- Enantioselective Copper-Catalyzed Synthesis of Trifluoromethyl-Cyclopropylboronates
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A copper-catalyzed enantioselective cyclopropanation involving trifluorodiazoethane in the presence of alkenyl boronates has been developed. This transformation enables the preparation of 2-substituted-3-(trifluoromethyl)cyclopropylboronates with high levels of stereocontrol. The products are valuable synthetic intermediates by transformation of the boronate group. This methodology can be applied to the synthesis of novel trifluoromethylated analogues of trans-2-arylcyclopropylamines, which are prevalent motifs in biologically active compounds.
- Altarejos, Julia,Carreras, Javier,Sucunza, David,Vaquero, Juan J.
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- Aqueous-Phase Synthesis of Size-Tunable Copper Nanocubes for Efficient Aryl Alkyne Hydroboration
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Copper nanocubes with average sizes of 82, 95, and 108 nm have been synthesized in an aqueous mixture of cetyltrimethylammonium chloride (CTAC) surfactant, copper acetate, and sodium ascorbate reductant heated at 100 °C for 40 min. Copper nanowires with a
- Thoka, Subashchandrabose,Madasu, Mahesh,Hsia, Chi-Fu,Liu, Shu-Ya,Huang, Michael H.
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- Iron-Catalyzed Dehydrogenative Borylation of Terminal Alkynes
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The catalytic system based on Fe(OTf)2 (2.5 mol%) and DABCO (1 mol%) selectively promotes the dehydrogenative borylation of both aromatic and aliphatic terminal alkynes to afford alkynylboronate derivatives in the presence of 1 equiv. of pinaco
- Wei, Duo,Carboni, Bertrand,Sortais, Jean-Baptiste,Darcel, Christophe
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- Hydroboration of Alkynes Catalyzed by Pyrrolide-Based PNP Pincer-Iron Complexes
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To utilize iron complexes as catalysts, the application of a well-designed ligand is critical to control the reactivity of the iron center. Recently, our group has succeeded in the synthesis of iron complexes bearing a pyrrolide-based PNP pincer ligand an
- Nakajima, Kazunari,Kato, Takeru,Nishibayashi, Yoshiaki
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- Aluminum-Catalyzed Selective Hydroboration of Nitriles and Alkynes: A Multifunctional Catalyst
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The reaction of LH [L = {(ArNH)(ArN)-C=N-C=(NAr)(NHAr)}; Ar =2,6-Et2-C6H3] with a commercially available alane amine adduct (H3Al·NMe2Et) in toluene resulted in the formation of a conjugated bis-guanidinate (CBG)-supported aluminum dihydride complex, i.e., LAlH2 (1), in good yield. The new complex has been thoroughly characterized by multinuclear magnetic resonance, IR, mass, and elemental analyses, including single-crystal structural studies. Further, we have demonstrated the aluminum-catalyzed hydroboration of a variety of nitriles and alkynes. Moreover, aluminum-catalyzed hydroboration is expanded to more challenging substrates such as alkene, pyridine, imine, carbodiimide, and isocyanides. More importantly, we have shown that the aluminum dihydride catalyzed both intra- A nd intermolecular chemoselective hydroboration of nitriles and alkynes over other reducible functionalities for the first time.
- Sarkar, Nabin,Bera, Subhadeep,Nembenna, Sharanappa
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- Aluminum-Hydride-Catalyzed Hydroboration of Carbon Dioxide
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This study describes the first use of a bis(phosphoranyl)methanido aluminum hydride, [ClC(PPh2NMes)2AlH2] (2, Mes = Me3C6H2), for the catalytic hydroboration of CO2. Complex 2 was synthesized by the reaction of a lithium carbenoid [Li(Cl)C(PPh2NMes)2] with 2 equiv of AlH3·NEtMe2 in toluene at -78 °C. 2 (10 mol %) was able to catalyze the reduction of CO2 with HBpin in C6D6 at 110 °C for 2 days to afford a mixture of methoxyborane [MeOBpin] (3a; yield: 78%, TOF: 0.16 h-1) and bis(boryl)oxide [pinBOBpin] (3b). When more potent [BH3·SMe2] was used instead of HBpin, the catalytic reaction was extremely pure, resulting in the formation of trimethyl borate [B(OMe)3] (3e) [catalytic loading: 1 mol % (10 mol %); reaction time: 60 min (5 min); yield: 97.6% (>99%); TOF: 292.8 h-1 (356.4 h-1)] and B2O3 (3f). Mechanistic studies show that the Al-H bond in complex 2 activated CO2 to form [ClC(PPh2NMes)2Al(H){OC(O)H}] (4), which was subsequently reacted with BH3·SMe2 to form 3e and 3f, along with the regeneration of complex 2. Complex 2 also shows good catalytic activity toward the hydroboration of carbonyl, nitrile, and alkyne derivatives.
- Chia, Cher-Chiek,Teo, Yeow-Chuan,Cham, Ning,Ho, Samuel Ying-Fu,Ng, Zhe-Hua,Toh, Hui-Min,Mézailles, Nicolas,So, Cheuk-Wai
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supporting information
p. 4569 - 4577
(2021/04/09)
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- Tropylium-Promoted Hydroboration Reactions: Mechanistic Insights Via Experimental and Computational Studies
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Hydroboration reaction of alkynes is one of the most synthetically powerful tools to access organoboron compounds, versatile precursors for cross-coupling chemistry. This type of reaction has traditionally been mediated by transition-metal or main group catalysts. Herein, we report a novel method using tropylium salts, typically known as organic oxidants and Lewis acids, to promote the hydroboration reaction of alkynes. A broad range of vinylboranes can be easily accessed via this metal-free protocol. Similar hydroboration reactions of alkenes and epoxides can also be efficiently catalyzed by the same tropylium catalysts. Experimental studies and DFT calculations suggested that the reaction follows an uncommon mechanistic pathway, which is triggered by the hydride abstraction of pinacolborane with tropylium ion. This is followed by a series ofin situcounterion-activated substituent exchanges to generate boron intermediates that promote the hydroboration reaction.
- Mai, Binh Khanh,Nguyen, Thanh Vinh,Ton, Nhan N. H.
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p. 9117 - 9133
(2021/07/19)
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- Copper-Photocatalyzed Hydroboration of Alkynes and Alkenes
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The photocatalytic hydroboration of alkenes and alkynes is reported. The use of newly-designed copper photocatalysts with B2Pin2 permits the formation a boryl radical, which is used for hydroboration of a large panel of alkenes and a
- Zhong, Mingbing,Gagné, Yohann,Hope, Taylor O.,Pannecoucke, Xavier,Frenette, Mathieu,Jubault, Philippe,Poisson, Thomas
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supporting information
p. 14498 - 14503
(2021/05/21)
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- Electrochemical Hydroboration of Alkynes
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Herein we reported the electrochemical hydroboration of alkynes by using B2Pin2 as the boron source. This unprecedented reaction manifold was applied to a broad range of alkynes, giving the hydroboration products in good to excellent yields without the need of a metal catalyst or a hydride source. This transformation relied on the possible electrochemical oxidation of an in situ formed borate. This anodic oxidation performed in an undivided cell allowed the formation of a putative boryl radical, which reacted on the alkyne.
- Aelterman, Maude,Jubault, Philippe,Poisson, Thomas,Sayes, Morgane
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supporting information
p. 8277 - 8282
(2021/05/27)
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- Cs4B4O3F10: First Fluorooxoborate with [BF4] Involving Heteroanionic Units and Extremely Low Melting Point
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Herein, a new congruently melting mixed-anion compound Cs4B4O3F10 has been characterized as the first fluorooxoborate with [BF4] involving heteroanionic units. Compound Cs4B4O3F10 possesses two highly fluorinated anionic clusters and therefore its formula can be expressed as Cs3(B3O3F6) ? Cs(BF4). The influence of [BF4] units on micro-symmetry and structural evolution was discussed based on the parent compound. More importantly, Cs4B4O3F10 shows the lowest melting point among all the available borates and thus sets a new record for such system. This work is of great significance to enrich and tailor the structure of borates using perfluorinated [BF4] units.
- Xia, Ming,Mutailipu, Miriding,Li, Fuming,Yang, Zhihua,Pan, Shilie
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supporting information
p. 9753 - 9757
(2021/05/27)
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- Z-Selective Alkyne Functionalization Catalyzed by a trans-Dihydride N-Heterocyclic Carbene (NHC) Iron Complex
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The Z-selective functionalization of terminal alkynes is a useful transformation in organic chemistry and mainly catalyzed by noble metals. Here, we present the Z-selective hydroboration of terminal alkynes catalyzed by a stable trans-dihydride iron compl
- De Ruiter, Graham,Fridman, Natalia,Garhwal, Subhash
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supporting information
p. 13817 - 13821
(2020/10/09)
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- Nickel(II)-Catalyzed Borylation of Alkenyl Methyl Ethers via C-O Bond Cleavage
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A new protocol has been developed for the borylation of conjugated alkenyl methyl ethers using B2Pin2 via C-O bond cleavage catalyzed by Ni(II). In this cross-coupling reaction, both E/Z isomers of alkenyl ethers are converted into (E)-alkenyl boronic esters with good reactivity. This transformation exhibits high chemoselectivity in the presence of competitive C-O bonds such as aryl ether, ester, amide, and thioether groups, thus providing a new method for the construction of various alkenyl boronates.
- Qiu, Xiaodong,Li, Yangyang,Zhou, Li,Chen, Peishan,Li, Fan,Zhang, Yanan,Ling, Yong
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supporting information
p. 6424 - 6428
(2020/08/24)
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- Practical Solvent-Free Microwave-Assisted Hydroboration of Alkynes
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A simple and rapid protocol for the anti-Markovnikov hydroboration of alkynes assisted by microwave irradiation has been developed. Pinacolborane smoothly reacts with terminal alkynes to obtain (E)-alkenyl boronates in good yields and short reactions times in the absence of solvent. Further transformations on the carbon-boron bond of the adducts can be sequentially achieved without the need of purifying the alkenyl boronates.
- Altarejos, Julia,Sucunza, David,Vaquero, Juan J.,Carreras, Javier
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p. 3024 - 3029
(2020/05/18)
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- Erratum: Markovnikov-selective hydroboration of olefins catalyzed by a copper N-heterocyclic carbene complex (Organometallics (2019) 38:17 (3322-3326) DOI: 10.1021/acs.organomet.9b00394)
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It has come to our attention that some of the products listed in Table 2 of the article and in eq 1 have the incorrect stereochemistry. The reactions of alkynes with HBpin give the linear E-olefin products, not the branched products as were shown. 1H NMR spectra clearly show two doublets with a large J (18 Hz) for the trans-hydrogens of the alkene product. A DEPT-135 spectrum also confirms that CH and not CH2 is present. Corrected eq 1, Table 2, TOC graphic are shown. Note that the alkene addition products are correctly assigned as branched, displaying a doublet and a quartet for the methyl and methane groups, respectively. NMR spectra for all products are included in the revised Supporting Information. We thank Prof. Jaesook Yun for pointing out this error, as her group has worked on related copper borylations for many years.
- DiBenedetto, Tarah A.,Parsons, Astrid M.,Jones, William D.
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supporting information
p. 3768 - 3769
(2020/11/17)
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- H2-Acceptorless Dehydrogenative Boration and Transfer Boration of Alkenes Enabled by Zirconium Catalyst
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The first example of an efficient and direct dehydrogenative boration of alkenes for vinyl boronate ester synthesis was achieved using a zirconium catalyst. Our methodology avoids using precious transition metals, additional hydrogen acceptors, high temperatures, and long reaction times, which were required to overcome the reducing ability of borane, to give alkyl boronate esters. Detailed mechanistic studies revealed a reversible reaction pathway and further suggested applying the zirconium complex as a “shuttle catalyst” for transfer boration, which thus sidesteps the use of relatively sensitive borane.
- Shi, Xiaonan,Li, Sida,Wu, Lipeng
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p. 16167 - 16171
(2019/11/03)
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- PEG-mediated recyclable borylative coupling of vinyl boronates with olefins
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This paper reports on the first green and sustainable repetitive batch borylative coupling of vinyl boronates with olefins by the effective immobilization of the [Ru(CO)Cl(H)(PCy3)2] catalyst in poly(ethylene glycols) with different molecular weights (Mw = 600–2000) and ending groups (OH, OMe, OSiMe3) or in biphasic poly(ethylene glycols)/supercritical CO2 (PEGs/scCO2) systems. Within this process, (E)-alkenyl boronates were obtained with high yields and excellent stereo-, regioselectivities. The best strategies permitted to carry out cross-coupling of vinyl boronates with styrene for up to 8–16 repetitive batches respectively, by applying 2 or 4 mol% of Ru-catalyst. The described methods enable the reuse of the TM-catalyst and solvents and the reduction or elimination of the use of volatile organic solvents and metal content in the final products, and obtain high cumulative TON values (up to 440). The biphasic systems also allowed the simplification of the separation procedure by effective product extraction in CO2 stream.
- Szyling,Walkowiak, J?drzej,Sokolnicki, Tomasz,Franczyk, Adrian,Stefanowska,Klarek, Mateusz
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p. 219 - 227
(2019/07/31)
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- Stereoselective Synthesis of Vinylboronates by Rh-Catalyzed Borylation of Stereoisomeric Mixtures
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The stereoselective preparation of vinylboronates via rhodium-catalyzed borylation of E/Z mixtures of vinyl actetates is described, and this method was also extended to synthesis of vinyldiboronates. These transformations feature high functional group compatibility and mild reaction conditions. Control experiments support a mechanism that involved a Rh-catalyzed borylation-isomerization sequence. The isomerization of (Z)-vinylboronates to (E)-isomers was also demonstrated.
- Li, Shenhuan,Li, Jie,Xia, Tianlai,Zhao, Wanxiang
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supporting information
p. 462 - 468
(2019/03/28)
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- NHC-copper-thiophene-2-carboxylate complex for the hydroboration of terminal alkynes
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An air-stable N-heterocyclic carbene-copper thiophene-2-carboxylate (CuTC) complex has been prepared for the stereoselective hydroboration of terminal alkynes using pinacolborane (HBpin) or 1,8-naphthalenediaminatoborane (HBdan). The newly synthesized complex can be directly activated by hydroboranes without a cocatalyst such as a base, and exhibits high reactivity for the hydroboration of alkynes under mild conditions. A gram-scale hydroboration of terminal phenylacetylene demonstrated the applicability of the copper complex for the preparation of alkenyl boronates.
- Jang, Won Jun,Kang, Byung-Nam,Lee, Ji Hun,Choi, Yoon Mi,Kim, Chong-Hyeak,Yun, Jaesook
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supporting information
p. 5249 - 5252
(2019/06/07)
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- Silver-Catalyzed anti-Markovnikov Hydroboration of C-C Multiple Bonds
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A simple silver salt (AgOAc)-catalyzed anti-Markovnikov-selective hydroboration of alkenes, 1,3-dienes, and alkynes with pinacolborane (HBpin) has been described. This strategy provides an efficient and practical method to access various alkyl-, allyl-, a
- Wang, Yan,Guan, Rui,Sivaguru, Paramasivam,Cong, Xuefeng,Bi, Xihe
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supporting information
p. 4035 - 4038
(2019/06/14)
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- Kinetics and Mechanism of the Arase-Hoshi R2BH-Catalyzed Alkyne Hydroboration: Alkenylboronate Generation via B-H/C-B Metathesis
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The mechanism of R2BH-catalyzed hydroboration of alkynes by 1,3,2-dioxaborolanes has been investigated by in situ 19F NMR spectroscopy, kinetic simulation, isotope entrainment, single-turnover labeling (10B/2H), and density functional theory (DFT) calculations. For the Cy2BH-catalyzed hydroboration 4-fluorophenylacetylene by pinacolborane, the resting state is the anti-Markovnikov addition product ArCH = CHBCy2. Irreversible and turnover-rate limiting reaction with pinacolborane (k ≈ 7 × 10-3 M-1 s-1) regenerates Cy2BH and releases E-Ar-CH═CHBpin. Two irreversible events proceed in concert with turnover. The first is a Markovnikov hydroboration leading to regioisomeric Ar-C(Bpin)═CH2. This is unreactive to pinacolborane at ambient temperature, resulting in catalyst inhibition every ~102 turnovers. The second is hydroboration of the alkenylboronate to give ArCH2CH(BCy2)Bpin, again leading to catalyst inhibition. 9-BBN behaves analogously to Cy2BH, but with higher anti-Markovnikov selectivity, a lower barrier to secondary hydroboration, and overall lower efficiency. The key process for turnover is B-H/C-B metathesis, proceeding by stereospecific transfer of the E-alkenyl group within a transient, μ-B-H-B bridged, 2-electron-3-center bonded B-C-B intermediate.
- Nieto-Sepulveda, Eduardo,Bage, Andrew D.,Evans, Louise A.,Hunt, Thomas A.,Leach, Andrew G.,Thomas, Stephen P.,Lloyd-Jones, Guy C.
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supporting information
p. 18600 - 18611
(2019/11/19)
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- AgSbF6-Catalyzed: Anti -Markovnikov hydroboration of terminal alkynes
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AgSbF6-Catalyzed anti-Markovnikov addition of pinacolborane (HBpin) to terminal alkynes to produce the E-vinylboronates is reported. This efficient methodology is scalable, compatible with sterically and electronically diverse alkynes, and works at room temperature under solvent-free condition. The utility of this method is demonstrated in the facile synthesis of the clinically important (E)-2,4,3′,5′-tetramethoxystilbene.
- Mamidala, Ramesh,Pandey, Vipin K.,Rit, Arnab
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supporting information
p. 989 - 992
(2019/01/23)
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- Transition-Metal-Free Deaminative Vinylation of Alkylamines
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The amino group is one of the most fundamental structural motifs in natural products and synthetic chemicals. However, amines potential as effective alkylating agents in organic synthesis is still problematic. A unified strategy has been established for deaminative vinylation of the alkylamines with vinyl boronic acids by C?N bond activation under catalyst-free conditions. The key to the high reactivity is the utilization of pyridinium salt-activated alkylamines, with a base as a promoter. The transformation exhibits good functional group compatibility, and includes inexpensive primary amine feedstocks and amino acids. The proposed method can serve as a powerful synthetic method for late-stage modification of complex compounds. Mechanistic experiments suggest that free radical processes are involved in this system. (Figure presented.).
- Hu, Jiefeng,Cheng, Bo,Yang, Xianyu,Loh, Teck-Peng
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supporting information
p. 4902 - 4908
(2019/09/13)
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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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- Selective and efficient synthesis of trans-arylvinylboronates and trans-hetarylvinylboronates using palladium catalyzed cross-coupling
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trans-Arylvinylboronate derivatives are important synthesis blocks in natural products, pharmaceuticals and organic materials. There are only a few reaction conditions that could selectively provide trans-arylvinylboronates by Heck coupling of pinacol vin
- Liu, Zhihao,Wei, Wei,Xiong, Lu,Feng, Qiang,Shi, Yaojie,Wang, Ningyu,Yu, Luoting
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supporting information
p. 3172 - 3176
(2017/04/14)
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- Isolation and characterization of hydrocarbon soluble NHC copper(I) phosphoranimide complex and catalytic application for alkyne hydroboration reaction
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Novel NHC copper(I) phosphoranimide complexes have been isolated and characterized by NMR and X-ray crystallography studies. The feature of this hydrocarbon soluble mononuclear copper complex as effective hydroboration catalyst could be attributed to the
- Bai, Tao,Yang, Yanhui,Han, Chao
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supporting information
p. 1523 - 1527
(2017/03/23)
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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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- Lewis acid catalysis: Catalytic hydroboration of alkynes initiated by Piers' borane
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Terminal and internal alkynes are efficiently hydroborated to (E)-alkenyl pinacol boronic esters with excellent yields and selectivities using a Lewis acid catalyst. In the case of Piers' borane (HB(C6F5)2) the borane acts as a pre-catalyst generating dissymmetrically gem-diborylated species of the form RCH2CR′(Bpin)(B(C6F5)2) which are the active catalysts.
- Fleige, Mirco,M?bus, Juri,Vom Stein, Thorsten,Glorius, Frank,Stephan, Douglas W.
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supporting information
p. 10830 - 10833
(2016/09/09)
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- Copper-catalyzed decarboxylative hydroboration: Synthesis of vinyl boronic esters
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Vinyl boronic esters were synthesized from aryl alkynyl carboxylic acids and bis(pinacolato)diboron using a copper-catalyzed decarboxylative reaction. The reaction was conducted with CuI (10 mol%), bis-[2-(diphenylphosphino)phenyl]ether(20 mol%), and LiOM
- Irudayanathan, Francis Mariaraj,Raja, Gabriel Charles Edwin,Kim, Han-Sung,Na, Kyungsu,Lee, Sunwoo
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p. 463 - 468
(2016/04/26)
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- Copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids under ligand-free or both ligand- and base-free conditions
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An efficient copper-catalyzed decarboxylative hydroboration of phenylpropiolic acids with bis(pinacolato)diboron was developed, affording β-vinylboronates as the only products in high yields. Extra hydrogen sources such as methanol are not needed in this
- Zhao, Ying-Wei,Feng, Qiang,Song, Qiu-Ling
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p. 571 - 574
(2016/04/26)
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- Ruthenium-catalyzed one-pot synthesis of (E)-(2-arylvinyl)boronates through an isomerization/cross-metathesis sequence from allyl-substituted aromatics
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We described the efficient preparation of (E)-(2-arylvinyl)boronates from allylbenzene derivatives on the basis of an isomerization/cross-metathesis sequence catalyzed by a modified Hoveyda-Grubbs catalyst. The implementation of the experimental procedure was simple and compatible with a large variety of substrates. This methodology provides a new chemical transformation not described to date. Allyl-substituted aromatics can thus be converted into diversely functionalized compounds, such as (E)-stilbene derivatives or (E)-vinyl azides, in only two steps. Copyright
- Hemelaere, Remy,Caijo, Frederic,Mauduit, Marc,Carreaux, Francois,Carboni, Bertrand
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supporting information
p. 3328 - 3333
(2014/06/09)
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- Formal anti-markovnikov hydroamination of terminal aryl alkynes with pinacolborane and hydroxylamines via Zr/Cu sequential catalysis
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We have explored a novel dry plasma process for the fabrication of electrodes on Nafion surfaces. Nanosized pillar structures were prepared through argon ion (Ar+) plasma treatment. The shear strengths of Au electrodes on plasma-treated Nafion surfaces were investigated. We found that the maximum shear strength (1.08 MPa) of Au-Nafion was observed under the optimal conditions (8 min, 100 W, 5 Pa, Ar+). Finally, we successfully prepared strongly bonded Au electrodes on Nafion through plasma surface treatment without using a wet plating process.
- Sakae, Ryosuke,Hirano, Koji,Satoh, Tetsuya,Miura, Masahiro
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p. 1128 - 1130
(2013/10/22)
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- Straightforward iron-catalyzed synthesis of vinylboronates by the hydroboration of alkynes
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An iron-catalyzed hydroboration of alkynes to produce vinylboronates has been examined. With a straightforward system composed of iron carbonyls and pinacolborane, good to excellent yields and chemoselectivities were achieved for a variety of alkynes. Cop
- Haberberger, Michael,Enthaler, Stephan
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supporting information
p. 50 - 54
(2013/02/23)
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- Catalytic non-conventional trans-hydroboration: A theoretical and experimental perspective
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We have studied the nonconventional trans-hydroboration reaction of alkynes both experimentally and theoretically. A catalytic system based on the in situ mixture of [{Rh- (cod)Cl}2]/PCy3 (cod=1,5-cyclooctadiene, Cy=cyclohexyl) has been able to activate pinacolborane and catecholborane and transfer boryl and hydride groups onto the same unhindered carbon atom of the terminal alkynes. The presence of a base (Et3N) favored the non-conventional trans-hydroboration over the traditional cis-hydroboration. Varying the substrate had a significant influence on the reaction, with up to 99% conversion and 94% regioselectivity observed for para-methyl- phenylacetylene. Both DFT and quantum mechanical/molecular mechanical ONIOM calculations were carried out on the [RhCl(PR3)2] system. To explain the selectivity towards the (Z)-alkenylboronate we explored several alternative mechanisms to the traditional cishydroboration, using propyne as a model alkyne. The proposed mechanism can be divided into four stages: 1) isomerization of the alkyne into the vinylidene, 2) oxidative addition of the borane reagent, 3) vinylidene insertion into the Rh-H bond, and finally 4) reductive elimination of the C-B bond to yield the 1-alkenylboronate. Calculations indicated that the vinylidene insertion is the selectivity- determining step. This result was consistent with the observed Z selectivity when the sterically demanding phosphine groups, such as PCy3 and PiPr3, were introduced. Finally, we theoretically analyzed the effect of the substrate on the selectivity; we identified several factors that contribute to the preference for aryl alkynes over aliphatic alkynes for the Z isomer. The intrinsic electronic properties of aryl substituents favored the Z-pathway over the E-pathway, and the aryl groups containing electron donating substituents favored the occurrence of the vinylidene reaction channel.
- Cid, Jessica,Carbo, Jorge J.,Fernandez, Elena
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supporting information; experimental part
p. 1512 - 1521
(2012/03/27)
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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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p. 7859 - 7871
(2011/06/27)
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- New anacardic acid-inspired benzamides: Histone lysine acetyltransferase activators
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A series of N-(4-cyano-3-trifluoromethyl-phenyl)-2-ethoxy-6-alkyl (and alkenyl) benzamides related to the anacardic acid derivative CTPB have been prepared from 2,6-dihydroxybenzoic acid with a Suzuki coupling and addition of the anion of 4-cyano-3-trifluoromethylphenylamine to a benzodioxinone as the key steps. In U937 cells, these analogues, in particular 7c, 7d, 7 f and 7j, induced cell-cycle arrest in the G1 phase, caused apoptosis in about 20% of the cells, and increased the acetylation levels of H3. These activities correlate with the enzymatic activation of histone lysine acetyltransferases (KATs): CBP and PCAF.
- Souto, Jose A.,Benedetti, Rosaria,Otto, Katharina,Miceli, Marco,Alvarez, Rosana,Altucci, Lucia,De Lera, Angel R.
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experimental part
p. 1530 - 1540
(2011/11/29)
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