Xyl-MeO-BIPHEP, the C-H borylation of monosubstituted benzenes can be affected with para-selectivity up to 91%. This catalytic system is quite different from the usual iridium catalysts that cannot distinguish meta- and para-C-H bonds of monosubstituted benzene derivatives, resulting in the preferred formation of meta-products. The para-selectivity increases with increasing bulkiness of the substituent on the arene, indicating that the regioselectivity of the present reaction is primarily controlled by steric repulsion between substrate and catalyst. Caramiphen, an anticholinergic drug used in the treatment of Parkinsons disease, was converted into five derivatives via our para-selective borylation. The present [Ir(cod)OH]2/Xyl-MeO-BIPHEP catalyst represents a unique, sterically controlled, para-selective, aromatic C-H borylation system that should find use in streamlined, predictable chemical synthesis and in the rapid discovery and optimization of pharmaceuticals and materials.
- Saito, Yutaro,Segawa, Yasutomo,Itami, Kenichiro
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supporting information
p. 5193 - 5198
(2015/05/05)
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- Nickel-catalyzed borylation of arenes and indoles via C-H bond cleavage
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The first nickel-catalyzed method for the borylation of carbon-hydrogen bonds in arenes and indoles is described. The use of an N-heterocyclic carbene ligand is essential for an efficient reaction, with an N-cyclohexyl-substituted derivative being optimal. This method is readily applied to the gram scale synthesis of 2-borylindole.
- Furukawa, Takayuki,Tobisu, Mamoru,Chatani, Naoto
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supporting information
p. 6508 - 6511
(2015/04/14)
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- PEPTIDASE INHIBITORS
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Novel compounds of the formula (I) wherein R1, R2, D, A, B and X have the meanings defined herein, pharmaceutical compositions comprising them as active ingredient, as well as their use in medicine, in particular as peptidase inhibitors, more specifically
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Page/Page column 164
(2012/10/18)
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- Hydride as a leaving group in the reaction of pinacolborane with halides under ambient Grignard and Barbier conditions. One-pot synthesis of alkyl, aryl, heteroaryl, vinyl, and allyl pinacolboronic esters
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Grignard reagents (aliphatic, aromatic, heteroaromatic, vinyl, or allylic) react with 1 equiv of 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (pinacolborane, PinBH) at ambient temperature in tetrahydrofuran (THF) to afford the corresponding pinacolboronates. The initially formed dialkoxy alkylborohydride intermediate quickly eliminates hydridomagnesium bromide (HMgBr) and affords the product boronic ester in very good yield. Hydridomagnesium bromide (HMgBr) in turn disproportionates to a 1:1 mixture of magnesium hydride (MgH2) and magnesium bromide (MgBr2) on addition of pentane to the reaction mixture. DFT calculations (Gaussian09) at the B3LYP/6-31G(d) level of theory show that disproportionation of HMgBr to MgH2 and MgBr2 is viable in the coordinating ethereal solvents. This reaction also can be carried out under Barbier conditions, where the neat PinBH is added to the flask prior to the in situ formation of Grignard reagent from the corresponding organic halide and magnesium metal. Pinacolboronic ester synthesis under Barbier conditions does not give Wurtz coupling side products from reactive halides, such as benzylic and allylic halides. The reaction between PinBH and various Grignard reagents is an efficient, mild, and general method for the synthesis of pinacolboronates.
- Clary, Jacob W.,Rettenmaier, Terry J.,Snelling, Rachel,Bryks, Whitney,Banwell, Jesse,Wipke, W. Todd,Singaram, Bakthan
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experimental part
p. 9602 - 9610
(2012/01/03)
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- PROCESS FOR PREPARING BORONIC ACIDS AND ESTERS IN THE PRESENCE OF MAGNESIUM METAL
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The present invention relates to the process for preparing a boronic acid or ester chemically, in which an aromatic compound is reacted with a boronating agent, in the presence of magnesium metal (Mg0). The invention also relates to the boronic acids or esters that can be obtained by means of this process and to the use thereof for example as a synthesis intermediate, in the Suzuki reaction, in the pharmaceutical or alternatively electronics field.
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Page/Page column 5-6
(2011/11/30)
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