- Infrared spectra of B(OMe)3, ClB(OMe)2 and Cl2BOMe species, isolated CH streching frequencies and bond strengths
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Infrared spectra in the gas phase are reported over the range 3100-500 cm-1 for species of B(OMe)3, ClB(OMe)2 and Cl2BOMe, with CH3, CD3 and CHD2 substitution.A detailed analysis of νCH and νCD data in all three species of Cl2BOMe yields strong evidence for the presence of three kinds of CH bond, two of them weak and one of them strong.The methyl group is then twisted, probably through 10-20 deg, out of the eclipsed or staggered conformation.The CHD2 spectra of the di and trimethoxy compounds are less susceptible to analysis, but suggest also the presence of two weak and strong bonds, the former increasing in weakness as the number of methoxy groups increases.This is as expected from the increased competition likely between the lone pair electrons for the empty boron orbital.The spectra of the CD3 species permit a clear assignment of νBO, δsCH3, δsCD3 and δasCD3 modes.In Cl(COCH3)2, νsBO lies at 1278 cm-1.
- McKean, D. C.,Coats, A. M.
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- Rehydrogenation of aminoboranes to amine-boranes using H2O: Reaction scope and mechanism
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Water has been successfully employed as a reagent with which to rehydrogenate aminoboranes (e.g., iPr2N=BH2, 2,2,6,6-Me4C5H6N=BH2, and also transient Me2N=BH2 derived from 1/2[Me2N-BH2]2) to amine-boranes (e.g., iPr2NH·BH3, 2,2,6,6-Me4C5H6NH·BH3, Me2NH·BH3) in approximately 30 yield. The conversion to amine-boranes from the corresponding aminoboranes using this method represents an example of a metal-free, single-step route for the hydrogenation of the B=N bond. Deuterium labeling studies indicated that the protic hydrogen (N-H) on the rehydrogenated amine-borane was derived from H2O, whereas the third hydridic hydrogen (B-H) on the amine-borane was generated from the formation of a postulated hydride-bridged intermediate H2B(μ-H)(μ-NR2)B(OH)H (R2 = Me2, iPr2, 2,2,6,6-Me4C5H6), which requires a second equivalent of the starting aminoborane, thus explaining the low yield. Formation of insoluble borates (BxOyHz) provides a driving force for the reaction. Significantly, the yield can be increased by adding a sacrificial source of BH3 (e.g., to ca. 53% for BH3·THF) or by adding a separate source of H- (e.g., to ca. 95% for LiBH4) to complement the H+ (from H2O) in a more atom-efficient reaction.
- Leitao, Erin M.,Manners, Ian
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- Study of the reaction between boron trifluoride methanol complex and sodium methoxide
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The reaction between boron trifluoride methanol complex and sodium methoxide in methanol solution was investigated using conductivity as the reaction indicator. The reaction conditions were examined and a mechanism of this reaction was proposed. Moreover, proper reaction conditions were proposed for boric acid preparation using this reaction. 2014
- Wuke, Lang,Weijiang, Zhang,Jiao, Xu,Lei, Zhang
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- Preparation of energetic poly(azolyl)borates as new environmentally benign green-light-emitting species for pyrotechnics
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Three different energetic poly(azolyl)borates, potassium dihydridobis(4-nitroimidazolyl)borate, sodium dihydridobis(4, 5-dinitroimidazolyl)borate, and sodium dihydridobis(3, 4,5-trinitropyrazolyl) borate, were synthesized as starting materials for metal-f
- Klapoetke, Thomas M.,Rusan, Magdalena,Sproll, Veronique
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- Pseudo Halide Chemistry in Ionic Liquids with Decomposable Anions
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Several pseudohalide containing ionic liquids with quarternary ammonium counter cations of the general formula [R3MeN]X [R = ethyl (1X), n-butyl (2X) with X– = CN–, N3 –, OCN–, and SCN–] were synthesized by decomposition of the corresponding trialkylammonium methylcarbonate in the reaction with Me3Si–X. We also treated 2CN with OP(OMe)3, yielding [nBu3MeN][O2P(OMe)2] and acetonitrile (Me-CN). The double salt [nBu3MeN]2{[B(OMe)3(CN)](CN)} was obtained from the reaction of 2CN with B(OMe)3, featuring the formation of the monocyanotrimethoxyborate anion, [B(OMe)3(CN)]–, co-crystallized with [nBu3MeN]CN. [nBu3MeN]2{[B(OMe)3(CN)](CN)} was fully characterized including structure elucidation.
- Harloff, J?rg,Schulz, Axel,Stoer, Philip,Villinger, Alexander
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- Reaction of a 14-vertex carborane with nucleophiles: Formation of nido-C2B12, nido-C2B11, and closo-CB11 carborane anions
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Nucleophilic reactions of a 14-vertex closo-carborane are reported. 2, 3-(CH2)3-2,3-C2B12H12 (1) reacts with MeOH at 70 °C to give closo-CB11 anions [1,2-(CH2)3CH(OMe)-1-CB11, H10] - ([2a]-), [1,2-(CH2)3CH(OMe)-1- CB11, H10]- ([2b]- ), and [1,2-(CH2)2CH=CH-1-CB11H10] - ([2c]- ). It is suggested that [2c]- is an intermediate for the isomerizatlon from [2a]- to [2b]- . Treatment of 1 with MeOH/Me3N, 'BuOK or LINMe2 affords nido-C2B12 species [8,9-(CH2) 3-μ-11, 12-(Nu)BH-8,9-C2B11H 11]-(Nu = MeO ([3a]-), BuO ([3b]-), and Me2N ([3c]-)). In the presence of acid such as HCl, anions [3]- are converted to 1. However, [3] undergo deboration reaction, in the presence of bases, to generate a nidO-C2B 11 anion [8, 9-(CH2)38,9-C2B 11H12]- ([4]-) that can also be formed directly from the reaction of 1 with excess CsF or piperidine. Mechanistic studies show that [3a]- is the first intermediate in the reaction of 1 with MeOH and [4]- Is unlikely an intermediate.
- Zhang, Jian,Zheng, Fangrui,Chan, Hoi-Shan,Xie, Zuowei
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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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- Acetate-catalyzed hydroboration of CO2 for the selective formation of methanol-equivalent products
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The present study details the use of the acetate anion, an inexpensive and robust anion, as a CO2 hydroboration catalyst for the selective formation, in most cases, of methanol-equivalent borane products. Thus, upon heating (90 °C, PhBr), tetrabutylammonium, sodium and potassium acetate (1, 2 and 3, respectively) effectively catalyze CO2 hydroboration by pinacolborane (pinB-H) to afford CO2 reduction products HOCOBpin (A), pinBOCH2OBpin (B) and methoxyborane (C). In most cases, high selectivity for product C with higher borane loading and longer reaction time with a TON of up to 970 was observed. The reduction catalysis remains efficient at low catalyst loading (down to 0.1 mol%) and may also be performed under solvent-free conditions using salt 1 as a catalyst, reflecting the excellent robustness and stability of the acetate anion. In control experiments, a 1/1 1/pinB-H mixture was found to react fast with CO2 at room temperature to produce formate species [pinB(O2CH)(OAc)][N(nBu)4] (5) through CO2 insertion into the B-H bond. DFT calculations were also performed to gain insight into the acetate-mediated CO2 hydroboration catalysis, which further supported the crucial role of acetate as a Lewis base in CO2 functionalization catalysis by pinB-H. The DFT-estimated mechanism is in line with experimental data and rationalizes the formation of the most thermodynamically stable reduction product C through acetate catalysis.
- Dagorne, Samuel,Dos Santos, Jo?o H. Z.,Jacques, Béatrice,López, Carlos Silva,Nieto Faza, Olalla,Schrekker, Henri S.,Sokolovicz, Yuri C. A.,Specklin, David
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p. 2407 - 2414
(2020/05/13)
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- Ph2PCH2CH2B(C8H14) and Its Formaldehyde Adduct as Catalysts for the Reduction of CO2with Hydroboranes
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We study two metal-free catalysts for the reduction of CO2 with four different hydroboranes and try to identify mechanistically relevant intermediate species. The catalysts are the phosphinoborane Ph2P(CH2)2BBN (1), easily accessible in a one-step synthesis from diphenyl(vinyl)phosphine and 9-borabicyclo[3.3.1]nonane (H-BBN), and its formaldehyde adduct Ph2P(CH2)2BBN(CH2O) (2), detected in the catalytic reduction of CO2 with 1 as the catalyst but properly prepared from compound 1 and p-formaldehyde. Reduction of CO2 with H-BBN gave mixtures of CH2(OBBN)2 (A) and CH3OBBN (B) using both catalysts. Stoichiometric and kinetic studies allowed us to unveil the key role played in this reaction by the formaldehyde adduct 2 and other formaldehyde-formate species, such as the polymeric BBN(CH2)2(Ph2P)(CH2O)BBN(HCO2) (3) and the bisformate macrocycle BBN(CH2)2(Ph2P)(CH2O)BBN(HCO2)BBN(HCO2) (4), whose structures were confirmed by diffractometric analysis. Reduction of CO2 with catecholborane (HBcat) led to MeOBcat (C) exclusively. Another key intermediate was identified in the reaction of 2 with the borane and CO2, this being the bisformaldehyde-formate macrocycle (HCO2){BBN(CH2)2(Ph2P)(CH2O)}2Bcat (5), which was also structurally characterized by X-ray analysis. In contrast, using pinacolborane (HBpin) as the reductant with catalysts 1 and 2 usually led to mixtures of mono-, di-, and trihydroboration products HCO2Bpin (D), CH2(OBpin)2 (E), and CH3OBpin (F). Stoichiometric studies allowed us to detect another formaldehyde-formate species, (HCO2)BBN(CH2)2(Ph2P)(CH2O)Bpin (6), which may play an important role in the catalytic reaction. Finally, only the formaldehyde adduct 2 turned out to be active in the catalytic hydroboration of CO2 using BH3·SMe2 as the reductant, yielding a mixture of two methanol-level products, [(OMe)BO]3 (G, major product) and B(OMe)3 (H, minor product). In this transformation, the Lewis adduct (BH3)Ph2P(CH2)2BBN was identified as the resting state of the catalyst, whereas an intermediate tentatively formulated as the Lewis adduct of compound 2 and BH3 was detected in solution in a stoichiometric experiment and is likely to be mechanistically relevant for the catalytic reaction.
- Ramos, Alberto,Anti?olo, Antonio,Carrillo-Hermosilla, Fernando,Fernández-Galán, Rafael
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supporting information
p. 9998 - 10012
(2020/07/24)
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- A Versatile NHC-Parent Silyliumylidene Cation for Catalytic Chemo- And Regioselective Hydroboration
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This study describes the first use of a silicon(II) complex, NHC-parent silyliumylidene cation complex [(IMe)2SiH]I (1, IMe =:C{N(Me)C(Me)}2) as a versatile catalyst in organic synthesis. Complex 1 (loading: 10 mol %) was shown to act as an efficient catalyst (reaction time: 0.08 h, yield: 94%, TOF = 113.2 h-1 reaction time: 0.17 h, yield: 98%, TOF = 58.7 h-1) for the selective reduction of CO2 with pinacolborane (HBpin) to form the primarily reduced formoxyborane [pinBOC(-O)H]. The activity is better than the currently available base-metal catalysts used for this reaction. It also catalyzed the chemo- and regioselective hydroboration of carbonyl compounds and pyridine derivatives to form borate esters and N-boryl-1,4-dihydropyridine derivatives with quantitative conversions, respectively. Mechanistic studies show that the silicon(II) center in complex 1 activated the substrates and then mediated the catalytic hydroboration. In addition, complex 1 was slightly converted into the NHC-borylsilyliumylidene complex [(IMe)2SiBpin]I (3) in the catalysis, which was also able to mediate the catalytic hydroboration.
- Leong, Bi-Xiang,Lee, Jiawen,Li, Yan,Yang, Ming-Chung,Siu, Chi-Kit,Su, Ming-Der,So, Cheuk-Wai
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supporting information
p. 17629 - 17636
(2019/11/11)
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- Carbodiimides as catalysts for the reduction of CO2 with boranes
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Carbodiimides catalyse the reduction of CO2 with H-BBN or BH3·SMe2 to give either mixtures of CH2(OBBN)2 and CH3OBBN or (MeOBO)3 and B(OMe)3 under mild conditions (25-60 °C, 1 atm CO2). Stoichiometric reactions and theoretical calculations were performed to unveil the mechanism of these catalytic processes.
- Ramos, Alberto,Anti?olo, Antonio,Carrillo-Hermosilla, Fernando,Fernández-Galán, Rafael,Rodríguez-Diéguez, Antonio,García-Vivó, Daniel
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supporting information
p. 4700 - 4703
(2018/05/22)
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- A continuous reaction distillation process for preparing methyl borate method
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The invention provides a novel process method for preparing trimethyl borate through continuous reactive distillation. The process method comprises the following steps of: (1) continuously feeding methyl alcohol and boric acid into a reaction kettle based on ratio to realize initial reaction; (2) continuously feeding reaction liquid into a rough evaporating kettle to evaporate; transferring methyl alcohol, trimethyl borate and water into a reactive distillation tower in form of mixed gas by a evaporating manner; continuously draining water produced in the reaction of methyl alcohol and trimethyl borate from the bottom of the tower; carrying out reaction for producing trimethyl borate after the water is drained until boric acid is completely reacted, so as to improve the one-time conversion rate of boric acid to be more than 99.5% as well as reduce the mixing ratio of methyl alcohol, wherein the energy consumption in preparation of trimethyl borate is greatly lowered down, all discharges from the bottom of the tower are the water produced in the reaction, and little boric acid and methyl alcohol are left; and (3) transferring trimethyl borate output from the reactive distillation tower by an evaporating manner into an azeotropic distillation tower together with methyl alcohol, lowering down the temperature of absolute methanol at the bottom part of the zeotropic distillation tower and recovering the absolute methanol, recovering azeotrope of trimethyl borate and methyl alcohol from the top of the tower, and then separating the azeotrope to obtain trimethyl borate.
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Paragraph 0028-0034
(2017/03/17)
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- Ligand-Controlled Cobalt-Catalyzed Transfer Hydrogenation of Alkynes: Stereodivergent Synthesis of Z- and E-Alkenes
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Herein, we report a novel cobalt-catalyzed stereodivergent transfer hydrogenation of alkynes to Z- and E-alkenes. Effective selectivity control is achieved based on a rational catalyst design. Moreover, this mild system allows for the transfer hydrogenation of alkynes bearing a wide range of functional groups in good yields using catalyst loadings as low as 0.2 mol %. The general applicability of this procedure is highlighted by the synthesis of more than 50 alkenes with good chemo- and stereoselectivity. A preliminary mechanistic study revealed that E-alkene product was generated via sequential alkyne hydrogenation to give Z-alkene intermediate, followed by a Z to E alkene isomerization process.
- Fu, Shaomin,Chen, Nan-Yu,Liu, Xufang,Shao, Zhihui,Luo, Shu-Ping,Liu, Qiang
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supporting information
p. 8588 - 8594
(2016/07/27)
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- BH3 Activation by Phosphorus-Stabilized Geminal Dianions: Synthesis of Ambiphilic Organoborane, DFT Studies, and Catalytic CO2 Reduction into Methanol Derivatives
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The reaction of the geminal dianion (SCS)2- 1 with 2 equiv of BH3·SMe2 leads to the isolation and full characterization of the new organoborane [(SCS)BH2][Li(THF)2] 2, in which the C=B bond possesses ambiphilic, multiple character. Treatment of 2 with another 1 equiv of BH3·SMe2 allows the isolation of the rare cyclic diborane species [(SCS)B2H5][Li(OEt2)] 4. The electronic structures of both compounds were investigated by means of DFT calculations. Compound 4 is an efficient catalyst for the reduction of CO2 to methanol derivatives by BH3·SMe2. A TON of ca. 2800 (TOF = 127 h-1) was achieved using 0.1 mol % of 4 in THF.
- Lafage, Mathieu,Pujol, Anthony,Saffon-Merceron, Nathalie,Mézailles, Nicolas
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p. 3030 - 3035
(2016/07/06)
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- Formation of a zwitterionic boronium species from the reaction of a stable carbenoid with borane: CO2 reduction
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The treatment of Li2C(PPh2NMes)2 (1, Mes = 2,4,6-Me3C6H2) with hexachloroethane yielded the corresponding carbenoid 2 in good yields. The reactivity of 2 was studied with BH3·SMe2 to give a zwitterionic boronium species 4, also a stable carbenoid. Both carbenoid species were found to be excellent catalysts for the CO2 reduction by BH3·SMe2. This journal is
- Ho, Samuel Y.-F.,So, Cheuk-Wai,Saffon-Merceron, Nathalie,Mzailles, Nicolas
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supporting information
p. 2107 - 2110
(2015/02/05)
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- Dehydrogenation of ammonia-borane by cationic Pd(ii) and Ni(ii) complexes in a nitromethane medium: Hydrogen release and spent fuel characterization
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A highly electrophilic cationic PdII complex, [Pd(MeCN)4][BF4]2 (1), brings about the preferential activation of the B-H bond in ammonia-borane (NH3·BH3, AB). At room temperature, the reaction between 1 in CH3NO2 and AB in tetraglyme leads to Pd nanoparticles and formation of spent fuels of the general formula MeNHxBOy as reaction byproducts, while 2 equiv. of H2 is efficiently released per AB equiv. at room temperature within 60 seconds. For a mechanistic understanding of dehydrogenation by 1, the chemical structures of spent fuels were intensely characterized by a series of analyses such as elemental analysis (EA), X-ray photoelectron spectroscopy (XPS), solid state magic-angle-spinning (MAS) NMR spectra (2H, 13C, 15N, and 11B), and cross polarization (CP) MAS methods. During AB dehydrogenation, the involvement of MeNO2 in the spent fuels showed that the mechanism of dehydrogenation catalyzed by 1 is different from that found in the previously reported results. This AB dehydrogenation derived from MeNO2 is supported by a subsequent digestion experiment of the AB spent fuel: B(OMe)3 and N-methylhydroxylamine ([Me(OH)N]2CH2), which are formed by the methanolysis of the AB spent fuel (MeNHxBOy), were identified by means of 11B NMR and single crystal structural analysis, respectively. A similar catalytic behavior was also observed in the AB dehydrogenation catalyzed by a nickel catalyst, [Ni(MeCN)6][BF4]2 (2).
- Kim, Sung-Kwan,Hong, Sung-Ahn,Son, Ho-Jin,Han, Won-Sik,Michalak, Artur,Hwang, Son-Jong,Kang, Sang Ook
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supporting information
p. 7373 - 7381
(2015/04/27)
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- Pincer-ligated nickel hydridoborate complexes: The dormant species in catalytic reduction of carbon dioxide with boranes
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Nickel pincer complexes of the type [2,6-(R2PO) 2C6H3]NiH (R = tBu, 1a; R = iPr, 1b; R = cPe, 1c) react with BH3·THF to produce borohydride complexes [2,6-(R2/su
- Chakraborty, Sumit,Zhang, Jie,Patel, Yogi J.,Krause, Jeanette A.,Guan, Hairong
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- Synthesis and characterisation of the unsubstituted dipyrrin and 4,4-dichloro-4-bora-3a,4a-diaza-s-indacene: Improved synthesis and functionalisation of the simplest BODIPY framework
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An improved and scalable synthesis of the unsubstituted 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene framework facilitates access to the previously unreported parent dipyrrin HCl salt, as well as 4,4-dichloro-4-bora- 3a,4a-diaza-s-indacene.
- Groves, Brandon R.,Crawford, Sarah M.,Lundrigan, Travis,Matta, Chérif F.,Sowlati-Hashjin, Shahin,Thompson, Alison
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supporting information
p. 816 - 818
(2013/02/23)
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- Total synthesis of gelsemoxonine
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The first total synthesis of gelsemoxonine (1) has been accomplished. Divinylcyclopropane-cycloheptadiene rearrangement of the highly functionalized substrate was successfully applied to assemble the spiro-quaternary carbon center connected to the bicyclic seven-membered core structure. A one-pot isomerization reaction of the α,β-unsaturated aldehyde to the saturated ester via the TMSCN-DBU reagent combination allowed a facile diastereoselective introduction of the latent nitrogen functionality of the unique azetidine moiety.
- Shimokawa, Jun,Harada, Takaaki,Yokoshima, Satoshi,Fukuyama, Tohru
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supporting information; experimental part
p. 17634 - 17637
(2011/12/16)
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- A spirocyclic borate and a dihydroborate derived from the 1,2-diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion [1,2-(1,2-C 2B10H10)Se2]2-: Structures, NMR spectroscopy, and DFT calculations
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The reaction of the diselenolato-1,2-dicarba-closo-dodecaborane(12) dianion with BF3-OEt2 affords selectively a spirocyclic bis(1,2-dicarba-closo-dodecaborane-1,2-diselena)borate, whereas the analogous reaction with boron trichloride leads mainly to 1,2-bis(ethylseleno)-1,2- dicarba-closo-dodecaborane(12) through ether cleavage. The spirocyclic borate reacts with methanol by cleavage of both Se-B and Se-C bonds. With borane in THF (BH3/THF) and also with LiBH4 exchange reactions take place, which afford the 1,2-dicarba-closo-dodecaborane-1,2- diselenadihydroborate. The molecular structures of both borates as tetrabutylammonium salts were determined by X-ray analysis. In solution, the borates were characterized by multinuclear magnetic resonance spectroscopy (1H, 11B, 13C, 77Se). The gas-phase geometries of the borate anions were optimized [RB3LYP/6-3111+G(d,p) level of theory], and the NMR spectroscopic parameters (chemical shifts and coupling constants) were calculated.
- Wrackmeyer, Bernd,Klimkina, Elena V.,Milius, Wolfgang
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p. 2164 - 2171
(2011/06/26)
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- Polymer-incarcerated gold-palladium nanoclusters with boron on carbon: A mild and efficient catalyst for the sequential aerobic oxidation-Michael addition of 1,3-dicarbonyl compounds to allylic alcohols
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We have developed a polymer-incarcerated bimetallic Au-Pd nanocluster and boron as a catalyst for the sequential oxidation-addition reaction of 1,3-dicarbonyl compounds with allylic alcohols. The desired tandem reaction products were obtained in good to excellent yields under mild conditions with broad substrate scope. In the course of our studies, we discovered that the excess reducing agent, sodium borohydride, reacts with the polymer backbone to generate an immobilized tetravalent boron catalyst for the Michael reaction. In addition, we found bimetallic Au-Pd nanoclusters to be particularly effective for the aerobic oxidation of allylic alcohols under base- and water-free conditions. The ability to conduct the reaction under relatively neutral and anhydrous conditions proved to be key in maintaining good catalyst activity during recovery and reuse of the catalyst. Structural characterization (STEM, EDS, SEM, and N2 absorption/desorption isotherm) of the newly prepared PI/CB-Au/Pd/B was performed and compared to PI/CB-Au/Pd. We found that while boron was important for the Michael addition reaction, it was found to alter the structural profile of the polymer-carbon black composite material to negatively affect the allylic oxidation reaction.
- Yoo, Woo-Jin,Miyamura, Hiroyuki,Kobayashi, Shu
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p. 3095 - 3103
(2011/04/25)
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- METHODS OF PURIFYING 1,2,4-BUTANETRIOL AND COMPOSITIONS INCLUDING 1,2,4-BUTANETRIOL
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Methods of purifying BT are disclosed. The method comprises adding at least one polyhydroxyl compound to a crude BT mixture comprising BT and at least one boron-containing compound to form a polyhydroxyl compound/BT mixture. In one embodiment, the polyhydroxyl compound/BT mixture is then heated to a temperature greater than the boiling point of BT but less than the boiling point of the at least one polyhydroxyl compound. In another embodiment, the polyhydroxyl compound/BT mixture is heated to a temperature greater than the melting point of the polyhydroxyl compound, and then to a temperature greater than the boiling point of BT but less than the boiling point of the at least one polyhydroxyl compound. A composition comprising BT is also disclosed.
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Page/Page column 3-4
(2011/06/10)
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- Substitution reactions at tetracoordinate boron: Synthesis of N-heterocyclic carbene boranes with boron-heteroatom bonds
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Boryl halide, carboxylate and sulfonate complexes of 1,3-bis(2,6- diisopropylphenyl)imidazol-2-ylidene (dipp-Imd-BH2X, X = halide or sulfonate) have been prepared from the parent borane dipp-Imd-BH3 by (1) substitution reactions with R-X (X = halide or sulfonate), (2) reactions with electrophiles (like I2 or NIS), or (3) acid/base reactions with HX (provided that HX has a pKa of about 2 or less). Dipp-Imd-BH 2I is most conveniently prepared by reaction with diiodine while dipp-Imd-BH2OTf is best prepared by reaction with triflic acid. These and other less reactive complexes behave as electrophiles and can be substituted by a wide range of heteroatom nucleophiles including halides, thiolates and other sulfur-based nucleophiles, isocyanate, azide, nitrite, and cyanide. The resulting products are remarkably stable, and many have been characterized by X-ray crystallography. Several are members of very rare classes of functionalized boron compounds (boron azide, nitro compound, nitrous ester, etc.).
- Solovyev, Andrey,Chu, Qianli,Geib, Steven J.,Fensterbank, Louis,Malacria, Max,Lacote, Emmanuel,Curran, Dennis P.
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supporting information; experimental part
p. 15072 - 15080
(2011/01/10)
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- Infrared and Raman spectra of trimethoxyborane isotopomers and quantum-chemical studies of structure and force field
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Infrared and Raman spectra in the gas phase are reported for trimethoxyborane, B(OCH3)3, and its 13C3 and d9 isotopomers. Some liquid phase Raman data were also obtained. Quantum-chemical (QC) studies of structure and force field have been made with B3LYP and MP2 models. These studies highlight the change in configuration of the methyl groups with change in basis set, within the C3h point group. Scaled QC force fields together with the new spectra enable assignments of fundamental bands to be improved. A Fermi resonance involving ν12 is examined. The difference in strength between the two types of C-H bond in each methyl group is reckoned to be rather less than that deduced earlier from IR spectra of B(OCHD2)3. This conclusion is supported by QC data for dimethylether. MP2 estimates of certain interaction force constants are superior to those from B3LYP calculations. Abnormal scale factors for the torsional motion involving the O-B-O-C system identify deficiencies in the QC models employed.
- Coats, Alison M.,McKean, Donald C.,Edwards, Howell G.M.,Fawcett, Victor A.
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p. 360 - 370
(2010/08/21)
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- Role of catechol in the radical reduction of B-alkylcatecholboranes in presence of methanol
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Mechanistic investigations on the previously reported reduction of B-alkylcatecholboranes in the presence of methanol led to the disclosure of a new mechanism involving catechol as a reducing agent. More than just revising the mechanism of this reaction, we disclose here the surprising role of catechol, a chain breaking antioxidant, which becomes a source of hydrogen atoms in an efficient radical chain process.
- Povie, Guillaume,Villa, Giorgio,Ford, Leigh,Pozzi, Davide,Schiesser, Carl H.,Renaud, Philippe
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supporting information; scheme or table
p. 803 - 805
(2010/06/12)
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- Catalyst-free alcoholysis of phosphane-boranes: a smooth, cheap, and efficient deprotection procedure
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Catalyst-free alcoholytic deprotection of borane-protected phosphorus compounds offers a smooth, efficient, and clean alternative to existing deprotection methods. In this paper we report our results on the general applicability of deprotecting phosphane-
- Van Overschelde, Michel,Vervecken, Elias,Modha, Sachin G.,Cogen, Simon,Van der Eycken, Erik,Van der Eycken, Johan
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experimental part
p. 6410 - 6415
(2009/12/09)
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- PYRIDINE BORANE COMPLEXES
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The present invention relates to new borane complexes with substituted pyridines, a process for the synthesis of new borane complexes with substituted pyridines, solutions comprising new borane complexes with substituted pyridines and a method of using new borane complexes with substituted pyridines for organic reactions.
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Page/Page column 3; 5
(2008/06/13)
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- Polyfluoroorganoboron-oxygen compounds. 4 [1] lithium pentafluorophenyltrimethoxyborate, Li[C6F5B(OMe) 3], reactions with selected electrophiles and nucleophiles
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Li[C6F5B(OMe)3] (1a) reacted with the electrophiles CD3C(O)CD3, CH3OD, CD 3CN, CH3CN, HOC2H4OH, Br 2, and I2 to give C6F5X (X = D, H, Br, I). The treatment of 1a with Me3SiCl or BF3 in CH 2Cl2 and CCl3F or pentene resulted in C 6F5B(OMe)2 or C6F5BF 2, respectively. The attempted metathesis of 1a with KF or [Bu 4N]Br in CH2Cl2 led to a mixture of M[(C 6F5)2B(OMe)2] (2b,c, main product) and M[C6F5B(OMe)3] (1b,c, minor product) (M = [Bu4N], K). Even in the presence of diethyl ether, THF, DME, or TMEDA salt 1a underwent dismutation to the diarylborate salt [Li(L) n][(C6F5)2B(OMe)2] (L = Et2O, THF, DME, TMEDA) and [Li(L)n][B(OMe)4]. In subsequent reactions with aqueous K[HF2] or [Bu 4N][HF2] M[(C6F5) 2B(OMe)2] (M = K, [Bu4N], [Li(L)n]) yielded K[(C6F5)2BF2] (4c) or [Bu4N][(C6F5)2BF2] (4b). The molecular structure of [Li·TMEDA][(C6F5) 2B(OMe)2] from single crystals showed significant cation-oxygen interactions.
- Adonin, Nicolay Yu.,Bardin, Vadim V.,Floerke, Ulrich,Frohn, Hermann-Josef
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p. 2638 - 2646
(2008/10/09)
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- Method of treating stroke
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The present invention provides a method of treating stroke in a patient comprising administering to said patient an effective amount of a compound of the formula: or a pharmaceutically acceptable salt thereof.
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- Recycle of discharged sodium borate fuel
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The present invention relates to an improvement in the recovery of boron values from a mixture of alkali metal borate and alkali metal hydroxide representing discharged fuel from a hydrogen generator apparatus. The mixture is reacted with carbon dioxide and a lower alcohol to form trialkyl borate, alkali bicarbonate and water. A porous water-absorbing material is added to the reaction mixture to absorb water as it forms thereby improving the yield of trialkyl borate. The trialkyl borate is converted to alkali borohydride that is used in the fuel.
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Page column 6
(2008/06/13)
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- Convergent synthesis of alpha -aryl- beta -ketonitriles
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The present invention relates to processes for the production of alpha -aryl- beta -ketonitriles, which serve as synthetic intermediates in the preparation of a series of biologically important molecules such as corticotropin releasing factor (CRF) receptor antagonists.
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- Practical and efficient procedure for the in situ preparation of B-alkoxyoxazaborolidines. Enantioselective reduction of prochiral ketones
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A new method for the in situ elaboration of B-alkoxyoxazaborolidines is presented. Their use in the enantioselective reduction of prochiral aromatic ketones provides excellent chemical and optical yields of chiral alcohols.
- Ponzo, Viviana L.,Kaufman, Teodoro S.
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p. 495 - 496
(2007/10/03)
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- Planar boron heterocycles with nucleic acid-like hydrogen-bonding motifs
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To promote the development of boron-containing purine analogues that exist in planar, non-zwitterionic dominant structural form. in aqueous solution, rigorous solution and solid state structural analyses of 1-hydroxy-1H-2,3,1-benzoxazaborine (1), 1,2-dihydro-1-hydroxy-2,3,1-benzodiazabo (2), and related 2,3,1-benzodiheteraborines were undertaken. With the aid of isotope-enriched compounds, a multisolvent 1H, 13C, 11B, and 15N NMR spectroscopic analysis of 1 and 2 was conducted, providing structurally-diagnostic chemical shift data for all non-oxygen atoms that constitute their heterocyclic peripheries. In addition, single-crystal X-ray diffraction analyses of 1 and 2 were performed. In stark contrast to their 2,4,1 isomeric counterparts, the 2,3,1-benzoxaza- and benzodiazaborines exist in planar structural form in protic solution and in the solid state and display proton dissociative and associative tendencies reflective of the predominant Bronsted, yet still Lewis acidic-capable character of the B-OH group together with the basic one at the C4-N3 imine group. In the solid state, 1 and 2 display intermolecular hydrogen-bonding patterns not too dissimilar from the motifs of certain natural nucleic acid bases. Diazaborine 2 was shown by VT-NMR to undergo a triple hydrogen-bonding solution association with a 2',3',5'-tri-O-protected cytidine in a demonstration of one biomimetic potential held by a 1-hydroxy-2,3,1-diheteraborine periphery. In general, 1, 2, and related 1-hydroxy-2,3,1-benzodiheteraborine heterocycles were found to be characterized by an environment-dependent O1 → N3 Bronsted prototropy and B-OH group Bronsted/Lewis acid ambidency so sensitive and subtle that certain past difficulties encountered in attempts to delineate their physicochemical properties now become readily appreciated.
- Groziak, Michael P.,Chen, Liya,Yi, Lin,Robinson, Paul D.
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p. 7817 - 7826
(2007/10/03)
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- Hydroboration with haloborane/trialkylsilane mixtures
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Trialkylsilanes or dialkylsilanes react rapidly with boron trichloride in the absence of ethereal solvents or other nucleophiles to form unsolvated dichloroborane. If no substrate is present, dichloroborane disproportionates to trichloroborane and two geo
- Soundararajan, Raman,Matteson, Donald S.
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p. 4157 - 4166
(2008/10/09)
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- Contributions to the Chemistry of Boron, 229. A Deceiving X-ray Single-Crystal Structure Determination: Amino-Hydrogen Exchange in Amino-alkynylboranes and ab initio Investigations of Alkynylboranes, Borirenes, and Boraallenes
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Dimeric(dimethylamino)(phenylethynyl)borane (2)2 is formed by the reaction of bis(dimethylamino)(phenylethynyl)borane (1) with 9-BBN-H.An X-ray single-crystal diffraction study revealed a central B2N2 four-membered ring for (2)2 with both alkynyl groups pointing to the same side in a cisoid arrangement.However, solution and solid-state NMR as well as ab initio calculations on model compounds show that the cis arrangement in the crystal chosen for X-ray diffraction is not representative of the bulk material, which consists of both cis and trans isomers.Further investigations of the competition between hydrogen-amino group exchange and hydroboration in the reaction of amino-alkynylboranes with hydroborating agents (9-BBN-H and catB-H) show the exchange to be much faster even in the presence of Wilkinson's catalyst and with cyclic amino-alkynylboranes such as 1,3-dimethyl-2--1,3,2-diazaborolidine (3).Ab initio calculations on alkynylboranes I, borirenes II, and boraallenes III, which are all geometrical isomeres, show alkynylboranes to be the most stable isomers only if strongly ?-donating groups X (X = NH2, F) are attached to the boron atom.In any case, boraallenes are highest in energy. - Keywords: Alkynylboranes; Borirenes; Boraallenes; Calculations, ab initio; Hydroboration
- Metzler, Nils,Noeth, Heinrich
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p. 711 - 718
(2007/10/03)
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- Coumarin derivatives, process for their preparation, their use and thiazolyl acetic acid derivatives as intermediates
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Coumarin deviatives of the formula STR1 in which R1 denotes cyano, R2 represents phenyl or thiazolyl bonded in the 2-, 4-, or 5-position, R3 denotes hydrogen, C1 -C4 -alkyl or C1 -C4 -alkoxycarbonyl-C1 -C4 -alkyl and R4 represents hydrogen, C1 -C4 -alkyl or phenylsulphonyl, where C1 -C4 -alkyl can be substituted by hydroxyl, amino, carboxyl or C1 -C4 -alkoxy-carbonyl and phenyl can be monosubstituted or disubstituted by chlorine, bromine or C1 -C4 -alkyl, where furthermore R3 and R4, together with the N atom which they substitute, can denote a morpholine ring, a piperazine ring or a triazole ring which can carry one or two substituents from the group comprising methyl, ethyl and phenyl, and where furthermore one of the radicals R2, R3 and R4 denotes or carries a primary or secondary amino group, the hydroxyl group, the carboxyl group or the C1 -C4 -alkoxy-carbonyl group or can be converted into such a group by hydrolysis or hydrogenation, are suitable for dyeing biologically active compounds.
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- Dialkylamino- and alkoxytrialkylstannanes as reagent for synthesis of organoboryl (trialkylsilyl) ketenes
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Dialkylamino- and alkoxytrialkylstannanes have been studied as N- and O-nucleophilic reagents in substitution reactions at the B-Br bond.The previously unknown bis(dialkylamino)- and dialkoxyboryl trialkylsilyl ketenes were synthesized.Some peculiarities of the reactivity of these compounds have been studied. - Key words: dialkylaminotrialkylstannane, alkoxytrialkylstannane, synthesis; borylsilyl ketene, methanolysis, aminolysis.
- Nikolaeva, S. N.,Zolotareva, A. S.,Ponomarev, S. V.,Petrosyan, V. S.
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p. 857 - 861
(2007/10/02)
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- Organoboranes. 56. Systematic study of the reactions of 1-alkenylboronic esters with representative organolithium and grignard reagents to provide an efficient, selective synthesis of organyl-1-alkenylborinic esters
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A selective reaction of the ate complexes formed with 1-alkenylboronic esters and organolithium or Grignard reagents, by treatment with either Br?nsted or Lewis acids at -78 °C to give the corresponding organylalkenylborinic esters, is explored in this study. This systematic, detailed study reveals that the nature of the alkoxy group on boron, the nature and the amount of the alkyllithium or Grignard reagent used, the solvent, the reaction temperature, and the nature and amount of the acid used all play significant roles in influencing both the yield and the selectivity achieved for the formation of the desired organylalkenylborinates. Optimized procedures for the syntheses of representative organylalkenylborinic esters in high yield are summarized.
- Brown, Herbert C.,Vasumathi, Nagarajan,Joshi, Navalkishore N.
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p. 1058 - 1067
(2008/10/08)
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- Preparation of phenylalkyl ethers and phenyl esters from benzenediazonium tetrafluoroborate with alkoxytrimethylsilanes and trimethylsilyl esters
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Sonication assisted reaction of benzenediazonium tetrafluoroborate with alkoxytrimethylsilanes and trimethylsilyl esters gives phenylalkyl ethers and phenyl esters, respectively, with trialkyl(aryl) borates as byproducts. The scope of the reaction, experimental conditions and proposed mechanism are discussed.
- Olah,Wu
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p. 204 - 206
(2007/10/02)
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- Reactions of the diboron tetrahalides B2Cl4 and B2Br4 with B5H9: Preparation and properties of the (dihaloboryl)pentaborane derivatives 1-BX2B5H8, (X = Br, Cl, F, OCH3, t-Bu, H) and synthesis of (BCl2)3B5H6
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The reactions of B2Cl4 with excess B5H9 yield 1-BCl2B5H8 (73%) while those of B2Br4 generate 1-BBr2B5H8 (80%). Ligand exchange of 1-BCl2B5H8 with excess BBr3 forms 1-BBr2B5H8 (86%), that with Hg(CF3)2 results in 1-BF2B5H8 (96%), that with CH3OH generates 1-B(OCH3)2B5H8 (46%), and that with Li(t-Bu) prepares B(t-Bu)(Cl)B5H8 (23%) and B(t-Bu)2B5H8 (20%). The relative thermal stabilities of these products are BF2B5H8 > BCl2B5H8 > BBr2B5H8 > B(OCH3)2B5H8 > B(t-Bu)2B5H8. All of these BX2B5H8 compounds (X = F, Cl, OCH3, t-Bu) decompose to form BX3 and B5H9 as the volatile products. Reactions of BCl2B5H8 with excess B2Cl4 yield (BCl2)3B5H6, a compound of limited thermal stability, but no evidence for further BCl2 substitution on the pentaborane cage was obtained. Reductions of BCl2B5H8 with LiBH4 in C6H5Cl or C6H4Cl2 form apparent equilibrium mixtures of 1:1′,2′-[B5H8][B2H5] and 1:1′-[B5H8][B2H5]. One or both of these compounds decompose with the evolution of B2H6, B5H9, and coupled pentaborane cages (B5H7)n, where n can be at least as large as 8. The 11B NMR and mass spectrometric evidence from the last reaction is consistent with the initial dimerization of the hexaborane 1-BH2B5H8, which is rapidly followed by the formation of 1:1′-[B5H8][B2H5], the cross product arising from the interaction of B2H6 with (BH2B5H8)2, and then isomerization of this heptaborane to 1:1′,2′-[B5H8][B2H5].
- Saulys,Morrison
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p. 4174 - 4179
(2008/10/08)
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- Gas-Phase Lewis Acid-Base Interactions. An Experimental Determination of Cyanide Binding Energies from Ion Cyclotron Resonance and High-Pressure Mass Spectrometric Equilibrium Measurements
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Both ion cyclotron resonance and high-pressure mass spectrometric equilibrium techniques have been used to investigate the binding energies of anions to a variety of Lewis acids.From an analysis of the enthalpy changes associated with CN- binding it is evident that in cases of relatively weak binding considerable freedom of rotational motion of CN- in the complex may be retained.Ab initio calculations and experiment suggest that binding through both the N and C sites of CN- is nearly equally favorable in some cases.In contrast to results previously obtained for Bronsted acids which showed that CN- and Cl- bind nearly identically, the present data for Lewis acids show many cases where cyanide is much more favorably bound than chloride, a consequence of enhanced covalent binding of the CN- complexes.New Kroeger Drago parameters derived for CN- support the importance of covalent binding in cyanide adducts.Correlations of binding energy of anions to Lewis acids with the anion proton affinity show excellent linear relationships which may be used to predict binding energetics for new anions.
- Larson, J. W.,Szulejko, J. E.,McMahon, T. B.
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p. 7604 - 7609
(2007/10/02)
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- Cage-expansion and -contraction reactions of nido-6-SB9H11: Improved synthetic routes to nido-7-SB10H12 and arachno-4-SB8H12
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Improved synthetic routes have been developed for the preparation of nido-7-SB10H12 and arachno-4-SB8H12. Good yields (>60%) of nido-7-SB10H12 can be obtained by acidification of the anion that is formed either by the reaction of nido-6-SB9H11 with NaBH4 under reflux conditions or by the reaction of nido-SB9H10- with BH3·THF. arachno-4-SB8H12 can be obtained in moderate yields (～20%) either by oxidative degradation of the arachno-SB9H12- anion or by base degradation of arachno-9-L-6-SB9H11 (L = Et2S or Et3N).
- Kang, Sang Ook,Sneddon, Larry G.
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p. 3298 - 3300
(2008/10/08)
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- Chemical behavior and structure of triply bridged pyrazaboles of the type RB(μ-pz)2(μ-OBRO)BR
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Triply bridged pyrazaboles of the type RB(μ-pz)2(μ-OBRO)BR (1, R = C2H5, C6H5; Hpz = pyrazole) are thermally quite stable and can be sublimed without decomposition even under atmospheric pressure. At room temperature they are resistant to water but are not soluble. Dissolution of 1 in protonic solvents occurs with complete breakdown of the molecule. Halogenation of 1 (R = C2H5) with SOCl2 yields the pyrazabole RClB(μ-pz)2BRCl. The latter compound is a valuable material for the preparation of various other pyrazaboles. Thus, reaction with alkali-metal alkoxide or with alcohol in the presence of triethylamine gives access to R(R′O)B(μ-pz)2BR(OR′) (R′ = CH3, C2H5), the first examples of B-alkoxypyrazaboles; with (CX3CO)2O (X = H, F), the species with R′ = CX3CO are obtained. The crystal and molecular structures of 1 with R = C2H5 were determined. The molecule crystallizes in the monoclinic system in space group P21/c with a = 7.587 (2) A?, b = 12.415 (2) A?, c = 16.387 (3) A?, β = 90.50 (2)°, and Z = 4.
- Hsu,Mariategui,Niedenzu,Shore
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p. 143 - 147
(2008/10/08)
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- DERIVES MONO ET BICYCLIQUES DU BORE TETRACOORDONNE ET DES α-AMINODIACIDES: REACTIONS AVEC DIVERS NUCLEOPHILES
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Water, methanol and isopropylamine react mono- and bi-cyclic boroxazolidones (2a and 3a) by attacking the boron atom and not the CO group, with formation of aminodiacid and tricoordinated boron compounds.The boron compounds undergo successive B-C cleavage
- Garrigues, Bernard,Mulliez, Michel
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-
- Addition compounds of alkali-metal hydrides. 24. A general method for preparation of potassium trialkoxyborohydrides. A new class of reducing agents
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The generality of the synthesis of potassium triisopropoxyborohydride, stabilized toward disproportionation by storing over excess potassium hydride, was examined with seven additional organoborates of varying steric requirements. The reaction of trimethoxy- and triethoxyborane with potassium hydride proceeded readily at room temperature, but the products could not be stabilized by the presence of excess potassium hydride. Triphenoxyborane reacted readily, even at -10°C, and stabilization was achieved. Tri-sec-butoxy- and tricyclopentoxyborane required refluxing in THF for 12-24 h, and the products were stabilized over potassium hydride. Finally, the reactions of tris(2-methylcyclohexoxy)- and tri-tert-butoxyborane were even slower, requiring a number of days for completion. Both products were stabilized toward disproportionation over potassium hydride. Indeed, potassium tri-tert-butoxyborohydride was quite stable toward disproportionation without excess potassium hydride. The stereoselectivities of these reagents in the reduction of representative cyclic ketones were examined. The stereoselectivities varied in an erratic manner with the steric requirements of the alkoxy group and did not approach the stereoselectivities previously achieved with lithium tri-sec-butylborohydride and lithium trisiamylborohydride.
- Brown, Herbert C.,Cha, Jin Soon,Nazer, Behrooz
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p. 2929 - 2931
(2008/10/08)
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