- Hydrodechlorination of Et3NBCl3 catalyzed by amorphous nickel boride - A mechanistic approach
-
The catalytic hydrodechlorination of BCl3 with molecular hydrogen in the presence of tertiary amines is a viable strategy for the energy-efficient generation of valuable B-H bonds. A mechanistic study based on experiments with isolated intermediates and deuterium labeling experiments is presented. The occurrence of the rate-limiting reverse reaction from the insoluble Et3NHCl adduct was identified as a major cause of low Et3NBH3 yields. In addition, amines with NCH2 units, which also serve in the corresponding cases as solvents, have a strong influence on the reaction kinetics; they are directly involved in the hydrogen transfer at elevated temperatures and assume the role of a cocatalyst. A catalytic cycle for the reaction on a nickel boride catalyst is proposed. Copyright
- Reller, Christian,Mertens, Florian O.R.L.
-
-
Read Online
- One-pot synthesis of ammonia-borane and trialkylamine-boranes from trimethyl borate
-
A one-pot procedure for the preparation of ammonia borane from trimethyl borate in 90% yield and >99% purity has been reported. This methodology has been modified to prepare a series of trialkylamine-boranes in 70-82% yields from trimethyl borate and lithium hydride/aluminum chloride in the presence of the corresponding trialkylamine.
- Veeraraghavan Ramachandran,Raju, Bhimapaka C.,Gagare, Pravin D.
-
-
Read Online
- The quest for silylhydroboranes: (Me3Si)3SiBH 2
-
Reaction of BH3.NEt3 with tris(trimethylsilyl) silylpotassium yielded the respective silylboranate. Abstraction of a hydride with B(C6F5)3 led to the neutral silylborane, which could be derivatised as an Et3N adduct. Treatment of the boranate with Cp2Ti(btmsa) resulted in exchange of THF coordinating to potassium by Cp2Ti(btmsa). The Royal Society of Chemistry.
- Arp, Henning,Marschner, Christoph,Baumgartner, Judith
-
-
Read Online
- Lanthanide(lll) and actinide(lll) complexes [M(BH4) 2(THF)5][BPh4] and [M(BH4) 2(18-crown-6)][BPh4] (M = Nd, Ce, U): synthesis, crystal structure, and density functional theory i
-
Treatment of [M(BH4)3(THF)3] with NEt 3HBPh3 in THF afforded the cationic complexes [M(BH 4)2(THF)5][BPh4] [M = U (1), Nd (2), Ce (3)] which were transforme
- Arliguie, Therese,Belkhiri, Lotfi,Bouaoud, Salah-Eddine,Thuery, Pierre,Villiers, Claude,Boucekkine, Abdou,Ephritikhine, Michel
-
-
Read Online
- Activation of sodium borohydride via carbonyl reduction for the synthesis of amine- And phosphine-boranes
-
A highly versatile synthesis of amine-boranes via carbonyl reduction by sodium borohydride is described. Unlike the prior bicarbonate-mediated protocol, which proceeds via a salt metathesis reaction, the carbon dioxide-mediated synthesis proceeds via reduction to a monoformatoborohydride intermediate. This has been verified by spectroscopic analysis, and by using aldehydes and ketones as the carbonyl source for the activation of sodium borohydride. This process has been used to produce borane complexes with 1°-, 2°-, and 3°-amines, including those with borane reactive functionalities, heteroarylamines, and a series of phosphines.
- Hamann, Henry J.,Lin, Randy,Veeraraghavan Ramachandran, P.
-
supporting information
p. 16770 - 16774
(2021/12/08)
-
- Photoinduced Single-Electron Transfer as an Enabling Principle in the Radical Borylation of Alkenes with NHC–Borane
-
A photoinduced SET process enables the direct B?H bond activation of NHC–boranes. In contrast to common hydrogen atom transfer (HAT) strategies, this photoinduced reaction simply takes advantage of the beneficial redox potentials of NHC–boranes, thus obviating the need for extra radical initiators. The resulting NHC–boryl radical was used for the borylation of a wide range of α-trifluoromethylalkenes and alkenes with diverse electronic and structural features, providing facile access to highly functionalized borylated molecules. Labeling and photoquenching experiments provide insight into the mechanism of this photoinduced SET pathway.
- Chen, Xiao-Qing,Hu, Yuan-Zhuo,Song, Dan,Xia, Peng-Ju,Xiang, Hao-Yue,Xiao, Jun-An,Yang, Hua,Ye, Zhi-Peng
-
supporting information
p. 6706 - 6710
(2020/02/05)
-
- Photocatalytic C-F Bond Borylation of Polyfluoroarenes with NHC-boranes
-
The first photoredox-catalyzed defluoroborylation of polyfluoroarenes with NHC-BH3 has been facilely achieved at room temperature via a single-electron-transfer (SET)/radical addition pathway. This new strategy makes full use of the advantage of photoredox catalysis to generate the key boryl radical via direct activation of a B-H bond. Good functional group tolerance and high regioselectivity offer this protocol incomparable advantages in preparing a wide array of valuable polyfluoroarylboron compounds. Moreover, both computational and experimental studies were performed to illustrate the reaction mechanism.
- Chen, Kai,Chen, Xiao-Qing,Hu, Yuan-Zhuo,Xia, Peng-Ju,Xiang, Hao-Yue,Xiao, Jun-An,Yang, Hua,Ye, Zhi-Peng
-
supporting information
p. 1742 - 1747
(2020/03/24)
-
- AMINE-BORANES BEARING BORANE-INTOLERANT FUNCTIONALITIES
-
Disclosed herein is the preparation of functional group containing amine-boranes from the corresponding amines. The mild reaction conditions allow for the direct preparation of several hitherto inaccessible amine-boranes containing a functional moiety, such as but not limited to, alkene, alkyne, hydroxyl, thiol, acetal, ester, amide, nitrile, nitro, and alkoxysilane.
- -
-
Paragraph 0053; 0054; 0055
(2018/03/10)
-
- The role of ammonia in promoting ammonia borane synthesis
-
Ammonia promotes the synthesis of pure ammonia borane (AB) in excellent yields from sodium borohydride and ammonium sulfate in tetrahydrofuran under ambient conditions. An examination of the influence of added ammonia reveals that it is incorporated into the product AB, contrary to its perceived function as a catalyst or a co-solvent. Mechanistic studies point to a nucleophilic attack by ammonia on ammonium borohydride with concurrent dehydrogenation to yield AB.
- Ramachandran, P. Veeraraghavan,Kulkarni, Ameya S.
-
p. 16433 - 16440
(2016/10/31)
-
- Open-Flask Synthesis of Amine-Boranes via Tandem Amine-Ammonium Salt Equilibration-Metathesis
-
An amine-ammonium salt equilibration-metathesis sequence provides high-purity amine-boranes in excellent yields from sodium borohydride in refluxing reagent-grade tetrahydrofuran in an open flask.
- Ramachandran, P. Veeraraghavan,Kulkarni, Ameya S.
-
supporting information
p. 5618 - 5620
(2015/06/25)
-
- Reductive dechlorination of BCl3 for efficient ammonia borane regeneration
-
This paper reports a complete ammonia borane (AB) regeneration process in which Bu3SnH was utilized as a reductant for the reductive dechlorination of BCl3, and Et2PhN was selected as a 'helper ligand' to generate Et2PhN·BH3, which gives rise to a high yield of AB by a base-exchange reaction at ambient temperature.
- Tan, Yingbin,Zhang, Lijun,Chen, Xiaowei,Yu, Xuebin
-
supporting information
p. 753 - 757
(2015/02/19)
-
- Rhodium(I)-catalyzed asymmetric carbene insertion into B-H bonds: Highly enantioselective access to functionalized organoboranes
-
A unique rhodium(I)-catalyzed asymmetric B-H insertion of α-diazo carbonyl compounds with easily available amine-borane adducts was achieved using a newly developed C1-symmetric chiral diene as ligand. This first Rh(I)-carbene-directed B-H insertion example represents an attractive and promising approach for synthesis of highly enantioenriched organoboron compounds, allowing for the efficient construction of α-boryl esters and ketones with excellent enantioselectivities (up to 99% ee) under exceptionally mild conditions.
- Chen, Diao,Zhang, Xu,Qi, Wei-Yi,Xu, Bin,Xu, Ming-Hua
-
supporting information
p. 5268 - 5271
(2015/05/13)
-
- Hydrodechlorination of Et3NBCl3 catalyzed by amorphous nickel boride - A mechanistic approach
-
The catalytic hydrodechlorination of BCl3 with molecular hydrogen in the presence of tertiary amines is a viable strategy for the energy-efficient generation of valuable B-H bonds. A mechanistic study based on experiments with isolated intermediates and deuterium labeling experiments is presented. The occurrence of the rate-limiting reverse reaction from the insoluble Et3NHCl adduct was identified as a major cause of low Et3NBH3 yields. In addition, amines with NCH2 units, which also serve in the corresponding cases as solvents, have a strong influence on the reaction kinetics; they are directly involved in the hydrogen transfer at elevated temperatures and assume the role of a cocatalyst. A catalytic cycle for the reaction on a nickel boride catalyst is proposed. The mechanistic aspects of the generation of borane species from BCl3 by catalytic hydrodechlorination with molecular hydrogen in the presence of tertiary amines are investigated. The NCH2 units of the amines are particularly important to the overall reaction kinetics and these units are assigned the role of cocatalyst. Equilibrium investigations guide the way for the improvement of the synthesis.
- Reller, Christian,Mertens, Florian O. R. L.
-
p. 450 - 459
(2015/04/27)
-
- Nucleophilic displacement of ammonia from ammonia borane for the preparation of alkylamine-, pyridine- and phosphine-boranes
-
A near quantitative and safe preparation of a series of aliphatic amine- and phosphine-boranes from ammonia borane (AB) in refluxing THF has been achieved by exploiting the volatility of ammonia. A one-pot preparation of lithium aminoborohydrides from AB has also been described.
- Veeraraghavan Ramachandran,Kulkarni, Ameya S.
-
p. 26207 - 26210
(2014/07/08)
-
- Amine-Boranes: Green hypergolic fuels with consistently low ignition delays
-
Complexation of amines with borane converts them to hypergols or decreases their ignition delays (IDs) multifold (with white fuming nitric acid as the oxidant). With consistently low IDs, amine-boranes represent a class of compounds that can be promising alternatives to toxic hydrazine and its derivatives as propellants. A structure-hypergolicity relationship study reveals the necessary features for the low ID.
- Veeraraghavan Ramachandran,Kulkarni, Ameya S.,Pfeil, Mark A.,Dennis, Jacob D.,Willits, Jared D.,Heister, Stephen D.,Son, Steven F.,Pourpoint, Timothee L.
-
supporting information
p. 16869 - 16872
(2015/01/09)
-
- Electrophilic C-H borylation and related reactions of B-H boron cations
-
Catalytic procedures are described for the amine-directed borylation of aliphatic and aromatic tertiary amine-boranes. Sequential double borylation is observed in cases where two or more C-H bonds are available that allow 5-center or 6-center intramolecular borylation. The HNTf2-catalyzed borylation of benzylamine-boranes provides a practical means for the synthesis of ortho-substituted arylboronic acid derivatives, suitable for Suzuki-Miyaura cross-coupling applications.
- Prokofjevs, Aleksandrs,Jermaks, Janis,Borovika, Alina,Kampf, Jeff W.,Vedejs, Edwin
-
p. 6701 - 6711
(2014/01/06)
-
- Pincer-ligated nickel hydridoborate complexes: The dormant species in catalytic reduction of carbon dioxide with boranes
-
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
-
-
- A self-contained regeneration scheme for spent ammonia borane based on the catalytic hydrodechlorination of BCl3
-
Recycling: A self-contained procedure for the recycling of BNH-waste, based on the three major steps: polymer break-up, amine supported catalytic hydrodehalogenation of boron halogens, and the base exchange in borane amine adducts, is developed (see picture). Beyond the original task of recycling spent ammonia borane, the process provides a new means to produce borohydride species efficiently, by the direct use of molecular hydrogen. Copyright
- Reller, Christian,Mertens, Florian O.R.L.
-
p. 11731 - 11735
(2013/01/15)
-
- Lithium aminoborohydrides 17. Palladium catalyzed borylation of aryl iodides, bromides, and triflates with diisopropylaminoborane prepared from lithium diisopropylaminoborohydride
-
The Alcaraz-Vaultier borylation of aryl halides and triflates is reported utilizing diisopropylaminoborane (BH2N(iPr)2) prepared from the corresponding lithium aminoborohydride (LAB reagent). BH 2N(iPr)2, prepared by reacting lithium diisopropylaminoborohydride with trimethylsilyl chloride, provided the most consistent isolated yields from this reaction. Catalytic amounts of palladium dichloride produced the highest yields from aryl iodides, while catalytic tris(dibenzylideneacetone)dipalladium(chloroform) provided the best yields for aryl bromides and triflates. This route to boronic acids is mild enough to tolerate various functionalities and for the first time employs aryl triflates as substrates for the Alcaraz-Vaultier borylation. In addition, it was found that both boronic acid and ester compounds could be isolated from the reaction mixture utilizing simple work-up procedures. Treatment of the reaction intermediate with an acid/base work-up provided the corresponding boronic acid, while treating the same intermediate with a diol, such as neopentyl glycol, afforded the corresponding boronic ester.
- Haddenham, Dustin,Bailey, Christopher L.,Vu, Chau,Nepomuceno, Gabby,Eagon, Scott,Pasumansky, Lubov,Singaram, Bakthan
-
scheme or table
p. 576 - 583
(2011/03/18)
-
- Synthesis of amine boranes
-
A method for preparing an amine borane from an alkali metal borohydride and an amine salt. The alkali metal borohydride is allowed to react with 0.95 to 1.05 equivalents of the amine salt in a solvent which contains water and an amine.
- -
-
Page/Page column 3; 5
(2010/06/14)
-
- Thermodynamic studies and hydride transfer reactions from a rhodium complex to BX3 compounds
-
This study examines the use of transition-metal hydride complexes that can be generated by the heterolytic cleavage of H2 gas to form B-H bonds. Specifically, these studies are focused on providing a reliable and quantitative method for determining when hydride transfer from transition-metal hydrides to three-coordinate BX3 (X = OR, SPh, F, H; R = Ph, p-C 6H4OMe, C6F5, tBu, Si(Me)3) compounds will be favorable. This involves both experimental and theoretical determinations of hydride transfer abilities. Thermodynamic hydride donor abilities (ΔG°H-) were determined for HRh(dmpe)2 and HRh(depe)2, where dmpe ) 1,2-bis(dimethylphosphinoethane) and depe ) 1,2-bis(diethylphosphinoethane), on a previously established scale in acetonitrile. This hydride donor ability was used to determine the hydride donor ability of [HBEt3]- on this scale. Isodesmic reactions between [HBEt3]- and selected BX3 compounds to form BEt3 and [HBX3]- were examined computationally to determine their relative hydride affinities. The use of these scales of hydride donor abilities and hydride affinities for transition-metal hydrides and BX3 compounds is illustrated with a few selected reactions relevant to the regeneration of ammonia borane. Our findings indicate that it is possible to form B-H bonds from B-X bonds, and the extent to which BX3 compounds are reduced by transition-metal hydride complexes forming species containing multiple B-H bonds depends on the heterolytic B-X bond energy. An example is the reduction of B(SPh)3 using HRh(dmpe)2 in the presence of triethylamine to form Et 3N-BH3 in high yields.
- Mock, Michael T.,Potter, Robert G.,Camaioni, Donald M.,Li, Jun,Dougherty, William G.,Kassel, W. Scott,Twamley, Brendan,DuBois, Daniel L.
-
experimental part
p. 14454 - 14465
(2010/02/16)
-
- Electrophilic activation of Lewis base complexes of borane with trityl tetrakis(pentafluorophenyl)borate
-
Borenium ions do not accumulate under the conditions of hydride abstraction from Lewis base borane complexes (L·BH3) using trityl cation because subsequent rapid reaction with L·BH3 occurs to form B - H - B bonds. The hydride-bridged
- De Vries, Timothy S.,Vedejs, Edwin
-
p. 3079 - 3081
(2008/10/09)
-
- Stabilization of pentaborane(9) toward air oxidation and facile preparation of nido-R2C2B4H6 clusters in organic solutions
-
Solutions of pentaborane(9) in tetrahydrofuran (THF) were found to be indefinitely stable under inert conditions and relatively stable to dry air. Solutions exposed to the air were found to decompose slowly to boric acid. Similar stabilities were also found for other pentaborane(9) organic solvent systems including diglyme, diethyl ether, and hexane. No vigorous reactions with air or moisture, including pyrophoric or shock-sensitive behavior, were observed for any of the solutions investigated. The reaction of pentaborane(9) with triethylamine and either 3-hexyne or phenylacetylene in THF at room temperature was found to produce up to 80% of nido-2,3-(CH3CH2)2C2B 4H6 and 20% of nido-2,3-(C6H5)-HC2B4H6, respectively. In addition, the reaction of diphenylacetylene with the pentaborane(9)-THF solution and triethylamine was also explored to determine if the preparation of the synthetically very difficult nido-2,3-(C6H5)2C2B 4H6 carborane could be achieved. The reaction was found to give a 21% yield of the nido-2,3-(C6H5)2C2B 4H6 carborane after 1 day at room temperature. The nature of the interaction between pentaborane(9) and THF has been investigated by ambient- and low-temperature 11B NMR studies.
- Cendrowski-Guillaume, Sophie M.,Spencer, James T.
-
p. 969 - 972
(2008/10/08)
-
- Competition between Triborane as a Ligand and a Hybride Donor at Platinum Centres containing Chelating Phosphines: Molecular Structures of PtB3H7>, PtB3H7> and 2>Cl
-
The reaction of 5-C5H4PPh2)2> with the octahydrotriborate(1-) anion, -, leads to both in which the borane unit acts as a pseudo-bidentate ligand and Cl which results from the borane anion functioning as a hydride donor.For each of the complexes containing a bis(diphenylphosphino)alkane ligand the major product is PtB3H7>, whereas for the reaction of - with 5-C5H4PPh2)2>, 2>Cl is the predominant species formed.Three productshave been structurally characterised: PtB3H7> 1, space group P21/c, a = 16.049(4), b = 15.395(4), c = 21.075(5) Angstroem, β = 90.53(2) deg, Z = 8, R = 0.039; PtB3H7> 3, space group P21, a = 8.8826(18), b = 17.7329(32), c = 9.5520(17) Angstroem, β = 114.115(15) deg, Z = 2, R = 0.032; 2>Cl*3CH2Cl2 6, space group P21/c, a = 12.862(2), b = 38.732(6), c = 14.271(2) Angstroem, β = 99.027(15) deg, Z = 4, R = 0.067.The structure of the cation of 6 resembles that of 2>+ rather than that of t2P(CH2)3PBut2>2>+ thereby indicating that it is the steric bulk of the phosphorus substituents rather than the P-Pt-P bite angle that controls the geometry of the framework and thus the hydride locations.Fenske-Hall molecular orbital calculations have been used to probe the mode of bonding of the hydride ligands to the diplatinum centre.
- Haggerty, Brian S.,Housecroft, Catherine E.,Rheingold, Arnold L.,Shaykh, Bilal A. M.
-
p. 2175 - 2184
(2007/10/02)
-
- 13C nuclear magnetic resonance studies of aromatic amine-borane adducts
-
13C NMR measurements are reported for 22 aromatic amine-borane, 7 aliphatic amine-borane, and 3 aliphatic amine-trimethylborane adducts.Additivity of the substituent effects on the δ 13C values of the aromatic carbon atoms is observed.The δ 13C values are compared with those of the arylamines of arylammonium salts and of corresponding alkyl-substituted benzenes.The δ 13C values for the borane adducts, ammonium salts and hydrocarbons exhibit the same trends.However, in the borane adducts similar to the ammonium salts, part of the shielding of the ortho-carbon atoms is attributed to electric field effects which are much less pronounced in the hydrocarbon analogues.The comparison of δ 13C values of aliphatic amine-borane adducts with those of corresponding hydrocarbons indicates the importance of steric effects.
- Paz-Sandoval, M. A.,Camacho, C.,Contreras, R.,Wrackmeyer, B.
-
p. 1331 - 1336
(2007/10/02)
-
- Main Group Chemistry on a Metal Framework: Reactions of - (R=H, CH3) with Lewis Bases
-
The reactions of - (R=H, CH3) with Lewis bases (L=CO, PhMe2P, NEt3, and H2O) are explored.For R=H and L=PhMe2P, substitution via H2 rather than CO elimination to yield -, Fe(CO)3(PhMe2P)2, and a ferroborane anion spectroscopically characterized in situ.The fragmentation pathway predominates in the presence of excess Lewis base, whereas H2 elimination is favored by low ligand levels.For L=PhMe2P the H2 displacement pathway is promoted with R=CH3.A kinetic study for L=PhMe2P reveals a first-order rate dependence on both substrate and ligand for fragmentation, suggesting associative activation.The dual-fragmentation path observed illustrates competitive base displacement of isoglobal fragments from a single cluster.An analysis at intermediate ligand levels results in the definition of base-promoted cluster substitution via H2 elimination.Under the conditions explored here, CO yields only H2 displacement, H2O only fragmentation, and NEt3 adduct formation with slow fragmentation but no H2 displacement.
- Housecroft, Catherine E.,Fehlner, Thomas P.
-
p. 4867 - 4873
(2007/10/02)
-
- Catalytic Reactions of Metalloporphyrins. 1. Catalytic Modifikation of Borane Reduction of Ketone with Rhodium(III) Porphyrin as Catalyst
-
(Octaethyl- or tetraphenylporphyrinato)rhodium(III) chloride shows an efficient catalysis in the aerobic reduction of ketone with NaBH4 in THF, BH4- + 2R1R2C=O + O2 ->2R1R2CHOH + BO2-.The initial step in the catalytic cycle is the rate-determining complexation of BH4- with RhIII porphyrin (RhIII + BH4- -> RhIII-BH4) followed by a rapid borane transfer from the adduct to ketone to give dialkoxyborane and hydridorhodium species (RhIII-BH4 + 2R1R2C=O -> Rh-H + HB(O-CHR1R2)2).In the subsequent step, the Rh-H species undergoes oxidation with O2 back to RhIII with concomitant "hydrolisis" of dialkoxyborane to alcohol (Rh-H + O2 + HB(O-CHR1R2)2 -> RhIII + 2R1R2CHOH + BO2-).Essentially, autorecycling RhIII and Rh-H act as a "borane" generator and proton source, respectively, in a catalytic manner.Furthermore, the RhIII-BH4 complex capable of transferring borane to ketone lacks what is characteristic of free borane, i.e., facile oxidation with O2 and ready hydrolysis with H2O.Thus, the present system provedes a highly efficient, catalytic modification of synthetic reactions of borane in the presence of oxygen.
- Aoyama, Yasuhiro,Fujisawa, Takeshi,Watanabe, Takamichi,Toi, Hiroo,Ogoshi, Hisanobu
-
p. 943 - 947
(2007/10/02)
-
- NEW AIR-STABLE TRIMETHYLSILYL-SUBSTITUTED TRIVININYLBORANES AND CARBORANES
-
The reaction of B5H9 with (CH3)3SiCCR (R=(CH3)3Si, CH3 or H) without the use of a Lewis base, heat, solvent, or large volume gas bulbs produced air-stable B and 2-(CH3)3Si-3-R-2,3-C2B4H6 in quantitative yields.However, this reaction was very solw.The reaction of BH3*THf with (CH3)3SiCCR at 0 deg C also quantitatively produced the corresponding trivinylborane derivative, in which the boron is bonded exclusively to the silicon bearing olefinic carbon of each of the vinyl groups.The most satisfactory method of preparation of the carborane involved the liquid phase of a mixture of B5H9 and (CH3)3SiCCR at 135 deg C with the formation of hydroborated species in a high vacuum stainless steel reactor.The carborane product was easily isolated in gram quantities in high purity by vacuum fractionation.All new products were characterized by IR, 1H, 11B, 13 C, and 29Si NMR spectroscopy, mass spectrometry, and, where possible, elemental analysis.
- Hosmane, Narayan S.,Sirmokadam, Narayan N.,Mollenhauser, Mark N.
-
p. 359 - 372
(2007/10/02)
-
- Molecular addition compounds. 9. Effect of structure on the reactivities of representative borane-amine complexes in typical reactions such as hydrolysis, hydroboration, and reduction
-
A number of borane-amine complexes with widely different structural features in the amine portion was prepared and their reactivities toward typical B-H reactions, such as hydrolysis, hydroboration of 1-octene, and reduction of cyclohexanone, were studied. BH3-amine complexes containing an N-phenyl group are hydrolyzed by neutral hydroxylic solvents, while others require a strong acid medium for the hydrolysis. In hydroboration, BH3-N-phenylamine complexes react rapidly with 1-octene in THF at 25°C, while all other types require refluxing THF or toluene for reaction. Again, BH3-N-phenylamine complexes reduce cyclohexanone in THF at 25°C at reasonable rates, while others require acetic acid solvent or mineral or Lewis acids to achieve the desired reduction. Thus, among such borane-amine addition compounds, the BH3-N-phenylamines emerge as unique hydroborating and reducing agents. The results of the present study provide insights into the mechanisms of the hydroboration and reduction reactions. The rates of hydroboration of alkenes with BH3-amine complexes are inversely related to the stability of the adduct, arguing for a prior dissociation of the adduct, followed by the reaction of BH3 with the alkene. The reduction of cyclohexanone with BH3-amine complex in THF proceeds by an analogous dissociation mechanism. In acetic acid or in the presence of mineral or Lewis acids, a bimolecular attack of the BH3-amine complex on the protonated carbonyl group has been considered to be the most viable mechanistic pathway. However, this does not account for the effect of acids on hydrolytic behavior. Consequently, caution is urged in considering possible interpretation of the acid-enhanced reactions of amine-boranes.
- Brown, Herbert C.,Murray, Leo T.
-
p. 2746 - 2753
(2008/10/08)
-
- The Reaction between Sulfur or Carbon Disulfide Respectively, and Sodium Borohydride in Amines. Two New Methods for the Preparation of Alkylamine Boranes, R3-nHnN-BH3
-
Sodium borohydride reacts with sulfur in ammonia, primary, secondary or tertiary amines with hydrogen evolution to give the corresponding amine boranes, R3-nHnN-BH3.The reaction of sodium borohydride with carbon disulfide in the presence of a tertiary amine yields compounds R3N-BH3.The formulation of these reactions has been established by 11B and 1H NMR. - Keywords: Amine Boranes
- Binder, Herbert,Diamantikos, Wassilios
-
p. 203 - 207
(2007/10/02)
-
- Simplified synthesis of B10H14 from NaBH4 via B11H14- ion
-
The synthesis of B11H14- ion from BH4- ion and acids, including BF3·O(C2H5)2, BCl3, SiCl4, or alkyl halides, and the subsequent oxidation of the B11H14- ion to produce B10H14 using Na2Cr2O7, KMnO4, H2O2, or H2O2/FeSO4 is described. An optimum procedure is suggested which can be scaled-up.
- Dunks, Gary B.,Barker, Kathryn,Hedaya, Eddie,Hefner, Catherine,Palmer-Ordonez, Kathy,Remec, Peter
-
p. 1692 - 1697
(2008/10/08)
-
- Water‐promoted, open‐flask synthesis of amine‐boranes: 2‐methylpyridine‐borane (2‐picoline‐borane)
-
A procedure yielding 2‐methylpyridine‐borane as a white solid is presented. Sodium borohydride and powdered sodium bicarbonate are added into a single‐necked, air‐dried round‐bottomed flask with a Teflon‐coated, egg‐shaped magnetic stir bar. A discussion on amine‐boranes, reductive amination with aldehyde bisulfites and carbohydrates, and metathesis of metal borohydrides with alkylammonium salts concludes the chapter.
- Kulkarni, Ameya S.,Ramachandran, P. Veeraraghavan
-
-
