- Implications of CO2 Activation by Frustrated Lewis Pairs in the Catalytic Hydroboration of CO2: A View Using N/Si+ Frustrated Lewis Pairs
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A series of base-stabilized silylium species were synthesized and their reactivity toward CO2 explored, yielding the characterization of a novel N/Si+ FLP-CO2 adduct. These silicon species are active catalysts in the hydroboration of CO2 to the methoxide level with 9-BBN, catecholborane (catBH), and pinacolborane (pinBH). Both experiments and DFT calculations highlight the role of the FLP-CO2 adduct in the catalysis. Depending on the nature of the hydroborane reductant, two distinct mechanisms have been unveiled. While 9-BBN and catBH are able to reduce an intermediate FLP-CO2 adduct, the hydroboration of CO2 with pinBH follows a different and novel path where the B-H bond is activated by the silicon-based Lewis acid catalyst. In these mechanisms, the formation of a highly stabilized FLP-CO2 adduct is found detrimental to the kinetics of the reaction.
- Von Wolff,Lefèvre,Berthet,Thuéry,Cantat
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- CO2 Fixation and Catalytic Reduction by a Neutral Aluminum Double Bond
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CO2 fixation and reduction to value-added products is of utmost importance in the battle against rising CO2 levels in the Earth's atmosphere. An organoaluminum complex containing a formal aluminum double bond (dialumene), and thus an alkene equivalent, was used for the fixation and reduction of CO2. The CO2 fixation complex undergoes further reactivity in either the absence or presence of additional CO2, resulting in the first dialuminum carbonyl and carbonate complexes, respectively. Dialumene (1) can also be used in the catalytic reduction of CO2, providing selective formation of a formic acid equivalent via the dialuminum carbonate complex rather than a conventional aluminum–hydride-based cycle. Not only are the CO2 reduction products of interest for C1 added value products, but the organoaluminum complexes isolated represent a significant step forward in the isolation of reactive intermediates proposed in many industrially relevant catalytic processes.
- Weetman, Catherine,Bag, Prasenjit,Szilvási, Tibor,Jandl, Christian,Inoue, Shigeyoshi
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- Synthesis and characterization of rare-earth metallate amido complexes bearing the 2-amidate-functionalized indolyl ligand and their application in the hydroboration of esters with pinacolborane
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The reactions of 2-amidate-functionalized indolyl proligand 2-(2,6-iPr2C6H3NHCO)C8H5NH (H2L) with [(Me3Si)2N]3RE(μ-Cl)Li(THF)3 were studied leading to the synthesis and characterization of a series of novel discrete trinuclear rare-earth metallate amido complexes containing the anion [{η1:(μ2-η1:η1):η1-LREN(SiMe3)2}3(μ3-Cl)]? and cation Li+(THF)4 (RE = Y(1a), Nd (1b), Sm (1c), Gd (1d), Dy (1e), Er (1f), and Yb (1g)) in good yields by silylamine elimination. All of the complexes were characterized by spectroscopic methods, elemental analyses and single-crystal X-ray diffraction, and complexes 1a and 1c were additionally characterized by NMR spectroscopy. As proof of principle of their activity, these complexes were used as precatalysts for the hydroboration of esters using HBpin as the hydride source displaying high activity under neat and room temperature conditions. As a result, the ligand, ionic and multinuclear cooperative effects on catalytic activity were observed.
- Bao, Qin,Gao, Jianjian,Hong, Dongjing,Mu, Xiaolong,Song, Lulu,Wang, Shaowu,Wei, Yun,Zhou, Shuangliu,Zhu, Xiancui
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p. 2953 - 2961
(2022/02/21)
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- Hydroboration of nitriles, esters, and amides catalyzed by simple neosilyllithium
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We present here an efficient method for the hydroboration of organic nitriles, carboxylic esters, and carboxamides with pinacolborane (HBpin) using an alkali metal catalyst, neosilyllithium (LiCH2SiMe3), in neat reaction conditions. The reactions were accomplished with efficient catalytic reactivity and demonstrated by neosilyllithium at room temperature, in solvent-free condition, to afford a high yield of the corresponding N-boryl amines, boryl ethers, and amine hydrochlorides. The protocol for the catalytic reaction presented in this paper is simple and efficient, with diverse substrate scope for nitriles, carboxylic esters, and carboxamides showing excellent functional group tolerance. DLPNO-CCSD(T) calculations were also performed, showing that the hydroboration of nitriles catalyzed by neosilyllithium occurs through the pre-coordination of the nitrile at Lewis acid lithium followed by hydride migration from the B–H entity.
- Bandyopadhyay, Ayan,Bhattacharjee, Jayeeta,Kumar Singh, Saurabh,Kumari, Kusum,Moorthy, Shruti,Panda, Tarun K.,Sai Kumar, Gobbilla
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supporting information
(2022/03/31)
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- Reductive depolymerization of polyesters and polycarbonates with hydroboranes by using a lanthanum(iii) tris(amide) catalyst
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The homogeneous reductive depolymerization of polyesters and polycarbonates with hydroboranes is achieved with the use of an f-metal complex catalyst. These polymeric materials are transformed into their value-added alcohol equivalents. Catalysis proceeds readily, under mild conditions, with La[N(SiMe3)2]3 (1 mol%) and pinacolborane (HBpin) and shows high selectivity towards alcohols and diols, after hydrolysis.
- Berthet, Jean-Claude,Cantat, Thibault,Kobylarski, Marie
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supporting information
p. 2830 - 2833
(2022/03/09)
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- Catalytic Hydroboration of Esters by Versatile Thorium and Uranium Amide Complexes
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The challenging hydroboration of esters is achieved using simple uranium and thorium amides, U[N(SiMe3)2]3 and [(Me3Si)2N]2An[κ2-(N,C)-CH2Si(CH3)2N(SiMe3)] (An = Th or U) acting as precatalysts in the reaction with pinacolborane (HBpin). All three complexes showed impressive catalytic activities, reaching excellent yields. A large scope of esters was investigated including aliphatic, aromatic, and heterocyclic esters that were transformed cleanly to the corresponding hydroborated alcohols, which readily hydrolyzed to the free alcohols. Moreover, the actinide catalysts demonstrated unexpected high functional tolerance toward nitro, halide, cyano, and heteroaromatic functional groups. The reaction exhibited excellent selectivity toward the ester when additional double and triple unsaturated C-C bonds were present. Lactones and poly caprolactone have been successfully cleaved to the monomeric units, showing a great promise toward polymer degradation and recycling. Detailed kinetic studies are provided in order to determine the rate dependence on the concentration of catalyst, HBpin, and ester. A plausible mechanism is proposed based on stoichiometric reactions, DFT calculations, thermodynamic measurements, and deuterium-labeling studies.
- Makarov, Konstantin,Kaushansky, Alexander,Eisen, Moris S.
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p. 273 - 284
(2022/01/03)
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- N-Heterocyclic Carbene-Phosphinidenide Complexes as Hydroboration Catalysts
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The reactions of the N-heterocyclic carbene-phosphinidene adducts (NHC)PSiMe3 and (NHC)PH with the dinuclear ruthenium and osmium complexes [(η6-p-cymene)MCl2]2 (M = Ru, Os) afforded the half-sandwich complexes
- Bhattacharjee, Jayeeta,Bockfeld, Dirk,Tamm, Matthias
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supporting information
p. 1098 - 1109
(2022/01/27)
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- Progressing the Frustrated Lewis Pair Abilities of N-Heterocyclic Carbene/GaR3Combinations for Catalytic Hydroboration of Aldehydes and Ketones
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Exploiting the steric incompatibility of the tris(alkyl)gallium GaR3 (R = CH2SiMe3) and the bulky N-heterocyclic carbene (NHC) 1,3-bis(tert-butyl)imidazol-2-ylidene (ItBu), here we report the B-H bond activation of pinacolborane (HBPin), which has led to
- Bole, Leonie J.,Uzelac, Marina,Hernán-Gómez, Alberto,Kennedy, Alan R.,O'Hara, Charles T.,Hevia, Eva
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supporting information
p. 13784 - 13796
(2021/07/26)
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- Catalytic hydroboration of carbonyl derivatives by using phosphinimino amide ligated magnesium complexes
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Reduction of carbonyl derivatives by using Earth-abundant, cheap, and environmentally benign metal-based catalysts through an atom-efficient method is a challenging task. Herein, we report the synthesis and characterization of dinuclear magnesium complexes 1-3 chelated by a phosphinimino amide skeleton. In combination with pinacolborane (HBpin) as a reducing agent, complex 1 bearing an ortho-methyl substituent on the phenyl ring of the ligand showed excellent reduction capability for a broad range of carbonyl derivatives under mild reaction conditions. Aldehydes, ketones, and acrolein substrates were efficiently reduced to the corresponding alkoxy-borane products with a record high TOF. Besides, acrolein derivatives were exclusively reduced to 1,2-regioselective products. Using two equiv. of HBpin, ester substrates were reduced to two kinds of alkoxy-borane products. Carbonate reduction accomplished by using complex 1 and three equiv. of HBpin afforded diols and a methanol precursor, respectively. When chiral substrates such as (S)-1,2-propanediol carbonate and l-lactide or polymeric P(l-LA) were employed, the chirality was almost retained in their reductive products.
- Cui, Dongmei,Li, Min,Liu, Xinli
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supporting information
p. 13037 - 13041
(2021/10/12)
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- Readily available lithium compounds as catalysts for the hydroboration of carbodiimides and esters
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Selective and efficient hydroboration of esters and carbodiimides to alcohols and amines by two well-defined and readily accessible lithium complexes, 2,6-di-tert-butyl phenolate lithium (1a) and 1,1’-dilithioferrocene (1b) are described. A range of aliphatic, aromatic, and cyclic esters with various functional groups were selectively converted into the corresponding boronate esters. Similarly, the single hydroboration of carbodiimides with aliphatic and aromatic substituents on the nitrogen atoms was studied. A possible mechanistic pathway of the hydroboration of carbodiimides with HBpin has been proposed using NMR studies and DFT calculations. These reactions are convenient alternatives to stoichiometric hydride reduction or hydrogenation. The employing of lithium complexes is also significant, because of the need to find cheap and green alternatives to noble metal complexes.
- Bisai, Milan Kumar,Das, Tamal,Gour, Kritika,Sen, Sakya S.,Vanka, Kumar
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supporting information
(2021/06/26)
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- La(CH2C6H4NMe2-o)3-catalyzed reduction of esters to alcohols with pinacolborane
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Catalytic reduction of esters is a favourable synthetic strategy to obtain the corresponding alcohols. La(CH2C6H4NMe2-o)3, a simple and facilely accessible lanthanide complex, can serve as a highly efficient catalyst for the reduction of esters with pinacolborane (HBpin), selectively affording alcohols in good yields under mild conditions. This protocol exhibits good tolerance for many functional groups such as C-C double bond, nitro, halogen, furyl, and thienyl groups. A lanthanum hydride species like [La]-H·HBpin is supposed to play a crucial role in promoting the interaction of esters with HBpin.
- Gong, Mingliang,Luo, Yunjie,Xie, Hongzhen,Zhang, Fangcao
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supporting information
p. 17654 - 17659
(2021/10/04)
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- Palladium on carbon as an efficient, durable and economical catalyst for the alcoholysis of B2pin2
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Hydrogen has attracted much attention as one of the most promising chemical fuel candidates because of its zero emission during consumption. In order to solve the freezing problem of water based hydrolysis process, herein, the Pd/C as an efficient and stable catalyst for the methanolysis, ethanolysis, propanolysis and butanolysis of B2pin2 for the generation of hydrogen has been first developed. The large kinetic isotope effect (KIE) of kH/kD = 5.0, D2 formation from CD3OD and in situ tandem reaction have confirmed that alcohol is the only hydrogen source. Interestingly, the order of Ea of these alcohols in H2 evolution is MeOH (methanol, 29.57 kJ/mol) nBuOH (n-butanol, 41.98 kJ/mol), which is consistent with the known order of acidities of these alcohols (MeOH > EtOH > PrOH > nBuOH).
- Li, Ning,Liu, Xiang,Meng, Xu,Shen, Jialu,Zhou, Junjie
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- Hydroboration of Nitriles, Esters, and Carbonates Catalyzed by Simple Earth-Abundant Metal Triflate Salts
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During the past decade earth-abundant metals have become increasingly important in homogeneous catalysis. One of the reactions in which earth-abundant metals have found important applications is the hydroboration of unsaturated C?C and C?X bonds (X=O or N). Within these set of transformations, the hydroboration of challenging substrates such as nitriles, carbonates and esters still remain difficult and often relies on elaborate ligand designs and highly reactive catalysts (e. g., metal alkyls/hydrides). Here we report an effective methodology for the hydroboration of challenging C≡N and C=O bonds that is simple and applicable to a wide set of substrates. The methodology is based on using a manganese(II) triflate salt that, in combination with commercially available potassium tert-butoxide and pinacolborane, catalyzes the hydroboration of nitriles, carbonates, and esters at room temperature and with near quantitative yields in less than three hours. Additional studies demonstrated that other earth-abundant metal triflate salts can facilitate this reaction as well, which is further discussed in this report.
- Thenarukandiyil, Ranjeesh,Satheesh, Vanaparthi,Shimon, Linda J. W.,de Ruiter, Graham
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p. 999 - 1006
(2021/03/30)
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- Manganese-Catalyzed Hydroborations with Broad Scope
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Reductive transformations of easily available oxidized matter are at the heart of synthetic manipulation and chemical valorization. The applications of catalytic hydrofunctionalization benefit from the use of liquid reducing agents and operationally facile setups. Metal-catalyzed hydroborations provide a highly prolific platform for reductive valorizations of stable C=X electrophiles. Here, we report an especially facile, broad-scope reduction of various functions including carbonyls, carboxylates, pyridines, carbodiimides, and carbonates under very mild conditions with the inexpensive pre-catalyst Mn(hmds)2. The reaction could be successfully applied to depolymerizations.
- Ghosh, Pradip,Jacobi von Wangelin, Axel
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supporting information
p. 16035 - 16043
(2021/06/16)
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- Super hydride catalyzed ester and isocyanate hydroboration
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Commercially available, eco-friendly lithium triethylborohydride (LiHBEt3, Super hydride) was shown to be an excellent catalyst for the solvent-free hydroboration of esters using pinacolborane at ambient reaction conditions. This was achieved w
- Behera, Bedabyas,Ding, Yi,Du, Zonggang,Kumar, Arun
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supporting information
(2021/08/09)
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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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- A N-Phosphinoamidinato NHC-Diborene Catalyst for Hydroboration
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The use of the N-phosphinoamidinato NHC-diborene catalyst 2 for hydroboration is described. The N-phosphinoamidine tBu2PN(H)C(Ph)= N(2,6-iPr2C6H3) was reacted with nBuLi in Et2O to afford the lithium derivative, which was then treated with B2Br4(SMe2)2 in toluene to form the N-phosphinoamidinate-bridged diborane 1. It was reacted with the N-heterocyclic carbene IMe (:C{N(CH3)C(CH3)}2) and excess potassium graphite at room temperature in toluene to give the N-phosphinoamidinato NHC-diborene compound 2. It can stoichiometrically activate ammonia-borane and carbon dioxide. It also showed catalytic capability. A 2 mol % portion of 2 catalyzed the hydroboration of carbon dioxide (CO2) with pinacolborane (HBpin) in deuterated benzene (C6D6) at 110 °C (conversion >99%), which afforded the methoxyborane [pinBOMe] (yield 97.8%, TOF 33.3 h-1) and the bis(boryl) oxide [(pinB)2O]. In addition, 5 mol % of 2 catalyzed the N-formylation of secondary and primary amines by carbon dioxide and pinacolborane to yield the N-formamides (average yield 91.6%, TOF 25.9 h-1). Moreover, 2 showed chemoselectivity toward catalytic hydroboration of carbonyl compounds. In mechanistic studies, the B= B double bond in compound 2 activated the substrates, the intermediates of which then underwent hydroboration with pinacolborane to yield the products and regenerate catalyst 2.
- Fan, Jun,Mah, Jian-Qiang,Yang, Ming-Chung,Su, Ming-Der,So, Cheuk-Wai
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supporting information
p. 4993 - 5002
(2021/02/01)
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- Expedient Hydrofunctionalisation of Carbonyls and Imines Initiated by Phosphacyclohexadienyl Anions
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The ability of phosphacyclohexadienyl anions [Li(1-R-PC5Ph3H2)] [R=Me (1 a), nBu (1 b), tBu (1 c), Ph (1 d) and CH2SiMe3 (1 e)] to initiate hydrofunctionalisation reactions was investigated and compar
- Margeson, Matthew J.,Seeberger, Felix,Kelly, John A.,Leitl, Julia,Coburger, Peter,Szlosek, Robert,Müller, Christian,Wolf, Robert
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p. 3761 - 3764
(2021/06/25)
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- Pincer-Supported Gallium Complexes for the Catalytic Hydroboration of Aldehydes, Ketones and Carbon Dioxide
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Gallium hydrides stabilised by primary and secondary amines are scarce due to their propensity to eliminate dihydrogen. Consequently, their reactivity has received limited attention. The synthesis of two novel gallium hydride complexes HGa(THF)[ON(H)O] and H2Ga[μ2-ON(H)O]Ga[ON(H)O] ([ON(H)O]2?=N,N-bis(3,5-di-tert-butyl-2-phenoxy)amine) is described and their reactivity towards aldehydes and ketones is explored. These reactions afford alkoxide-bridged dimers through 1,2-hydrogallation reactions. The gallium hydrides can be regenerated through Ga?O/B?H metathesis from the reaction of such dimers with pinacol borane (HBpin) or 9-borabicyclo[3.3.1]nonane (9-BBN). These observations allowed us to target the catalytic reduction of carbonyl substrates (aldehydes, ketones and carbon dioxide) with low catalyst loadings at room temperature.
- Liu, Lingyu,Lo, Siu-Kwan,Smith, Cory,Goicoechea, Jose M.
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supporting information
p. 17379 - 17385
(2021/11/03)
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- Boric acid as a precatalyst for BH3-catalyzed hydroboration
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We report that boric acid, BO3H3, is a good precatalyst for the BH3-catalyzed hydroboration of esters using pinacolborane as a borylation agent. Using microwave irradiation as an energy source, we demonstrated that a dozen esters were converted into the c
- Fontaine, Frédéric-Georges,Légaré Lavergne, Julien,To, Hoang-Minh
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p. 31941 - 31949
(2021/12/01)
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- Hydroboration of aldehydes, ketones and CO2under mild conditions mediated by iron(iii) salen complexes
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The hydroboration of aldehydes, ketones and CO2is demonstrated using a cheap and air stable [Fe(salen)]2-μ-oxo pre-catalyst with pinacolborane (HBpin) as the reductant under mild conditions. This catalyst system chemoselectively hydroborates aldehydes over ketones and ketones over alkenes. In addition, the [Fe(salen)2]-μ-oxo pre-catalyst shows good efficacy at reducing “wet” CO2with HBpin at room temperature.
- James, Alexander P.,Lau, Samantha,Provis-Evans, Cei B.,Webster, Ruth L.
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supporting information
p. 10696 - 10700
(2021/08/17)
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- Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes
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A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]?- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle.
- Tian, Ya-Ming,Guo, Xiao-Ning,Krummenacher, Ivo,Wu, Zhu,Nitsch, J?rn,Braunschweig, Holger,Radius, Udo,Marder, Todd B.
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supporting information
p. 18231 - 18242
(2020/11/02)
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- Mild catalytic deoxygenation of amides promoted by thorium metallocene
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The organoactinide-catalyzed (Cp*2ThMe2) hydroborated reduction of a wide range of tertiary, secondary, and primary amides to the corresponding amines/amine-borane adductsviadeoxygenation of the amides is reported herein. The catalytic reactions proceed under mild conditions with low catalyst loading and pinacolborane (HBpin) concentration in a selective fashion. Cp*2ThMe2is capable of efficiently catalysing the gram-scale reaction without a drop in efficiency. The amine-borane adducts are successfully converted into free amine products in high conversions, which increases the usefulness of this catalytic system. A plausible mechanism is proposed based on detailed kinetics, stoichiometric, and deuterium labeling studies.
- Eisen, Moris S.,Saha, Sayantani
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supporting information
p. 12835 - 12841
(2020/10/05)
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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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- Magnesium-catalyzed hydroboration of organic carbonates, carbon dioxide and esters
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A low-valent magnesium(i) complex [(XylNacnac)Mg]2 was employed as a highly efficient precatalyst for the hydroboration of a variety of cyclic and linear organic carbonates, polycarbonates, CO2 and esters with HBpin under mild conditions. The resultant boronates can be used for the preparation of the corresponding value-added diols, triols or alcohols through hydrolysis.
- Cao, Xu,Lu, Kai,Ma, Mengtao,Wang, Weifan,Xue, Fei,Yao, Weiwei
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supporting information
p. 2776 - 2780
(2020/03/13)
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- Hydroboration reaction method of carbonic ester
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The invention relates to a hydroboration reaction method of carbonic ester, in particular to a hydroboration reaction method taking carbonic ester and borane as raw materials. As an important non-metallocene ligand, beta-ketimine is easy to synthesize; th
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Paragraph 0009; 0026
(2020/10/21)
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- Dialumenes-aryl: Vs. silyl stabilisation for small molecule activation and catalysis
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Main group multiple bonds have proven their ability to act as transition metal mimics in the last few decades. However, catalytic application of these species is still in its infancy. Herein we report the second neutral NHC-stabilised dialumene species by use of a supporting aryl ligand (3). Different to the trans-planar silyl-substituted dialumene (3Si), compound 3 features a trans-bent and twisted geometry. The differences between the two dialumenes are explored computationally (using B3LYP-D3/6-311G(d)) as well as experimentally. A high influence of the ligand's steric demand on the structural motif is revealed, giving rise to enhanced reactivity of 3 enabled by a higher flexibility in addition to different polarisation of the aluminium centres. As such, facile activation of dihydrogen is now achievable. The influence of ligand choice is further implicated in two different catalytic reactions; not only is the aryl-stabilised dialumene more catalytically active but the resulting product distributions also differ, thus indicating the likelihood of alternate mechanisms simply through a change of supporting ligand.
- Bag, Prasenjit,Hanusch, Franziska,Inoue, Shigeyoshi,Porzelt, Amelie,Weetman, Catherine
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p. 4817 - 4827
(2020/06/17)
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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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- La[N(SiMe3)2]3-Catalyzed Hydroboration of Esters and Other Challenging Unsaturated Groups
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The commercially available homoleptic lanthanum amide La[N(SiMe3)2]3 (LaNTMS) is reported to enable the hydroboration of esters using pinacolborane (HBpin) as the reducing agent. A wide range of substrates inclu
- Kang, Zihan,Xu, Xiaojuan,Xue, Mingqiang,Yan, Dandan
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p. 1142 - 1146
(2019/10/22)
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- Application of amine trisilicate rare earth complex in catalysis of reaction of carbonic ester and boron hydride
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The invention discloses application of an amine trisilicate rare earth complex in catalysis of reaction of a carbonic ester and borane. The application includes: in the condition of nitrogen and the existence of the amine trisilicate rare earth complex, e
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Paragraph 0027
(2019/10/04)
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- Hydroboration method for organic carbonate
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The invention discloses a hydroboration method for organic carbonate, and belongs to the technical field of organic matter synthesis. The method comprises the following steps: adding a beta-diimine monovalent magnesium compound into a mixture of pinacolborane and organic carbonate; stirring and reacting at room temperature. According to the hydroboration method for the organic carbonate disclosedby the invention, the activity of the beta-diimine monovalent magnesium compound serving as a catalyst for catalyzing the organic carbonate and the pinacolborane is high; the substrate universality iswide; the reaction catalytic efficiency is high; the product yield is high; the hydroboration method for the organic carbonate has very high practicability.
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Paragraph 0082-0087
(2019/08/20)
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- Reduction of Cyclic and Linear Organic Carbonates Using a Readily Available Magnesium Catalyst
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Efficient reduction of cyclic and linear organic carbonates catalyzed by a readily available earth alkaline catalyst has been achieved. The described homogenous reaction based on a ligand-free magnesium catalyst provides an indirect route for the conversion of CO2 into valuable alcohols. The reaction proceeds with high yields under mild reaction conditions, with low catalyst loading and short reaction times, and shows a broad applicability toward various linear and cyclic carbonates. Additionally, it can be applied for the depolymerization of polycarbonates.
- Szewczyk, Marcin,Magre, Marc,Zubar, Viktoriia,Rueping, Magnus
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p. 11634 - 11639
(2019/12/02)
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- La[N(SiMe3)2]3-Catalyzed Ester Reductions with Pinacolborane: Scope and Mechanism of Ester Cleavage
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Tris[N,N-bis(trimethylsilyl)amido]lanthanum (LaNTMS) is an efficient, highly active, and selective homogeneous catalyst for ester reduction with pinacolborane (HBpin). Alkyl and aryl esters are cleaved to the corresponding alkoxy- and aryloxy-boronic esters which can then be straightforwardly hydrolyzed to alcohols. Ester reduction is achieved with 1 mol % catalyst loading at 25-60 °C, and most substrates are quantitatively reduced in 1 h. Nitro, halide, and amino functional groups are well tolerated, and ester reduction is completely chemoselective over potentially competing intra- or intermolecular alkene or alkyne hydroboration. Kinetic studies, isotopic labeling, and density functional theory calculations with energetic span analysis argue that ester reduction proceeds through a rate-determining hydride-transfer step that is ligand-centered (hydride is transferred directly from bound HBpin to bound ester) and not through a metal hydride-based intermediate that is often observed in organolanthanide catalysis. The active catalyst is proposed to be a La-hemiacetal, [(Me3Si)2N]2La-OCHR(OR)[HBpin], generated in situ from LaNTMS via hydroboronolysis of a single La-N(SiMe3)2 bond. These results add to the growing compendium of selective oxygenate transformations that LaNTMS is competent to catalyze, further underscoring the value and versatility of homoleptic lanthanide complexes in homogeneous catalytic organic synthesis.
- Barger, Christopher J.,Motta, Alessandro,Weidner, Victoria L.,Lohr, Tracy L.,Marks, Tobin J.
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p. 9015 - 9024
(2019/10/02)
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- Selective Hydroboration of Carboxylic Acids with a Homogeneous Manganese Catalyst
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Catalytic reduction of carboxylic acid to the corresponding alcohol is a challenging task of great importance for the production of a variety of value-added chemicals. Herein, a manganese-catalyzed chemoselective hydroboration of carboxylic acids has been developed with a high turnover number (>99?000) and turnover frequency (>2000 h-1) at 25 °C. This method displayed tolerance of electronically and sterically differentiated substrates with high chemoselectivity. Importantly, aliphatic long-chain fatty acids, including biomass-derived compounds, can efficiently be reduced. Mechanistic studies revealed that the reaction occurs through the formation of active manganese-hydride species via an insertion and bond metathesis type mechanism.
- Barman, Milan K.,Das, Kuhali,Maji, Biplab
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p. 1570 - 1579
(2019/01/30)
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- Cobalt catalysed reduction of CO2via hydroboration
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We report an operationally convenient reduction of CO2 to methanol via cobalt catalysed hydroboration which occurs under mild reaction conditions. Addition of NaHBEt3 to Co(acac)3 generates an active hydroboration catalyst, which is proposed to be a “Co-H” species on the basis of infrared spectroscopy. The reduction of CO2 in the presence of various boranes showed that BH3·SMe2 afforded near quantitative conversion (98% NMR yield) to methanol upon hydrolysis.
- Tamang, Sem Raj,Findlater, Michael
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supporting information
p. 8199 - 8203
(2018/07/10)
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- Efficient Reduction of Carbon Dioxide to Methanol Equivalents Catalyzed by Two-Coordinate Amido-Germanium(II) and -Tin(II) Hydride Complexes
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The bulky amido-germanium(II) and -tin(II) hydride complexes, L?EH [E = Ge or Sn; L? = -N(Ar?) (SiPri3); Ar? = C6H2Pri{C(H)Ph2}2-4,2,6
- Hadlington, Terrance J.,Kefalidis, Christos E.,Maron, Laurent,Jones, Cameron
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p. 1853 - 1859
(2017/03/20)
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- Zinc hydridotriphenylborates supported by a neutral macrocyclic polyamine
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The zinc hydridotriphenylborates [(L)Zn(TMDS)][HBPh3] and [(L)ZnX][HBPh3] (L = Me4TACD, Me4[12]aneN4; TMDS = N(SiHMe2)2; X = Cl, Br, I) were synthesized by BPh3-mediated β-SiH abstraction and salt metathesis with KHBPh3, respectively. CO2 is rapidly inserted into the B-H bonds. [(L)Zn(TMDS)][HBPh3] catalyzes the hydroboration of polar substrates including CO2.
- Mukherjee, Debabrata,Wiegand, Ann-Kristin,Spaniol, Thomas P.,Okuda, Jun
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supporting information
p. 6183 - 6186
(2017/07/11)
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- Generation of Hydrogen from Water: A Pd-Catalyzed Reduction of Water Using Diboron Reagent at Ambient Conditions
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Production of hydrogen from renewable sources, particularly from water, is an intensive area of research, which has far-reaching relevance in hydrogen economy. A homogeneous catalytic method is presented for producing clean hydrogen gas from water, in a reaction of water with a diboron compound as the reductant, under ambient reaction conditions. The Pd-catalytic system is stable in water and displays excellent recyclability. Hydroxy analogues such as alcohols are compatible with the Pd/B2Pin2 system and generate hydrogen gas efficiently. The B2Pin2-H2O system, in the presence of palladium, is an excellent catalytic system for selective hydrogenation of olefins.
- Ojha, Devi Prasan,Gadde, Karthik,Prabhu, Kandikere Ramaiah
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p. 5062 - 5065
(2016/10/14)
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- Catalytic Use of Elemental Gallium for Carbon-Carbon Bond Formation
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The first catalytic use of Ga(0) in organic synthesis has been developed by using a Ag(I) cocatalyst, crownether ligation, and ultrasonic activation. Ga(I)-catalyzed C-C bond formations between allyl or allenyl boronic esters and acetals, ketals, or aminals have proceeded in high yields with essentially complete regio- and chemoselectivity. NMR spectroscopic analyses have revealed novel transient Ga(I) catalytic species, formed in situ through partial oxidation of Ga(0) and B-Ga transmetalation, respectively. The possibility of asymmetric Ga(I) catalysis has been demonstrated.
- Qin, Bo,Schneider, Uwe
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supporting information
p. 13119 - 13122
(2016/10/25)
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- Insertion of CO2 into the carbon-boron bond of a boronic ester ligand
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New Ru and Zn diazafluorenyl complexes undergo C-H borylation of the diazafluorenyl ligand to form the corresponding diazafluorenylboronic ester complexes, which can insert CO2 into their C-B bonds to form boryl ester functionalities. The relev
- Janes, Trevor,Osten, Kimberly M.,Pantaleo, Adam,Yan, Ellen,Yang, Yanxin,Song, Datong
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supporting information
p. 4148 - 4151
(2016/03/19)
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- Magnesium hydridotriphenylborate [Mg(thf)6][HBPh3]2: A versatile hydroboration catalyst
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Magnesium bis(hydridotriphenylborate), isolated as a solvent-separated ion pair [Mg(thf)6][HBPh3]2, effectively catalyzed the hydroboration of several unsaturated substrates including CO2.
- Mukherjee, Debabrata,Shirase, Satoru,Spaniol, Thomas P.,Mashima, Kazushi,Okuda, Jun
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supporting information
p. 13155 - 13158
(2016/11/09)
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- Iron-catalyzed reduction of CO2 into methylene: Formation of C-N, C-O, and C-C bonds
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We report herein the use of the (dihydrido)iron catalyst, Fe(H)2(dmpe)2, for the selective reduction of CO2 into either bis(boryl)acetal or methoxyborane depending on the hydroborane used as a reductant. In a one-pot two-step procedure, the in situ generated bis(boryl)acetal was shown to be a reactive and versatile source of methylene to create new C-N but also C-O and C-C bonds.
- Jin, Guanghua,Werncke, C. Gunnar,Escudié, Yannick,Sabo-Etienne, Sylviane,Bontemps, Sébastien
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supporting information
p. 9563 - 9566
(2015/08/18)
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- Organocatalysts with carbon-centered activity for CO2 reduction with boranes
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We report two organocatalysts for CO2 hydroboration to methylborylethers, which upon hydrolysis can produce methanol. These organocatalysts feature carbon-centered reversible CO2 binding, broad borane scopes, and high catalytic activities.
- Yang, Yanxin,Xu, Maotong,Song, Datong
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supporting information
p. 11293 - 11296
(2015/07/07)
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- Aromaticity as stabilizing element in the bidentate activation for the catalytic reduction of carbon dioxide
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A new transition-metal-free mode for the catalytic reduction of carbon dioxide via bidentate interaction has been developed. In the presence of Li2[1,2-C6H4(BH3)2], CO2 can be selectively transformed to either methane or methanol, depending on the reducing agent. The bidentate nature of binding is supported by X-ray analysis of an intermediate analogue, which experiences special stabilization due to aromatic character in the bidentate interaction. Kinetic studies revealed a first-order reaction rate. The transformation can be conducted without any solvent.
- Lu, Zhenpin,Hausmann, Heike,Becker, Sabine,Wegner, Hermann A.
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p. 5332 - 5335
(2015/05/13)
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- Cooperative bond activation and catalytic reduction of carbon dioxide at a group 13 metal center
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A single-component ambiphilic system capable of the cooperative activation of protic, hydridic and apolar H-X bonds across a Group 13 metal/activated β-diketiminato (Nacnac) ligand framework is reported. The hydride complex derived from the activation of H2 is shown to be a competent catalyst for the highly selective reduction of CO2 to a methanol derivative. To our knowledge, this process represents the first example of a reduction process of this type catalyzed by a molecular gallium complex. A single-component ambiphilic Group 13 system has been developed, capable of the cooperative activation of protic, hydridic, and apolar H-X bonds. The hydride complex derived from the activation of H2 catalyzes the selective transformation of CO2 to a methanol derivative, representing the first example of such a reduction process catalyzed by a molecular gallium complex.
- Abdalla, Joseph A. B.,Riddlestone, Ian M.,Tirfoin, Rémi,Aldridge, Simon
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supporting information
p. 5098 - 5102
(2015/04/27)
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- Conversion of Carbon Dioxide to Methanol Using a C-H Activated Bis(imino)pyridine Molybdenum Hydroboration Catalyst
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Using a multistep synthetic pathway, a bis(imino)pyridine (or pyridine diimine, PDI) molybdenum catalyst for the selective conversion of carbon dioxide into methanol has been developed. Starting from (Ph2PPrPDI)Mo(CO), I2 addition af
- Pal, Raja,Groy, Thomas L.,Trovitch, Ryan J.
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p. 7506 - 7515
(2015/08/11)
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- Ruthenium-catalyzed reduction of carbon dioxide to formaldehyde
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Functionalization of CO2 is a challenging goal and precedents exist for the generation of HCOOH, CO, CH3OH, and CH4 in mild conditions. In this series, CH2O, a very reactive molecule, remains an elementary C1 building block to be observed. Herein we report the direct observation of free formaldehyde from the borane reduction of CO2 catalyzed by a polyhydride ruthenium complex. Guided by mechanistic studies, we disclose the selective trapping of formaldehyde by in situ condensation with a primary amine into the corresponding imine in very mild conditions. Subsequent hydrolysis into amine and a formalin solution demonstrates for the first time that CO2 can be used as a C 1 feedstock to produce formaldehyde.
- Bontemps, Sébastien,Vendier, Laure,Sabo-Etienne, Sylviane
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supporting information
p. 4419 - 4425
(2014/04/03)
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- Carbene-9-BBN ring expansions as a route to intramolecular frustrated lewis pairs for CO2 reduction
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Reactions of phosphine-derived carbenes with 9-borabicyclo[3.3.1]nonane (9-BBN) result in ring-expansion reactions to generate novel intramolecular frustrated Lewis pairs (FLPs). These FLPs effect the catalytic reduction of CO2 in the presence of boranes to give BOB and methoxy-borate species. A BOB well done: Reactions of phosphine-derived carbenes with 9-borabicyclo[3.3.1]nonane (9-BBN) result in ring-expansion reactions to generate novel intramolecular frustrated Lewis pairs (FLPs). These FLPs effect the catalytic reduction of CO2 in the presence of boranes to give BOB and methoxy-borate species (see scheme).
- Wang, Tongen,Stephan, Douglas W.
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supporting information
p. 3036 - 3039
(2014/03/21)
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- Synthesis and reactivity of a masked PSiP pincer supported nickel hydride
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Tridentate PSiP pincer ligands featuring two phosphine donors and an anionic Si donor have attracted considerable attention in recent years. Here, we report the synthesis of the η3-cyclooctenyl complex, (PhPSiP)Ni(η3-cyclooctenyl) (1; PhPSiP = Si(Me)(2-PPh2-C6H4)2) through the reaction of Ni(COD)2 with PhPSiHP (PhPSiHP = HSi(Me)(2-PPh2-C6H4)2). We propose, that as a result of β-hydride elimination of 1,3-COD, 1 can act as a synthetic equivalent for (PhPSiP)NiH. The reaction of 1 with a variety of different reagents including another equivalent of PhPSiHP to form (PhPSiP)2Ni (2), 1,3-COD and H2, PPh3 to form the Ni(0) species (PhPSiHP)Ni(PPh3) (3) and 1,3-COD and 2,6-lutidine·HCl to generate (PhPSiP)NiCl (4), 1,3-COD and H2 are in agreement with this hypothesis. In addition, in the reaction of 1 with BH3·THF, (PhPSiP)Ni(κ2-BH4) (5) was observed but could not be isolated. This reaction presumably proceeds via (PhPSiP)NiH. This is supported by the observation that the reaction of (CyPSiP)NiH (CyPSiP = Si(Me)(2-PCy2-C6H4)2) with BH3·THF formed (CyPSiP)Ni(κ2-BH4) (6). Catalytic reactions such as alkene isomerization and CO2 reduction using 1 as precatalyst are also consistent with a nickel hydride being accessible. Compounds 1, 2 and 6 were characterized by X-ray crystallography.
- Suh, Hee-Won,Guard, Louise M.,Hazari, Nilay
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supporting information
p. 37 - 43
(2015/02/19)
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- Trapping formaldehyde in the homogeneous catalytic reduction of carbon dioxide
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Formaldehyde detectives: Evidence for the production of formaldehyde during a ruthenium-catalyzed CO2 reduction process, and for its involvement in the formation of the resulting C2 compound, is disclosed. Ultimately, formaldehyde can be recovered by methanol trapping. HBPin=pinacolborane. Copyright
- Bontemps, Sebastien,Sabo-Etienne, Sylviane
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supporting information
p. 10253 - 10255
(2013/10/21)
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