- Trends in the proton nuclear magnetic resonance spectra of some amine-haloboranes. Steric effects
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Borane adducts of trimethylamine and diethylamine were halogenated using free halogens or hydrogen halides, and the proton NMR spectra of these amine-haloborane adducts were obtained. The resonances of these adducts showed a shift to lower field with increased size of halogen or with increased number of halogens on boron. This shift to lower field had been previously attributed to inductive effects, but in this work it was shown that the shift to lower field was due to steric interaction between halogens on boron and alkyl groups on nitrogen. Proton NMR spectra for diethylamine-haloboranes were complex and showed patterns attributable to nonequivalent methylene protons. Computer analyses of the spectra allowed assignments consistent with preferred rotational configurations.
- Myers,Ryschkewitsch,Mathur,King
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- AMINE-BORANES AS BIFUNCTIONAL REAGENTS FOR DIRECT AMIDATION OF CARBOXYLIC ACIDS
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The present invention generally relates to a process for selective and direct activation and subsequent amidation of aliphatic and aromatic carboxylic acids to afford an amide R3CONR1R2. That the process is capable of delivering gaseous or low-boiling point amines provides a major advantage over existing methodologies, which involves an intermediate of triacyloxyborane-amine complex [(R3CO2)3—B—NHR1R2]. This procedure readily produces primary, secondary, and tertiary amides, and is compatible with the chirality of the acid and amine involved. The preparation of known pharmaceutical molecules and intermediates has also been demonstrated.
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Paragraph 0007; 0063
(2022/03/04)
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- Activation of sodium borohydride via carbonyl reduction for the synthesis of amine- And phosphine-boranes
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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.
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supporting information
p. 16770 - 16774
(2021/12/08)
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- Visible light-mediated synthesis of amides from carboxylic acids and amine-boranes
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Here, a photocatalytic deoxygenative amidation protocol using readily available amine-boranes and carboxylic acids is described. This approach features mild conditions, moderate-to-good yields, easy scale-up, and up to 62 examples of functionalized amides with diverse substituents. The synthetic robustness of this method was also demonstrated by its application in the late-stage functionalization of several pharmaceutical molecules.
- Chen, Xuenian,Kang, Jia-Xin,Ma, Yan-Na,Miao, Yu-Qi
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supporting information
p. 3595 - 3599
(2021/06/06)
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- Amine-boranes as Dual-Purpose Reagents for Direct Amidation of Carboxylic Acids
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Amine-boranes serve as dual-purpose reagents for direct amidation, activating aliphatic and aromatic carboxylic acids and, subsequently, delivering amines to provide the corresponding amides in up to 99% yields. Delivery of gaseous or low-boiling amines as their borane complexes provides a major advantage over existing methodologies. Utilizing amine-boranes containing borane incompatible functionalities allows for the preparation of functionalized amides. An intermolecular mechanism proceeding through a triacyloxyborane-amine complex is proposed.
- Choudhary, Shivani,Hamann, Henry J.,Ramachandran, P. Veeraraghavan
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supporting information
(2020/11/13)
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- Palladium-catalyzed B-diarylation of diethylaminoborane for the synthesis of diarylborinic acids
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The palladium-catalyzed synthesis of diarylborinic acid derivatives by intermolecular cross-coupling between aryl iodides and (amino)dihydrideborane is reported. The key to success of the reaction is the use of a less bulky diethylaminoborane reagent, which facilitates the second B-arylation.
- Igarashi, Takuya,Shimazumi, Ryoma,Tobisu, Mamoru
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supporting information
p. 760 - 763
(2020/07/10)
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- Amine-boranes bearing borane-incompatible functionalities: Application to selective amine protection and surface functionalization
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The first general open-flask synthesis of amine-boranes with inexpensive and readily available reagents, such as sodium borohydride, sodium bicarbonate, water, and the desired amines is described. Even amines bearing borane-reactive functionalities, such as alkene, alkyne, hydroxyl, thiol, ester, amide, nitrile, and nitro are well tolerated. Some of these novel amine-boranes represent stable molecules containing potentially incompatible electrophilic and nucleophilic centers in proximity. This convenient scalable synthesis provides a novel class of organic ligands for surface functionalization, as demonstrated by the formation of self-assembled layers of thiol- and alkoxysilane-bearing amine-boranes on gold and silica surfaces, respectively.
- Veeraraghavan Ramachandran,Kulkarni, Ameya S.,Zhao, Yan,Mei, Jianguo
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supporting information
p. 11885 - 11888
(2016/10/09)
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- Nucleophilic displacement of ammonia from ammonia borane for the preparation of alkylamine-, pyridine- and phosphine-boranes
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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.
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p. 26207 - 26210
(2014/07/08)
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- Amine-Boranes: Green hypergolic fuels with consistently low ignition delays
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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.
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supporting information
p. 16869 - 16872
(2015/01/09)
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- Heterogeneous dehydrocoupling of amine-borane adducts by skeletal nickel catalysts
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Skeletal Ni, produced by the selective leaching of Al from a Ni/Al alloy, has been successfully employed in the catalytic dehydrogenation of various amineborane adducts. The combination of low cost and facile single-step synthesis make this system a potentially attractive alternative to the previously described precious metal and other first-row metal catalysts. The heterogeneous nature of the catalyst facilitates convenient product purification, and this is the first such system to be based on a first-row transition metal. Catalytic dehydrocoupling of Me2NH·BH3 (1) and Et2NH3 BH3 (5) was demonstrated using 5 mol % skeletal Ni catalyst at 20 °C and produced [Me2N·BH2]2 (2) and [Et2N-BH2]2/Et2NdBH2 (6), respectively. The related adduct iPr2NH3 BH 3 (7) was also dehydrogenated to afford iPr2NdBH2 (8) but with significant catalyst deactivation. Catalytic dehydrocoupling of MeNH2 3 BH3 (9) was found to yield the cyclic triborazane [MeNH-BH 2]3 (10) as the major product, whereas high molecular weight poly- (methylaminoborane) [MeNH-BH2]n (11) (Mw = 78 000 Da, PDI = 1.52) was formed when stoichiometric quantities of Ni were used. Similar reactivity was also observed with NH3 3 BH3 (12), which produced cyclic oligomers and insoluble polymers, [NH2-BH2] xx (14), under catalytic and stoichiometric Ni loadings, respectively. Catalyst recycling was hindered by gradual poisoning. A study of possible catalyst poisons suggested that BH3 was the most likely surface poison, in line with previous work on colloidal Rh catalysts. Catalytic borane adducts using skeletal Cu and Fe was also explored. Skeletal Cu was found to be a less active dehydrogenation catalyst for amine-borane adducts but also yielded poly(methylaminoborane) under stoichiometric conditions on reaction with MeNH2 · BH3 (9). Skeletal Fe was found to be completely inactive towardamine-borane dehydrogenationr
- Robertson, Alasdair P. M.,Suter, Riccardo,Chabanne, Laurent,Whittell, George R.,Manners, Ian
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p. 12680 - 12691
(2012/02/15)
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- Dehydrocoupling reactions of borane-secondary and -primary amine adducts catalyzed by group-6 carbonyl complexes: Formation of aminoboranes and borazines
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Photoirradiation of a solution of BH3·NHR2 (1a: R = Me, 1b: R = 1/2C4H8, 1c: R = 1/2C 5H10, 1f: R = Et) containing a catalytic amount of a group-6 metal carbonyl complex, [M(CO)6] (M = Cr, Mo, W), led to dehydrogenative B-N covalent bond formation to produce aminoborane dimers, [BH2NR2]2 (2a-c, f), in high yield. During these reactions a borane σ complex, [M(CO)5(η1- BH3·NHR2)] (3), was detected by NMR spectroscopy. Similar catalytic dehydrogenation of bulkier amineboranes, BH 3·NHiPr2 (1d) and BH3· NHCy2 (1e, Cy = cyclo-C6H11), afforded monomeric products BH2=NR2 (4d, e). The reaction mechanism of the dehydrocoupling was investigated by DFT calculations. On the basis of the computational study, we propose that the catalytic dehydrogenation reactions proceed via an intramolecular pathway and that the active catalyst is [Cr(CO)4]. The reaction follows a stepwise mechanism involving NH and BH activation. Dehydrocoupling of borane-primary amine adducts BH 3·NH2R (1g: R = Me, 1h: R = Et, 1i: R = tBu) gave borazine derivatives [BHNR]3 (5g-i).
- Kawano, Yasuro,Uruichi, Mikio,Shimoi, Mamoru,Taki, Seitaro,Kawaguchi, Takayuki,Kakizawa, Taeko,Ogino, Hiroshi
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p. 14946 - 14957
(2010/01/16)
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- Synthesis of N-substituted derivatives of the hypho-(amine)(amino)B8H11 system
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The chemistry of the hypho-(amine)(amino)B8H11 system is developed by the synthesis of several derivatives by three routes. [(Et2HN)B8H11NEt2] (4), characterised by single-crystal X-ray work, is prepared from the reaction between B9H13(SMe2) and Et2NH. Methylation of [(EtH2N)B8H11NHEt] (1) using NaH and MeI gives, successively, [(EtMeHN)B8H11NHEt] (5), [(EtMe2N)B8H11NHEt] (6) and [(EtMe2N)B8H11NMeEt] (7). Alternatively, a displacement reaction with NHEt2 on (1) or on [(MeH2N)B8H11NHMe] (2) yields [(Et2HN)B8H11NHEt] (8) or [(Et2HN)B8H11NHMe] (9), and a displacement on (1) with pyridine yields [(C5H5N)B8H11NHEt] (10). Phosphine-containing derivatives [(Ph3P)B8H11NHEt] (11) and [(PhMe2P)B8H11NHEt] (12) can be isolated from interaction of (1) with PPh3, [RhCl(PPh3)3] or [PtCl2(PMe2Ph)2].
- D?rfler, Udo,Bauer, Claudia,Gabel, Detlef,Rath, Nigam P.,Barton, Lawrence,Kennedy, John D.
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p. 215 - 222
(2007/10/03)
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- Synthesis and Coordination of a Cleft-Stabilized Triphosphazane Hydride: C6H4N2[P(S)(NEt2)2] 2PH
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Reaction of the molecular cleft-containing triphosphazane C6H4N2[P(S)(NEt2)2] 2PCl (2) with LiBH4 yields the borane-coordinated triphosphazane hydride C6H4N2[P(S)(NEt2)2] 2P(BH3)H (3). The complex is strongly associated; free hydride C6H4N2[P(S)(NEt2)2] 2PH (4) can be obtained by treatment of 3 with tertiary amines. Complex 3 reacts with (norbornadiene)Mo(CO)4 to form triphosphazane complexes {C6H4N2[P(S)(NEt2)2] 2PH}Mo(CO)3 (5), {C6H4N2[P(S)(NEt2)2] 2P(BH2)}Mo(CO)4 (6), and {C6H4N2[P(S)(NEt2)2] 2P(BH2)}Mo(CO)5 (7). Under more vigorous conditions 2 and Mo(CO)6 yield 5 and {C6H4N5[P(S)(NEt2)2] 2PH}Mo(CO)4 (8). Compounds 3-8 were characterized by spectral data. X-ray analyses were performed on 6 and 7: 6, monoclinic, P21/c, a = 10.6350-(10) A, b = 18.979(3) A, c = 18.204(3) A, β= 91.750(10)°, V = 3672.6(9) A3, Z = 4, R = 0.044, Rw = 0.038; 7, triclinic, P1, a = 11.080(2) A, b = 11.253(3) A, c = 17.739(4) A, α = 94.86(2)°, β= 104.57(2)°, γ = 101.85(2)°, V = 2073.2(8) A3, Z = 2, R = 0.040, Rw = 0.047. Structures are compared, and the influence of the molecular cleft on reaction outcome and the involvement of the peripheral sulfur atoms in coordination are discussed.
- Young, Susan M.,Carperos, Vasili,Norman, Arlan D.
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p. 2000 - 2005
(2008/10/09)
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- 13C nuclear magnetic resonance studies of aromatic amine-borane adducts
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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.
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p. 1331 - 1336
(2007/10/02)
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- 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
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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
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p. 203 - 207
(2007/10/02)
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- Dialkylaminohydridophenoxyboranes. Convenient preparation and studies of intramolecular boron-nitrogen π bonding
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A convenient preparation of dialkylaminohydridophenoxyborane compounds (HBOC6H5NR'2) has been developed according to the following three-step sequence: (1) 4BF3 (etherate) + 3NaBH4 = 3NaBF4 + 2B2H6(g); (2) 1/2B2H6(g) + HNR'2 = H3BNHR'2; (3) H3BHNR'2 + HOC6H5 + heat = 2H2 + HBOC6H5NR'2; HNR'2 = HN(CH3)2, HN(C2H5)2, HN(i-C3H7)2, HN(n-C4H9)2, HN(CH2C6H5)2, HNC4H8, and HNC5H10. The final products are isolated in yields ranging from 70 to 90% by vacuum distillation at moderate temperatures. Molecular association and variable-temperature proton magnetic resonance studies of these compounds in benzene solution are consistent with a planar, monomeric configuration with considerable π interaction between boron and nitrogen and hindered rotation about this bond. The Lewis acid behavior of diisopropylaminohydridophenoxyborane toward ammonia and trimethylamine was determined using a tensimetric titration procedure. No evidence of interaction was observed with trimethylamine while a stable 1:1 adduct was formed in the case of the reaction involving ammonia: HBOC6H5N(i-C3H7)2 + NH3 = HBOC6H5N(i-C3H7)2-NH 3. The room-temperature proton magnetic resonance spectrum of the ammonia adduct of diisopropylaminohydridophenoxyborane has demonstrated relatively unrestricted rotation about the secondary amino nitrogen-boron bond.
- Kovar, Roger A.,Waldvogle, Gene G.
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p. 2239 - 2243
(2008/10/08)
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- A convenient synthesis of aminoboranes
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Detailed studies of the synthesis of aminoboranes by the reduction of phenyl borate with aluminum and hydrogen in the presence of secondary amines have been carried out. The amines used were diethylamine, diisopropylamine, and piperidine and the nature of the product formed was found to be a function of the phenyl borate : amine ratio. For example, tris(diethylamino)borane (81%) is prepared in admixture with bis(diethylamino)borane (5%) when diethylamine is used as the solvent whereas bis(diethylamino)borane is prepared exclusively and in high yield (80%) when phenyl borate and diethylamine are employed in a 1:2 molar ratio in benzene solvent. Aluminum-hydrogen reduction of equimolar quantities of phenyl borate and diethylamine in benzene solvent did not afford a high yield of the expected diethylaminoborane. Instead, nearly equimolar quantities of diethylaminohydridophenoxyborane [HB(OC6H5)N(C2H5)2] and diethylaminobis(phenoxy)borane [B(OC6H5)2N(C2H5) 2] were isolated. This reaction was found to be insensitive to changes in reaction time or temperature. The reaction sequence proposed to explain formation of the latter products involves (1) intermediate formation of AlH3 [Al + 3/2H2 → AlH3], (2) reaction between AlH3 and diethylamine forming the more thermodynamically stable bis(diethylamino)alane AlH3 + R2NH → AlH3NR2H → -H2 H2AlNR2 → -H2 R2NH HA1(NR2)2 and (3) reduction of phenyl borate by bis(diethylamino)alane [2B(OC6H5)3 + HAl(NR2)2 → HB(OC6H5)NR2 + B(OC6H5)2NR2 + Al(OC6H5)3]. Exchange studies between a number of aminoalanes and borate esters were also carried out.
- Kovar, Roger A.,Culbertson,Ashby
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p. 900 - 905
(2008/10/08)
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- Water‐promoted, open‐flask synthesis of amine‐boranes: 2‐methylpyridine‐borane (2‐picoline‐borane)
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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
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