- Advanced nanostructured catalysts for hydroboration
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Metal nanocrystals have been prepared in onium salts using supercritical carbon dioxide assisted synthesis. During the process, metal salts precursors are reduced by H2 in an organic solvent free media, the onium salts allowing both the stabili
- Liautard, Virginie,Pascu, Oana,Aymonier, Cyril,Pucheault, Mathieu
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Read Online
- A Chiral Naphthyridine Diimine Ligand Enables Nickel-Catalyzed Asymmetric Alkylidenecyclopropanations
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A novel class of chiral naphthyridine diimine ligands (NDI*) readily accessible from C2-symmetric 2,6-di-(1-arylethyl)anilines is described. The utility of these ligands, particularly one with fluorinated aryl side arms, is demonstrated by a reductive Ni-catalyzed enantioselective alkylidene transfer reaction from 1,1-dichloroalkenes to olefins. This transformation provides direct access to a broad range of synthetically valuable alkylidenecyclopropanes in high yields and enantioselectivities.
- Braconi, Elena,Cramer, Nicolai
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Read Online
- Synthesis method of 1-phenylvinyl borate
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The invention discloses a synthetic method of 1-phenylvinyl borate The preparation method comprises the following steps: by taking (1-bromovinyl)benzene 1 and diborate 2 as raw materials and sodium phenolate and potassium bromide as reaction reagents, heating the raw materials in methylbenzene to finish reaction, extracting, washing and concentrating the reaction solution to obtain a crude product, and performing pulping, low-temperature recrystallization and other operations which are easy for pilot scale-up to obtain the final product 1-phenylvinyl borate. The method replaces the raw material potassium phenate in the prior art, and the reagent cost is reduced. The invention solves the problems that in an existing route, raw materials are not easy to obtain, boric acid ester substituted products at different positions are easily generated, post-treatment needs column separation and the like and are not suitable for pilot scale-up. The invention provides a synthesis process which has the advantages of economical and easily available raw materials, good reaction selectivity and economical and easily operated post-treatment.
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Paragraph 0021-0030
(2021/03/31)
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- Hydroboration of Terminal Alkenes and trans-1,2-Diboration of Terminal Alkynes Catalyzed by a Manganese(I) Alkyl Complex
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A MnI-catalyzed hydroboration of terminal alkenes and a 1,2-diboration of terminal alkynes with pinacolborane (HBPin) is described. For alkenes, anti-Markovnikov hydroboration takes place; for alkynes the reaction proceeds with excellent trans-1,2-selectivity. The most active pre-catalyst is bench-stable alkyl bisphosphine MnI complex fac-[Mn(dippe)(CO)3(CH2CH2CH3)]. The catalytic process is initiated by migratory insertion of a CO ligand into the Mn–alkyl bond to yield an acyl intermediate, which undergoes B?H bond cleavage of HBPin (for alkenes) and rapid C?H bond cleavage (for alkynes), forming the active MnI boryl and acetylide catalysts [Mn(dippe)(CO)2(BPin)] and [Mn(dippe)(CO)2(C≡CR)], respectively. A broad variety of aromatic and aliphatic alkenes and alkynes was efficiently and selectively borylated. Mechanistic insights are provided based on experimental data and DFT calculations revealing that an acceptorless reaction is operating involving dihydrogen release.
- Kirchner, Karl,St?ger, Berthold,Veiros, Luis F.,Weber, Stefan,Zobernig, Daniel
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supporting information
p. 24488 - 24492
(2021/10/19)
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- Atroposelective Synthesis of Conjugated Diene-Based Axially Chiral Styrenes via Pd(II)-Catalyzed Thioether-Directed Alkenyl C-H Olefination
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The efficient stereoselective synthesis of conjugated dienes, especially those with axial chirality, remains a great challenge. Herein, we report the highly atroposelective synthesis of axially chiral styrenes with a conjugated 1,3-diene scaffold via a Pd(II)-catalyzed thioether-directed alkenyl C-H olefination strategy. This strategy features easy operation, mild reaction conditions, high functional group tolerance (69 examples), complete Z-selectivity, and excellent enantioselectivities (up to 99% ee). Notably, the highly enantioselective synthesis of atropisomers with two stereogenic axes were also achieved using this strategy (up to 99% ee and 97:3 dr). Moreover, the reaction could be scaled up, and the resulting axially chiral styrenes could be easily oxidized into chiral sulfoxide derivatives with high diastereoselectivities, which showed great promise as a new type of sulfur-olefin ligand.
- Jin, Liang,Zhang, Peng,Li, Ya,Yu, Xin,Shi, Bing-Feng
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p. 12335 - 12344
(2021/08/24)
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- Cyclic (Alkyl)(amino)carbene Ligands Enable Cu-Catalyzed Markovnikov Protoboration and Protosilylation of Terminal Alkynes: A Versatile Portal to Functionalized Alkenes**
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Regioselective hydrofunctionalization of alkynes represents a straightforward route to access alkenyl boronate and silane building blocks. In previously reported catalytic systems, high selectivity is achieved with a limited scope of substrates and/or rea
- Bertrand, Guy,Engle, Keary M.,Gao, Yang,Grotjahn, Douglas B.,Jazzar, Rodolphe,Junor, Glen P.,Kang, Taeho,Kendrick, Aaron,Yazdani, Sima
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supporting information
p. 19871 - 19878
(2021/08/13)
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- Synthesis of Alkenylboronates from N-Tosylhydrazones through Palladium-Catalyzed Carbene Migratory Insertion
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The palladium-catalyzed oxidative borylation reaction of N-tosylhydrazones has been developed. The reaction features mild conditions, broad substrate scope, and good functional group tolerance. It thus represents a highly efficient and practical method for the synthesis of di-, tri-, and tetrasubstituted alkenylboronates from readily available N-tosylhydrazones. One-pot Suzuki coupling and other transformations highlight the synthetic utility of the approach. DFT calculations have revealed that palladium-carbene formation and subsequent boryl migratory insertion are the key steps in the catalytic cycle. The high stereoselectivity observed in the formation of trisubstituted alkenylboronates has been explained by distortion-interaction analysis and NBO analysis.
- Chang, Taiwei,Huo, Jingfeng,Lei, Ming,Ping, Yifan,Wang, Jianbo,Wang, Qianyue,Wang, Rui
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supporting information
p. 9769 - 9780
(2021/07/19)
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- Enantioselective Allylation of Alkenyl Boronates Promotes a 1,2-Metalate Rearrangement with 1,3-Diastereocontrol
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Alkenyl boronates add to Ir(π-allyl) intermediates with high enantioselectivity. A 1,2-metalate shift forms a second C-C bond and sets a 1,3-stereochemical relationship. The three-component coupling provides tertiary boronic esters that can undergo multiple additional functionalizations. An extension to trisubstituted olefins sets three contiguous stereocenters.
- Davis, Colton R.,Luvaga, Irungu K.,Ready, Joseph M.
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supporting information
p. 4921 - 4927
(2021/05/04)
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- Cobalt-Catalyzed Markovnikov-Type Selective Hydroboration of Terminal Alkynes
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A cobalt-catalyzed Markovnikov-type hydroboration of terminal alkynes with HBpin to access α-alkenyl boronates with good regioselectivity and atom economy is reported. A new ligand has been developed for the cobalt hydride catalyst that has been used for a unique Markovnikov selective insertion of terminal alkynes into metal hydride bond. This operationally simple protocol exhibits excellent functional group tolerance to deliver valuable alkene derivatives.
- Chen, Jieping,Shen, Xuzhong,Lu, Zhan
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supporting information
p. 690 - 694
(2020/11/30)
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- Dehydrogenative Diboration of Alkynes Catalyzed by Ir/CO/tBuNC System
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Catalytic dehydrogenative diboration (DHDB) of alkyne with HBpin was achieved using [Ir(COD)Cl]2 and other related Ir precursors under CO atmosphere. The selectivity for DHDB over hydroboration was higher in less polar solvents and under higher
- Lai, Qingheng,Ozerov, Oleg V.
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- Reaction Pathways and Redox States in α-Selective Cobalt-Catalyzed Hydroborations of Alkynes
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Cobalt(II) alkyl complexes supported by a monoanionic NNN pincer ligand are pre-catalysts for the regioselective hydroboration of terminal alkynes, yielding the Markovnikov products with α:β-(E) ratios of up to 97:3. A cobalt(II) hydride and a cobalt(II) vinyl complex appear to determine the main reaction pathway. In a background reaction the highly reactive hydrido species specifically converts to a coordinatively unsaturated cobalt(I) complex which was found to re-enter the main catalytic cycle.
- Blasius, Clemens K.,Gade, Lutz H.,Matveeva, Regina,Vasilenko, Vladislav,Wadepohl, Hubert
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supporting information
p. 23010 - 23014
(2020/10/20)
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- Rhodium-catalysed diastereo- And enantioselective cyclopropanation of α-boryl styrenes
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A rhodium-catalyzed diastereo- and enantio-selective cyclopropanation of a-boryl styrenes with a-diazoarylacetates was established. Rh2(S-PTTL)4 (0.2 mol%) was found to be effective for the conversion, and 21 diastereopure cyclopropylboronates were prepared in high yields with excellent enantioselectivity (ee up to 99%).
- Sun, Xiao,Gu, Peiming,Qin, Jiao,Su, Yan
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supporting information
p. 12379 - 12382
(2020/10/30)
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- HETEROCYLCOALKENYL DERIVATIVES USEFUL AS AGONISTS OF THE GPR120 AND / OR GPR40
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The present invention is directed to heterocycloalkenyl derivatives, pharmaceutical compositions containing them and their use in the treatment of disorders and conditions modulated by the GPR120 and / or GPR40 receptors. 5 More particularly, the compound
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Page/Page column 109
(2019/10/01)
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- Markovnikov-Selective Hydroboration of Olefins Catalyzed by a Copper N-Heterocyclic Carbene Complex
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The efficient and atom-economical hydroboration of alkenes and alkynes using an N-heterocyclic carbene (NHC) copper hydroxide catalyst has been developed. An equimolar combination of substrate and HBpin allows for the selective Markovnikov hydroboration of alkenes and alkynes. A variety of functional groups were tolerated in good to excellent yield. This system features a facile reaction setup, atom economy, high selectivity, and an easily synthesized copper-NHC catalyst.
- Dibenedetto, Tarah A.,Parsons, Astrid M.,Jones, William D.
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supporting information
p. 3322 - 3326
(2019/09/30)
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- Vinylidenation of Organoboronic Esters Enabled by a Pd-Catalyzed Metallate Shift
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Organoboron “ate” complexes undergo a net vinyl insertion reaction to give 1,1-disubstituted alkenyl boronic esters when treated with stoichiometric allyl acetate and a palladium catalyst. Reactions that employ vinyllithium afforded good to excellent yields after one hour, while reactions that employ vinylmagnesium chloride furnished modest to good yields after 18 hours.
- Aparece, Mark D.,Gao, Chenpeng,Lovinger, Gabriel J.,Morken, James P.
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supporting information
p. 592 - 595
(2019/01/04)
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- Efficient Access to Chiral β-Borylated Carboxylic Esters via Rh-Catalyzed Hydrogenation
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Rh/bisphosphine?thiourea ligand (ZhaoPhos)-catalyzed asymmetric hydrogenation of (Z)-β-substituted-β-boryl-α,β-unsaturated esters was successfully developed, furnishing a variety of chiral β-borylated carboxylic esters with high yields and excellent enantioselectivities (up to 99% yield and >99% ee). The gram-scale asymmetric hydrogenation was performed efficiently in the presence of only 0.05 mol% (S/C=2 000) catalyst loading with full conversion, 99% yield and 99% ee. Moreover, the hydrogenation product was easily converted to other versatile synthetic intermediates, such as methyl (S)-3-hydroxy-3-phenylpropanoate and methyl (S)-3-(furan-2-yl)-3-phenylpropanoate. (Figure presented.).
- Liu, Gang,Li, Anqi,Qin, Xueyuan,Han, Zhengyu,Dong, Xiu-Qin,Zhang, Xumu
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supporting information
p. 2844 - 2848
(2019/04/26)
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- An Effective Catalytic Hydroboration of Alkynes in Supercritical CO2 under Repetitive Batch Mode
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A facile method for the synthesis of unsaturated organoboron compounds by hydroboration of terminal and internal alkynes in supercritical (sc) CO2 has been presented for the first time. The reactions performed in scCO2 in the presence of Ru catalysts (selectivity, productivity) are compared with those in a traditionally used solvent or without it. Moreover, the catalytic systems based on the application of scCO2 have been successfully tested for the processes under repetitive batch conditions. This strategy permitted us to obtain boryl-substituted olefins with high yields and selectivities up to the 16th catalytic cycle if using Ru(CO)Cl(H)(PPh3)3 as a catalyst. The process applied the self-dosing catalyst, which is gradually released to the reaction mixture under supercritical conditions in the individual batch. Such an approach has a positive impact on process sustainability and economy.
- Szyling, Jakub,Franczyk, Adrian,Stefanowska, Kinga,Klarek, Mateusz,Maciejewski, Hieronim,Walkowiak, J?drzej
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p. 531 - 539
(2018/02/14)
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- XBphos-Rh: A halogen-bond assembled supramolecular catalyst
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The use of halogen bonding as a tool to construct a catalyst backbone is reported. Specifically, pyridyl- and iodotetrafluoroaryl-substituted phosphines were assembled in the presence of a rhodium(i) precursor to form the corresponding halogen-bonded complex XBphos-Rh. The presence of fluorine substituents at the iodo-containing supramolecular motif was not necessary for halogen bonding to occur due to the template effect exerted by the rhodium center during formation of the halogen-bonded complex. The halogen-bonded supramolecular complexes were successfully tested in the catalytic hydroboration of terminal alkynes.
- Carreras, Lucas,Serrano-Torné, Marta,Van Leeuwen, Piet W. N. M.,Vidal-Ferran, Anton
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p. 3644 - 3648
(2018/04/26)
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- Soluble Platinum Nanoparticles Ligated by Long-Chain N-Heterocyclic Carbenes as Catalysts
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Soluble platinum nanoparticles (Pt NPs) ligated by two different long-chain N-heterocyclic carbenes (LC-IPr and LC-IMe) were synthesized and fully characterized by TEM, high-resolution TEM, wide-angle X-ray scattering (WAXS), X-ray photoelectron spectrosc
- Martínez-Prieto, Luis M.,Rakers, Lena,López-Vinasco, Angela M.,Cano, Israel,Coppel, Yannick,Philippot, Karine,Glorius, Frank,Chaudret, Bruno,van Leeuwen, Piet W. N. M.
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supporting information
p. 12779 - 12786
(2017/09/06)
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- Copper-catalyzed reductive borylations on water
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In this paper, we established copper catalyzed reductive borylation of terminal alkynes and diboron on water in the presence of amine. Moderate conditions enabled selective borylations of vinyl-substituted phenylacetylenes to undergo the borylation at a C–C triple bond. The Cu catalyst can be recycled for seven times.
- Tanaka, Chihiro,Nakamura, Kimiaki,Nishikata, Takashi
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p. 3999 - 4003
(2017/06/13)
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- Cyclodextrin Cavity-Induced Mechanistic Switch in Copper-Catalyzed Hydroboration
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N-heterocyclic carbene-capped cyclodextrin (ICyD) ligands, α-ICyD and β-ICyD derived from α- and β-cyclodextrin, respectively give opposite regioselectivities in a copper-catalyzed hydroboration. The site-selectivity results from two different mechanisms: the conventional parallel one and a new orthogonal mechanism. The shape of the cavity was shown not only to induce a regioselectivity switch but also a mechanistic switch. The scope of interest of the encapsulation of a reactive center is therefore broadened by this study.
- Zhang, Pinglu,Meijide Suárez, Jorge,Driant, Thomas,Derat, Etienne,Zhang, Yongmin,Ménand, Micka?l,Roland, Sylvain,Sollogoub, Matthieu
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supporting information
p. 10821 - 10825
(2017/08/30)
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- Copper-catalyzed regioselective hydroboration of terminal alkynes in aqueous medium
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A mild and environment-friendly copper-catalyzed hydroboration of terminal alkynes in aqueous medium was reported. Regioselectivity control was achieved in the presence of cyclodextrin-bispyridine ligand (CD-1). This protocol was successfully applied to inactivated terminal alkynes. Moreover, the ligand was recovered and reused without any loss of activity over five cycles.
- Yao, Zi-Jian,Hong, Shibin,Zhang, Wei,Liu, Mengyan,Deng, Wei
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supporting information
p. 910 - 913
(2016/02/05)
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- CuII-catalyzed regioselective borylation of alkynes and alkenes
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We developed a regioselective borylation of alkynes and alkenes protocol based on air-stable CuII/multi-dentate ligand system. Our catalytic system gives exclusive β-borylation products for most substrates in excellent chemical yields. We propo
- Liu, Shiwen,Zeng, Xiaojun,Xu, Bo
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supporting information
p. 3706 - 3710
(2016/07/26)
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- Synthesis of 1,3-Substituted Cyclobutanes by Allenoate-Alkene [2 + 2] Cycloaddition
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A method for the [2 + 2] cycloaddition of terminal alkenes with allenoates is presented. This process allows for the rapid synthesis of 1,3-substituted cyclobutanes in high yield under simple and robust reaction conditions.
- Conner, Michael L.,Brown, M. Kevin
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p. 8050 - 8060
(2016/09/09)
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- Speciation control during Suzuki-Miyaura cross-coupling of haloaryl and haloalkenyl MIDA boronic esters
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Boronic acid solution speciation can be controlled during the Suzuki-Miyaura cross-coupling of haloaryl N-methyliminodiacetic acid (MIDA) boronic esters to enable the formal homologation of boronic acid derivatives. The reaction is contingent upon control of the basic biphase and is thermodynamically driven: temperature control provides highly chemoselective access to either BMIDA adducts at room temperature or boronic acid pinacol ester (BPin) products at elevated temperature. Control experiments and solubility analyses have provided some insight into the mechanistic operation of the formal homologation process.
- Fyfe, James W. B.,Valverde, Elena,Seath, Ciaran P.,Kennedy, Alan R.,Redmond, Joanna M.,Anderson, Niall A.,Watson, Allan J. B.
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supporting information
p. 8951 - 8964
(2015/06/08)
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- Copper-catalyzed synthesis of 1,1-diborylalkanes through regioselective dihydroboration of terminal alkynes
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The copper-catalyzed sequential hydroboration of terminal alkynes with pinacolborane to prepare 1,1-diborylalkanes directly from alkynes was studied. Protected propargyl amines, propargyl alcohol derivatives, and simple alkynes regioselectively produced t
- Lee, Sumin,Li, Dingxi,Yun, Jaesook
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supporting information
p. 2440 - 2443
(2014/11/08)
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- Stereoselective formation of trisubstituted vinyl boronate esters by the acid-mediated elimination of α-hydroxyboronate esters
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The copper-catalyzed diboration of ketones followed by an acid-catalyzed elimination leads to the formation of 1,1-disubstituted and trisubstituted vinyl boronate esters with moderate to good yields and selectivity. Addition of tosic acid to the crude diboration products provides the corresponding vinyl boronate esters upon elimination. The trisubstituted vinyl boronate esters are formed as the (Z)-olefin isomer, which was established by subjecting the products to a Suzuki-Miyaura coupling reaction to obtain alkenes of known geometry.
- Guan, Weiye,Michael, Alicia K.,McIntosh, Melissa L.,Koren-Selfridge, Liza,Scott, John P.,Clark, Timothy B.
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p. 7199 - 7204
(2014/08/18)
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- SYNTHESIS OF BORONIC ESTERS AND BORONIC ACIDS USING GRIGNARD REAGENTS
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Boronic esters and boronic acids are synthesized at ambient temperature in an ethereal solvent by the reaction of Grignard reagents with a boron-containing substrate. The boron-containing substrate may be a boronic ester such as pinacolborane, neopentylglycolborane, or a dialkylaminoborane compound such as diisopropylaminoborane. The Grignard reagents may be preformed or generated from an alkyl, alkenyl, aryl, arylalkyl, heteroaryl, vinyl, or allyl halide compound and Mg°. When the boron-containing substrate is a boronic ester, the reactions generally proceed at room temperature without added base in about 1 to 3 hours to form a boronic ester compound. When the boron-containing substrate is a dialkylaminoborane compound, the reactions generally proceed to completion at 0°C in about 1 hour to form a boronic acid compound.
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Paragraph 0075; 0087
(2013/03/26)
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- Evaluation of endo- and exo-aryl-substitutions and central scaffold modifications on diphenyl substituted alkanes as 5-lipoxygenase activating protein inhibitors
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A search for a suitable replacement for the central norbornyl scaffold presented in the recently disclosed novel FLAP inhibitors is herein described, as well as the SAR study performed on the endo and exo-aryl groups.
- Chu, Lin,Armstrong, Helen M.,Chang, Linda L.,Cheng, Amy F.,Colwell, Lawrence,Cui, Jisong,Evans, Jilly,Galka, Amy,Goulet, Mark T.,Hayes, Nancy,Lo, Jane,Menke, John,Ok, Hyun O.,Ondeyka, Debra L.,Patel, Minal,Quaker, Grace M.,Sings, Heather,Witkin, Stephanie L.,Zhao, Annie,Ujjainwalla, Feroze
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scheme or table
p. 4133 - 4138
(2012/07/03)
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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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- Highly selective methods for synthesis of internal (α-) vinylboronates through efficient NHC-Cu-catalyzed hydroboration of terminal alkynes. Utility in chemical synthesis and mechanistic basis for selectivity
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Cu-catalyzed methods for site-selective hydroboration of terminal alkynes, where the internal or α-vinylboronate is generated predominantly (up to >98%) are presented. Reactions are catalyzed by 1-5 mol % of N-heterocyclic carbene (NHC) complexes of copper, easily prepared from N-aryl-substituted commercially available imidazolinium salts, and proceed in the presence of commercially available bis(pinacolato)diboron [B2(pin)2] and 1.1 equiv of MeOH at -50 to -15 °C in 3-24 h. Propargyl alcohol and amine and the derived benzyl, tert-butyl, or silyl ethers as well as various amides are particularly effective substrates; also suitable are a wide range of aryl-substituted terminal alkynes, where higher α-selectivity is achieved with substrates that bear an electron-withdrawing substituent. α-Selective Cu-catalyzed hydroborations are amenable to gram-scale procedures (1 mol % catalyst loading). Mechanistic studies are presented, indicating that α selectivity arises from the structural and electronic attributes of the NHC ligands and the alkyne substrates. Consistent with suggested hypotheses, catalytic reactions with a Cu complex, derived from an N-adamantyl-substituted imidazolinium salt, afford high β selectivity with the same class of substrates and under similar conditions.
- Jang, Hwanjong,Zhugralin, Adil R.,Lee, Yunmi,Hoveyda, Amir H.
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scheme or table
p. 7859 - 7871
(2011/06/27)
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- α-Selective Ni-catalyzed hydroalumination of aryl- and alkyl-substituted terminal alkynes: Practical syntheses of internal vinyl aluminums, halides, or boronates
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A method for Ni-catalyzed hydroalumination of terminal alkynes, leading to the formation of α-vinylaluminum isomers efficiently (>98% conv in 2-12 h) and with high selectivity (95% to >98% α), is described. Catalytic α-selective hydroalumination reactions proceed in the presence of a reagent (diisobutylaluminum hydride; dibal-H) and 3.0 mol % metal complex (Ni(dppp)Cl2) that are commercially available and inexpensive. Under the same conditions, but with Ni(PPh3)2Cl2, hydroalumination becomes highly β-selective, and, unlike uncatalyzed transformations with dibal-H, generates little or no alkynylaluminum byproducts. All hydrometalation reactions are reliable, operationally simple, and practical and afford an assortment of vinylaluminums that are otherwise not easily accessible. The derived α-vinyl halides and boronates can be synthesized through direct treatment with the appropriate electrophiles [e.g., Br 2 and methoxy(pinacolato)boron, respectively]. Ni-catalyzed hydroaluminations can be performed with as little as 0.1 mol % catalyst and on gram scale with equally high efficiency and selectivity.
- Gao, Fang,Hoveyda, Amir H.
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supporting information; scheme or table
p. 10961 - 10963
(2010/09/17)
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- N-Heterocyclic carbenes: deducing σ- and π-contributions in Rh-catalyzed hydroboration and Pd-catalyzed coupling reactions
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The effect of tuning the electronic properties of N-heterocyclic carbene (NHC) ligands was evaluated in multiple, mechanistically distinct, metal-mediated reactions. Hydroboration and Heck reactions, catalyzed by Rh-NHC and Pd-NHC complexes, respectively,
- Khramov, Dimitri M.,Rosen, Evelyn L.,Er, Joyce A.V.,Vu, Peter D.,Lynch, Vincent M.,Bielawski, Christopher W.
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p. 6853 - 6862
(2008/12/20)
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- Palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with 1-alkenyl halides or triflates: Convenient synthesis of unsymmetrical 1,3-dienes via the borylation-coupling sequence
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The synthesis of 1-alkenylboronic acid pinacol esters via a palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron (pin2B2, pin = Me4C2O2) with 1-alkenyl halides or triflates was carrie
- Takagi, Jun,Takahashi, Kou,Ishiyama, Tatsuo,Miyaura, Norio
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p. 8001 - 8006
(2007/10/03)
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- Asymmetric hydrogenation of 1-phenylethenylboronic acid and esters for the synthesis of chiral organoboron compounds
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The hydrogenation of ethanediol 1-phenylethenylboronic ester was carried out at -20 °C under a hydrogen atmosphere (9 atm) in the presence of [Rh(cod)2]BF4-(R)-BINAP (3 mol%). After alkaline hydrogen peroxide oxidation, the reaction gave 1-phenylethanol with 80% e.e.
- Ueda, Masato,Saitoh, Atsushi,Miyaura, Norio
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p. 145 - 147
(2007/10/03)
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- Highly efficient monophosphine platinum catalysts for alkyne diboration
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Automated parallel screening using a series of in situ generated platinum(0) phosphine complexes has allowed the identification of improved catalysts for the diboration of alkynes using bis(pinacolato)diboron (B2(pin)2, pin = OCMe2CMe2O). A selection of phosphines were added to [Pt(NBE)3] (NBE = norbornene), which contains only labile mono-olefin ligands, and the activity of the resulting solutions as catalysts for the diboration of 4-CF3C6H4C≡CC6H 4CF3-4′ 1 by B2(pin)2 was investigated by in situ GC-MS and/or NMR spectroscopy. This allowed the optimum phosphine : platinum stoichiometry to be identified as 1 : 1, and the large differences in catalyst activity depending on the nature of the phosphine to be quantified. The best phosphines employed in the study, PCy3 and PPh2(o-Tol) (o-Tol = C6H4Me-o), give activities orders of magnitude greater than the worst, such as P(C6F5)3 and PBut3. The monophosphine catalysts function much more efficiently than previous catalysts for a range of alkynes allowing diborations to be performed at ambient temperatures. The diboration of strained cyclic alkenes and some vinyl- and allyl-arenes proceeded well, although the catalysts were inactive for other olefinic systems examined. As a result of these studies, the isolable and stable compound [Pt(PCy3)(η2-C2H4) 2] was identified as an excellent catalyst for alkyne diboration even at room temperature.
- Thomas,Souza,Marder
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p. 1650 - 1656
(2007/10/03)
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- A borylcopper species generated from bis(pinacolato)diboron and its additions to α,β-unsaturated carbonyl compounds and terminal alkynes
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The addition of bis(pinacolato)diboron [(Me4C2O2)B-B(O2C2Me 4)] to α,β-unsaturated carbonyl compounds giving β-boryl carbonyl compounds and the addition to terminal alkynes yielding either 2-boryl-1-alkenes or 1-boryl-1-alkenes were carried out in DMF at room temperature in the presence of CuCl and AcOK. The transmetalation between diboron and [Cu(Cl)OAc]K generating a borylcopper species was proposed as the key step in the reactions because CuOAc similarly mediated both addition reactions to enones and alkynes in the presence of LiCl.
- Takahashi, Kou,Ishiyama, Tatsuo,Miyaura, Norio
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- Synthesis of 1-alkenylboronic esters via palladium-catalyzed cross-coupling reaction of bis(pinacolato)diboron with 1-alkenyl halides and triflates
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The synthesis of 1-alkenylboronic acid pinacol esters via the palladium-catalyzed cross-coupling reaction of 1-alkenyl halides or triflates with bis(pinacolato)diboron [(Me4C2O2)B-B(O2C2Me 4/sub
- Takahashi, Kou,Takagi, Jun,Ishiyama, Tatsuo,Miyaura, Norio
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p. 126 - 127
(2007/10/03)
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