NaBHEt3 Research Articles

Mechanism of Silylation of Vinyl Arenes by Hydrodisiloxanes Driven by Stoichiometric Amounts of Sodium Triethylborohydride-A Combined DFT and Experimental Study.

The reactions of vinyl arenes with hydrodisiloxanes in the presence of sodium triethylborohydride were studied using experimental and computational methods. The expected hydrosilylation products were not detected because triethylborohydrides did not exhibit the catalytic activity observed in previous studies; instead, the product of formal silylation with dimethylsilane was identified, and triethylborohydride was consumed in stoichiometric amounts. In this article, the mechanism of the reaction is described in detail, with due consideration given to the conformational freedom of important intermediates and the two-dimensional curvature of the potential energy hypersurface cross sections. A simple way to reestablish the catalytic character of the transformation was identified and explained with reference to its mechanism. The reaction presented here is an example of the application of a simple transition-metal-free catalyst in the synthesis of silylation products, with flammable gaseous reagents replaced by a more convenient silane surrogate.

Hydroboration of alkynes initiated by sodium triethylborohydride

Sodium triethylborohydride, a popular hydride transferring reagent, is commonly used as an activating agent for hydroboration catalysts based on the first-row transition metal complexes. It has been found that NaHBEt3 can be a selective catalyst for hydroboration of terminal alkynes with pinacolborane. Hydroboration of aromatic and aliphatic alkynes in the presence of 10 mol% of NaHBEt3 proceeded in a highly selective manner to give (E)-vinylboronate esters with high yields, whereas ethynylsilanes seem to be less reactive in this process. Internal alkynes can also be transformed into corresponding vinylboronate esters, however, this process require prolonged reaction times compared to their terminal counterparts.

Synthesis of Quinolino[1,2-c]quinazolin-6-one Derivatives via Formal (4+2)-Cycloaddition of Alkenes to Quinazolinе-Derived N-Acyliminium Cations: An Experimental and Theoretical Study

Abstract3-Aryl-4-hydroxy-1-methyl-3,4-dihydroquinazolin-2(1H)-ones were synthesized by reduction of 3-aryl-1-methylquinazoline-2,4(1H,3H)-diones with sodium triethylborohydride and studied as precursors of N-acyliminium cations that were expected to be trapped with various alkenes as (4+2)-cycloadducts. Unsubstituted 3-aryl-4-hydroxy-1-methyl-3,4-dihydroquinazolin-2(1H)-ones in the presence of BF3·Et2O failed to produce the desired cycloadducts probably due to a homooligomerization reaction involving N-acyliminium intermediates. To prevent this side reaction, we found it necessary to introduce substituents at both positions C6 and C8 of the quinazoline ring and C4′ of the 3-phenyl substituent. Utilizing bromine atoms as substituents at C6 and C8, N-acyliminium cations generated from 3-aryl-6,8-dibromo-4-hydroxy-1-methyl-3,4-dihydroquinazolin-2(1H)-ones in the presence of BF3·Et2O smoothly reacted with such alkenes as indene, acenaphthylene, styrene, α-methylstyrene to give new quinolino[1,2-c]quinazolin-6-one derivatives with high regio- and stereoselectivity. Density functional theory calculations were performed at the M06-2x/cc-pVDZ level to obtain an insight into the mechanism of the (4+2)-cycloaddition reaction of quinazoline-derived N-acyliminium cations to alkenes.

Markovnikov-selective double hydrosilylation of challenging terminal aryl alkynes under cobalt and iron catalysis.

Geminal bis(silanes) are unique compounds with interesting properties. The most straightforward way to access them is double hydrosilylation of alkynes, which was established only recently. Previous articles about transition metal-catalysed double hydrosilylation show that terminal aryl alkynes are a challenge. We report on cobalt(II) and iron(III) complexes with the easy-to-synthesise N,N,N-tridentate hydrazone ligand being active precatalysts in Markovnikov-selective double hydrosilylation of terminal aryl alkynes. The influence of the hydrazone ligand structure and the potential role of the sodium triethylborohydride activator were studied. Sets of geminal bis(silanes) with two identical or different silyl groups were synthesised, showing the applicability of the reported method.

An Anionic Ruthenium Dihydride [Cp*(iPr2MeP)RuH2]− and Its Conversion to Heterobimetallic Ru(μ-H)2M (M = Ir or Cu) Complexes

A novel dihydridoruthenate, [(solv)Na][Cp*(iPr2MeP)RuH2] (2; solv = THF or OEt2), was synthesized from Cp*(iPr2MeP)RuCl (1) and sodium triethylborohydride. Compound 2 was used to generate “Cp*(iPr2MeP)RuH” equivalents by salt metathesis with 1, which resonance Raman spectroscopy indicates is a mixture of the terminal dinitrogen complex, Cp*(iPr2MeP)RuH(N2) (4), and diastereomers of the bridging dinitrogen complex [Cp*(iPr2MeP)RuH]2(μ-N2) (meso, 5, and a pair of enantiomers, 6). Compound 2 also reacted with the late transition metal chloride complexes [(COD)IrCl]2 and (IPr)CuCl [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] to form hydride-bridged heterobimetallic complexes Cp*(iPr2MeP)Ru(μ-H)2Ir(COD) (7) and Cp*(iPr2MeP)Ru(μ-H)2Cu(IPr) (8), respectively, that feature weakened Ru–H interactions relative to those of 2.

Sodium triethylborohydride as a catalyst for the dehydrogenative silylation of terminal alkynes with hydrosilanes.

The first example of sodium triethylborohydride-catalyzed C(sp)-H bond silylation is reported. The reaction of aromatic and aliphatic alkynes with aromatic hydrosilanes and hydrosiloxanes proceeded in a highly selective manner to afford dehydrocoupling products. Competitive hydrosilylation of the terminal alkyne did not occur as a side-reaction. In view of the above it is remarkable that NaHBEt3 is commonly used as a reducing agent generating active transition-metal catalysts in situ in other hydrosilylation reactions.

Unexpected catalytic activity of simple triethylborohydrides in the hydrosilylation of alkenes.

The first example of sodium triethylborohydride-catalysed hydrosilylation of alkenes is reported. The hydrosilylation of certain alkenes, in particular styrenes, vinylsilanes and allyl glycidyl ether, with aromatic hydrosilanes proceeded in a highly regioselective manner to give Markovnikov products. It is significant that several protocols use NaHBEt3 as a reducing agent generating active catalysts in situ of other hydrosilylation reactions. An anionic mechanism of hydrosilylation is proposed.

Functionalization of Carbon Dioxide with Ethylene at Molybdenum Hydride Complexes

The molybdenum tetrahydride species (Triphos)MoH4PPh3 (Triphos = PhP(CH2CH2PPh2)2) generated from sodium triethylborohydride addition to (Triphos)MoCl3 was found to promote CO2 functionalization to afford acrylate, propionate, and formate species. The formation of (Triphos)MoH4PPh3 occurs via a (Triphos)Mo(H)Cl(PPh3) intermediate followed by dismutation of an unobserved six-coordinate molybdenum(II) dihydride complex. Addition of dihydrogen to the dismuation product mixture affords a nearly quantitative yield of (Triphos)MoH4PPh3. The molybdenum tetrahydride species facilitates CO2 insertion into a metal hydride to produce a formate complex, (Triphos)Mo(H)(κ2-CHO2)(PPh3), with an observed rate constant of [2.9(2)] × 10–4 s–1 (25 °C), which is independent of CO2 pressure. Selective formation of acrylate and propionate carbon dioxide–ethylene coupling products, (Triphos)Mo(H)(κ2-C3H3O2)(PPh3) and (Triphos)Mo(H)(κ2-C3H5O2)(PPh3), was achieved by sequential addition of olefin and heterocumulene to (Triphos)Mo...

ChemInform Abstract: Hydrosilylation of Aldehydes and Ketones Catalyzed by an N‐Heterocyclic Carbene‐Nickel Hydride Complex under Mild Conditions.

Half-sandwich N-heterocyclic carbene (NHC)-nickel complexes of the general formula [Ni(NHC)ClCp†] (Cp†=Cp, Cp*) efficiently catalyze the hydrosilylation of aldehydes and ketones at room temperature in the presence of a catalytic amount of sodium triethylborohydride and thus join the fairly exclusive club of well-defined nickel(II) catalyst precursors for the hydrosilylation of carbonyl functionalities. Of notable interest is the isolation of an intermediate nickel hydride complex that proved to be the real catalyst precursor.

Iron‐Catalysed Reduction of Olefins using a Borohydride Reagent

AbstractThe iron‐catalysed reduction of olefins has been achieved using a simple iron salt and sodium triethylborohydride. A wide range of mono‐ and trans‐1,2‐disubstituted alkenes have been reduced (91–100%) using 25 mol% iron(II) triflate, 1 mol% N‐methyl‐2‐pyrrolidinone and 4 equivalents of sodium triethylborohydride. The reduction of alkynes to alkanes is also reported (up to 84%). Significantly, the reduction of trisubstituted alkenes has also been achieved (60–86%).

Hydrosilylation of Aldehydes and Ketones Catalyzed by an N‐Heterocyclic Carbene‐Nickel Hydride Complex under Mild Conditions

AbstractHalf‐sandwich N‐heterocyclic carbene (NHC)‐nickel complexes of the general formula [Ni(NHC)ClCp†] (Cp†=Cp, Cp*) efficiently catalyze the hydrosilylation of aldehydes and ketones at room temperature in the presence of a catalytic amount of sodium triethylborohydride and thus join the fairly exclusive club of well‐defined nickel(II) catalyst precursors for the hydrosilylation of carbonyl functionalities. Of notable interest is the isolation of an intermediate nickel hydride complex that proved to be the real catalyst precursor.

Synthesis and deprotonation of (phenylselenolatodimethylsilyl)bis(trimethylsilyl) methane: The crystal structure of (Me3Si)2(Me2SiBr)CH

The moisture-sensitive compound [{bromodimethylsilyl}bis(trimethylsilyl)methane], [(Me3Si)2(Me2SiBr)CH] 1 has been synthesized by the bromination of the hydride [(Me3Si)2(Me2SiH)CH] in CCl4 in good yield. Compound 1 has been characterized by multinuclear NMR and a single crystal X-ray diffraction studies. The average Si–C and BrMe2Si–C distances are, respectively, 1.894(2) and 1.886(2) Å. The Si–C–Si angle is 114.98(13)°. Treatment of 1 with NaSePh (obtained from the sodium triethylborohydride reduction of diphenyldiselenide) in benzene at room temperature resulted in the isolation of light yellow oil, [{phenylselenatodimethylsilyl}bis(trimethylsilyl)methane], [(Me3Si)2(Me2SiSePh)CH] 2. Compound 2 has been metallated with methyllithium as well as lithium diisopropylamide (LDA) in THF to give [(Me3Si)2(Me2SiSePh)CLi·2THF] 3. Compounds 2 and 3 have been characterized by elemental analysis, mass and multinuclear NMR studies.

Synthesis of nanostructured and Ni-Cr3C2 powders by an organic solution reaction method

Nanostructured nickel/chromium (NiCr) and nickel-chromium carbide (NiCr3C2) powders were prepared via a chemical route. The technique involves reductive decomposition of an organic solution of metal chloride precursors using sodium triethylborohydride. After co-precipitation of a nanoscale mixed metal (Ni+Cr) powder, low temperature annealing is used to form nanostructured NiCr alloy powder, or low temperature gas phase carburization to form nanostructured Ni-Cr3C2 cermet powder. These powders were characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and chemical analysis. The mechanisms of halide reduction and phase formation are discussed.

ChemInform Abstract: 4,4′‐Coupled Bis(isoquinolines)

Reaction of the eneamine 1 formed in situ from isoquinoline and sodium triethylborohydride with aromatic dialdehydes 3 produces 4,4′-coupled bis(isoquinolines) 4 in good yields. These compounds are readily oxidized with manganese dioxide to the corresponding diketones 5.

4,4′‐Coupled bis(isoquinolines)

AbstractReaction of the eneamine 1 formed in situ from isoquinoline and sodium triethylborohydride with aromatic dialdehydes 3 produces 4,4′‐coupled bis(isoquinolines) 4 in good yields. These compounds are readily oxidized with manganese dioxide to the corresponding diketones 5.

Desulfurization of thiols and thioketones by sodium triethylborohydride and iron(II) chloride on alumina

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDesulfurization of thiols and thioketones by sodium triethylborohydride and iron(II) chloride on aluminaHoward Alper, Sharon Ripley, and Trish L. PrinceCite this: J. Org. Chem. 1983, 48, 2, 250–252Publication Date (Print):January 1, 1983Publication History Published online1 May 2002Published inissue 1 January 1983https://doi.org/10.1021/jo00150a020RIGHTS & PERMISSIONSArticle Views461Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Phenylberyllium hydride–trimethylamine: some observations on alkylberyllium hydrides

Phenylberyllium hydride–trimethylamine, prepared from diphenylberyllium, beryllium chloride, sodium triethylborohydride, and trimethylamine, is a dimer [(Me3N)PhBeH]2 in benzene. The analogous trimethylphosphine complex dissociates in benzene solution.The trimethylamine complex of methylberyllium hydride may be prepared from dimethylberyllium and triethylstannane in the presence of ether; alkyl–alkyl exchange does not take place. The reaction between ether-free diethylberyllium and triethylstannane results in the precipitation of hydride-rich material, in which tin compounds are held, containing Be–H: Be–Et in ratio up to ca. 7 : 1. Hydrogen is also formed in this reaction.Reaction between ethylberyllium hydride–trimethylamine and diethylmercury gives Et2BeNMe3, mercury, and ethane.