- BASIC STUDY OF THE AMINO ACID RESIDUE IN PROTEIN. THE ROLE OF HYDROCARBON GROUPS IN ENANTIOMER-DIFFERENTIATING ACYLATION.
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The enantiomer-differentiation acylation (kinetic resolution) of 1-phenylalkylamines and their derivatives was carried out with (S)-2-phenylbutyric anhydride and its derivatives in aqueous and nonaqueous media. On the basis of the distributions of the two diastereomeric products, the molecular interactions between hydrocarbon residues responsible for the structural recognition of the reacting molecules were studied. In nonpolar media, the (R,S)-isomer was predominantly formed over the (S,S)-isomer. Moreover, the differentiation was mainly controlled by the size of the alkyl substituents of the substrates.
- Hiraki,Tai
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Read Online
- A highly fluorescent metallosalalen-based chiral cage for enantioselective recognition and sensing
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A highly fluorescent coordination cage [Zn8L4I 8] has been constructed by treating enantiopure pyridyl- functionalized metallosalalen units (L) with zinc(II) iodide and characterized by a variety of techniques including microanalysis, thermogravimetric analysis (TGA), circular dichroism (CD) spectroscopy, and single-crystal and powder X-ray diffraction. Strong intermolecular π-π, CH-π, and CH-I interactions direct packing of the cage molecules to generate a 3D polycage network interconnected by pentahedral cages formed by adjacent pentamers. The cage has an amphiphilic helical cavity decorated with chiral NH functionalities capable of interactions with guest species such as saccharides. The fluorescence of the cage was greatly enhanced by five enantiomeric saccharides in solution, with enantioselectivity factors of 2.480-4.943, and by five enantiomeric amines in the solid state, with enantioselective fluorescence enhancement ratios of 1.30-3.60. This remarkable chiral sensing of both saccharides and amines with impressive enantioselectivity may result from the steric confinement of the cavity as well as its conformational rigidity. It holds great promise for the development of novel chiral cage materials for sensing applications. Cage-based chiral sensor: A highly fluorescent coordination cage [Zn8L 4I8] can be prepared from enantiopure pyridyl- functionalized metallosalalen units (L). The cage has an amphiphilic helical cavity decorated with chiral NH functionalities and supramolecular interactions generate a 3D polycage network interconnected by pentahedral cages formed by adjacent pentamers (see graphic). The fluorescence of the cage is greatly enhanced either in solution or in the solid state in the presence of enantiomeric saccharides or amines, respectively, with significant enantioselectivity factors.
- Dong, Jinqiao,Zhou, Yanfang,Zhang, Fangwei,Cui, Yong
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Read Online
- Chemoselective and Tandem Reduction of Arenes Using a Metal–Organic Framework-Supported Single-Site Cobalt Catalyst
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The development of heterogeneous, chemoselective, and tandem catalytic systems using abundant metals is vital for the sustainable synthesis of fine and commodity chemicals. We report a robust and recyclable single-site cobalt-hydride catalyst based on a porous aluminum metal–organic framework (DUT-5 MOF) for chemoselective hydrogenation of arenes. The DUT-5 node-supported cobalt(II) hydride (DUT-5-CoH) is a versatile solid catalyst for chemoselective hydrogenation of a range of nonpolar and polar arenes, including heteroarenes such as pyridines, quinolines, isoquinolines, indoles, and furans to afford cycloalkanes and saturated heterocycles in excellent yields. DUT-5-CoH exhibited excellent functional group tolerance and could be reusable at least five times without decreased activity. The same MOF-Co catalyst was also efficient for tandem hydrogenation–hydrodeoxygenation of aryl carbonyl compounds, including biomass-derived platform molecules such as furfural and hydroxymethylfurfural to cycloalkanes. In the case of hydrogenation of cumene, our spectroscopic, kinetic, and density functional theory (DFT) studies suggest the insertion of a trisubstituted alkene intermediate into the Co–H bond occurring in the turnover limiting step. Our work highlights the potential of MOF-supported single-site base–metal catalysts for sustainable and environment-friendly industrial production of chemicals and biofuels.
- Antil, Neha,Kumar, Ajay,Akhtar, Naved,Begum, Wahida,Chauhan, Manav,Newar, Rajashree,Rawat, Manhar Singh,Manna, Kuntal
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supporting information
p. 1031 - 1040
(2022/01/19)
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- Direct Synthesis of α-Amino Nitriles from Sulfonamides via Base-Mediated C-H Cyanation
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Herein, we disclose a transition-metal-free reaction system that enables α-cyanation of sulfonamides through C-H bond cleavage for the preparation of α-amino nitriles, including difficult-to-access all-alkyl α-tertiary scaffolds. More than 50 substrate examples prove a wide functional group tolerance. Additionally, its synthetic practicality is highlighted by gram-scalability and the late-stage modification of natural compounds. Mechanistic experiments suggest that this process involves in situ formation of an imine intermediate via base-promoted elimination of HF.
- Shi, Shasha,Yang, Xianyu,Tang, Man,Hu, Jiefeng,Loh, Teck-Peng
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supporting information
p. 4018 - 4022
(2021/05/26)
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- Asymmetric synthesis of primary amines catalyzed by thermotolerant fungal reductive aminases
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Chiral primary amines are important intermediates in the synthesis of pharmaceutical compounds. Fungal reductive aminases (RedAms) are NADPH-dependent dehydrogenases that catalyse reductive amination of a range of ketones with short-chain primary amines supplied in an equimolar ratio to give corresponding secondary amines. Herein we describe structural and biochemical characterisation as well as synthetic applications of two RedAms fromNeosartoryaspp. (NfRedAm andNfisRedAm) that display a distinctive activity amongst fungal RedAms, namely a superior ability to use ammonia as the amine partner. Using these enzymes, we demonstrate the synthesis of a broad range of primary amines, with conversions up to >97% and excellent enantiomeric excess. Temperature dependent studies showed that these homologues also possess greater thermal stability compared to other enzymes within this family. Their synthetic applicability is further demonstrated by the production of several primary and secondary amines with turnover numbers (TN) up to 14 000 as well as continous flow reactions, obtaining chiral amines such as (R)-2-aminohexane in space time yields up to 8.1 g L?1h?1. The remarkable features ofNfRedAmand NfisRedAm highlight their potential for wider synthetic application as well as expanding the biocatalytic toolbox available for chiral amine synthesis.
- Cosgrove, Sebastian C.,Grogan, Gideon,Mangas-Sanchez, Juan,Marshall, James R.,Palmer, Ryan B.,Ramsden, Jeremy I.,Sharma, Mahima,Thorpe, Thomas W.,Turner, Nicholas J.
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p. 5052 - 5057
(2020/06/09)
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- Ruthenium Catalyzed Direct Asymmetric Reductive Amination of Simple Aliphatic Ketones Using Ammonium Iodide and Hydrogen
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The direct conversion of ketones into chiral primary amines is a key transformation in chemistry. Here, we present a ruthenium catalyzed asymmetric reductive amination (ARA) of purely aliphatic ketones with good yields and moderate enantioselectivity: up to 99 percent yield and 74 percent ee. The strategy involves [Ru(PPh3)3H(CO)Cl] in combination with the ligand (S,S)-f-binaphane as the catalyst, NH4I as the amine source and H2 as the reductant. This is a straightforward and user-friendly process to access industrially relevant chiral aliphatic primary amines. Although the enantioselectivity with this approach is only moderate, to the extent of our knowledge, the maximum ee of 74 percent achieved with this system is the highest reported till now apart from enzyme catalysis for the direct transformation of ketones into chiral aliphatic primary amines.
- Ernst, Martin,Ghosh, Tamal,Hashmi, A. Stephen K.,Schaub, Thomas
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supporting information
(2020/07/14)
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- Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation
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Titania (TiO2) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO2 surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti8(μ2-O)8(μ2-OH)4 node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO2 support to enable CoII-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported CoII-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of TiIII in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO2-supported heterogeneous catalysts.
- Ji, Pengfei,Song, Yang,Drake, Tasha,Veroneau, Samuel S.,Lin, Zekai,Pan, Xiandao,Lin, Wenbin
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p. 433 - 440
(2018/01/17)
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- Amide Synthesis via Aminolysis of Ester or Acid with an Intracellular Lipase
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A unique lipase (SpL) from Sphingomonas sp. HXN-200 was discovered as the first intracellular enzyme for the aminolysis of ester or acid to produce amide. Reactions of a series of esters and amines with SpL gave the corresponding amides 3a-g in high yield with high activity. SpL also showed high enantioselectivity and high activity for enantioselective ester aminolysis, producing amides (R)-3h-j in high ee from the corresponding racemic ester or amine. Moreover, SpL was found to be highly active for the aminolysis of carboxylic acid, which was generally considered infeasible with the known aminolysis enzymes. The aminolysis of several carboxylic acids afforded the corresponding amides 3a, 3d, 3k, 3l, and 3n in good yield. The intracellular SpL was expressed in Escherichia coli cells to give an efficient whole-cell biocatalyst for amide synthesis. Remarkably, high catalytic activity was observed in the presence of water at 2-4% (v/v) for free enzyme and 16% (v/v) for whole cells, respectively. Accordingly, E. coli (SpL) wet cells were used as easily available and practical catalysts for the aminolysis of ester or acid, producing a group of useful and valuable amides in high concentration (up to 103 mM) and high yield. The newly discovered intracellular SpL with unique properties is a promising catalyst for green and efficient synthesis of amides.
- Zeng, Shichao,Liu, Ji,Anankanbil, Sampson,Chen, Ming,Guo, Zheng,Adams, Joseph P.,Snajdrova, Radka,Li, Zhi
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p. 8856 - 8865
(2018/09/06)
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- O -Phthalaldehyde catalyzed hydrolysis of organophosphinic amides and other P(O)-NH containing compounds
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Over 50 years ago, Jencks and Gilchrist showed that formaldehyde catalyses the hydrolysis of phosphoramidate through electrophilic activation, induced by covalent attachment to its nitrogen atom. Given our interest in the use of aldehydes as catalysts, this work was revisited to identify a superior catalyst, o-phthalaldehyde, which facilitates hydrolyses of various organophosphorus compounds bearing P(O)-NH subunits under mild conditions. Interestingly, chemoselective hydrolysis of the P(O)-N bonds could be accomplished in the presence of P(O)-OR bonds.
- Li, Bin-Jie,Simard, Ryan D.,Beauchemin, André M.
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supporting information
p. 8667 - 8670
(2017/08/10)
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- Imine Reductase-Catalyzed Intermolecular Reductive Amination of Aldehydes and Ketones
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Imine reductases (IREDs) have emerged as promising biocatalysts for the synthesis of chiral amines. In this study, the asymmetric imine reductase-catalyzed intermolecular reductive amination with NADPH as the hydrogen source was investigated. A highly chemo- and stereoselective imine reductase was applied for the reductive amination by using a panel of carbonyls with different amine nucleophiles. Primary and secondary amine products were generated in moderate to high yields with high enantiomeric excess values. The formation of the imine intermediate was studied between carbonyl substrates and methylamine in aqueous solution in the pH range of 4.0 to 9.0 by 1H NMR spectroscopy. We further measured the kinetics of the reductive amination of benzaldehyde with methylamine. This imine reductase-catalyzed approach constitutes a powerful and direct method for the synthesis of valuable amines under mild reaction conditions. IRED all about it: The intermolecular asymmetric reductive amination of carbonyls catalyzed by a stereoselective imine reductase produces chiral amines in high yields with high enantioselectivities. The reaction efficiency is attributed to its remarkable tolerance to high concentrations of amine nucleophiles, high pH values, high chemoselectivity towards imines, and high stereoselectivity of the biocatalyst.
- Scheller, Philipp N.,Lenz, Maike,Hammer, Stephan C.,Hauer, Bernhard,Nestl, Bettina M.
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p. 3239 - 3242
(2015/10/28)
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- CATALYST COMPOUNDS
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The present invention relates to an iridium-based catalyst compound for hydrogenating reducible moieties, especially imines and iminiums, the catalyst compounds being defined by the formulas: where ring B is either itself polycyclic, or ring B together with R is polycyclic. The catalysts of the invention are particularly effective in reductive amination procedures 10 which involve the in situ generation of the imine or iminium under reductive hydrogenative conditions.
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Paragraph 0314; 0322
(2015/03/28)
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- Primary amines by transfer hydrogenative reductive amination of ketones by using cyclometalated IrIII catalysts
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Cyclometalated iridium complexes are found to be versatile catalysts for the direct reductive amination (DRA) of carbonyls to give primary amines under transfer-hydrogenation conditions with ammonium formate as both the nitrogen and hydrogen source. These complexes are easy to synthesise and their ligands can be easily tuned. The activity and chemoselectivity of the catalyst towards primary amines is excellent, with a substrate to catalyst ratio (S/C) of 1000 being feasible. Both aromatic and aliphatic primary amines were obtained in high yields. Moreover, a first example of homogeneously catalysed transfer-hydrogenative DRA has been realised for β-keto ethers, leading to the corresponding β-amino ethers. In addition, non-natural α-amino acids could also be obtained in excellent yields with this method. Reduce the work! A broad range of ketones have been successfully aminated to afford primary amines under transfer-hydrogenation conditions by using ammonium formate as the amine source and 0.1 mol % of a cyclometalated IrIII catalyst (see scheme). Copyright
- Talwar, Dinesh,Salguero, Noemi Poyatos,Robertson, Craig M.,Xiao, Jianliang
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supporting information
p. 245 - 252
(2014/01/17)
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- Microwave-Enhanced Asymmetric Transfer Hydrogenation of N-(tert-Butylsulfinyl)imines
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Microwave irradiation has considerably enhanced the efficiency of the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in isopropyl alcohol catalyzed by a ruthenium complex bearing the achiral ligand 2-amino-2-methylpropan-1-ol. In addition to shortening reaction times for the transfer hydrogenation processes to only 30 min, the amounts of ruthenium catalyst and isopropyl alcohol can be considerably reduced in comparison with our previous procedure assisted by conventional heating, which diminishes the environmental impact of this new protocol. This methodology can be applied to aromatic, heteroaromatic and aliphatic N-(tert-butylsulfinyl)ketimines, leading, after desulfinylation, to the expected primary amines in excellent yields and with enantiomeric excesses of up to 96 %. Microwave irradiation promotes the asymmetric transfer hydrogenation of N-(tert-butylsulfinyl)imines in 2-propanol catalysed by a ruthenium complex bearing an achiral β-amino alcohol as ligand. After desulfinylation, α-branched primary amines containing aromatic, heteroaromatic and aliphatic substituents are obtained in excellent yields and with enantiomeric excesses of up to 96 %.
- Pablo, Oscar,Guijarro, David,Yus, Miguel
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p. 7034 - 7038
(2016/02/19)
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- CATALYST COMPOUNDS
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The present invention relates to an iridium-based catalyst compound for hydrogenating reducible moieties, especially imines and iminiums, the catalyst compounds being defined by the formulas: where ring B is either itself polycyclic, or ring B together with R is polycyclic. The catalysts of the invention are particularly effective in reductive amination procedures 10 which involve the in situ generation of the imine or iminium under reductive hydrogenative conditions.
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Paragraph 00163; 00171
(2013/11/05)
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- N-octanoyldimethylglycine trifluoroethyl ester, an acyl donor leading to highly enantioselective protease-catalysed kinetic resolution of amines
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The use of N-octanoyldimethylglycine trifluoroethyl ester as acyl donor in the kinetic resolution of aliphatic amines catalysed by proteases led to enantiomeric ratios >200 in most cases. The resolutions mediated by Protex 6L were shown to be much faster
- Queyroy, Severine,Vanthuyne, Nicolas,Gastaldi, Stephane,Bertrand, Michele P.,Gil, Gerard
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supporting information; experimental part
p. 1759 - 1764
(2012/08/08)
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- Enzymatic racemization of amines catalyzed by enantiocomplementary ω-Transaminases
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A strategy for the biocatalytic racemization of primary α-chiral amines was developed by employing a pair of stereocomplementary PLP-dependent ω-transaminases. The interconversion of amine enantiomers proceeded through reversible transamination by a prochiral ketone intermediate, either catalyzed by a pair of stereocomplementary ω-transaminases or by a single enzyme possessing low stereoselectivity. To tune the system, the type and concentration of a nonchiral amino acceptor proved to be crucial. Finally, racemization could be achieved by the cross-transamination of two different amines without a requirement for an external amino acceptor. Several synthetically and industrially important amines could be enzymatically racemized under mild reaction conditions. ω-Transaminases play ping-pong: A biocatalytic protocol for the 'clean' racemization of α-chiral prim-amines was developed by an equilibrium-controlled deamination/amination sequence catalyzed by a pair of (R)- and (S)-ω-transaminases (see scheme).
- Koszelewski, Dominik,Grischek, Barbara,Glueck, Silvia M.,Kroutil, Wolfgang,Faber, Kurt
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experimental part
p. 378 - 383
(2011/03/21)
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- Asymmetric synthesis of chiral primary amines by transfer hydrogenation of N -(tert -Butanesulfinyl)ketimines
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(Figure presented) The diastereoselective reduction of (R)-N-(tert- butanesulfinyl)ketimines by a ruthenium-catalyzed asymmetric transfer hydrogenation process in isopropyl alcohol, followed by desulfinylation of the nitrogen atom, is an excellent method to prepare highly enantiomerically enriched α-branched primary amines (up to >99% ee) in short reaction times (1-4 h). (1S,2R)-1-Amino-2-indanol has been shown to be a very efficient ligand to perform this transformation. Ketimines bearing either an aryl or a heteroaryl group and an alkyl group as substituents of the iminic carbon atom are very good substrates for this process. The reduction of a dialkyl ketimine could also be achieved, affording the expected amine with moderate optical purity (69% ee). Some amines which are precursors of very interesting biologically and pharmacologically active compounds have been prepared in excellent yields and enantiomeric excesses.
- Guijarro, David,Pablo, Oscar,Yus, Miguel
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supporting information; experimental part
p. 5265 - 5270
(2010/10/21)
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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 63
(2010/12/31)
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- Deracemisation of α-chiral primary amines by a one-pot, two-step cascade reaction catalysed by ω-transaminases
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Racemic a-chiral primary amines were deracemised to optically pure amines in up to >99 % conversion and >99 % ee within 48 h. The deracemisation was a result of a stereoinver- sion of one amine enantiomer; the formal stereoinversion was achieved by a one-pot, two-step procedure: in the first step, kinetic resolution of the chiral racemic amine was performed by employing a -transaminase to yield an intermediate ketone and the remaining optically pure amine; in the second step, the ketone intermediate was stereoselectively transformed into the amine by employing alanine as the amine donor and a -transaminase displaying opposite stereopref- erence than the -transaminase in the first step. In the second step, lactate dehydrogenase was used to remove the side product pyruvate to shift the unfavourable reaction equilibrium to the product side. Depending on the order of the en- antiocomplementary enzymes employed in the cascade, the (R), as well as the (S), enantiomer was accessible.
- Koszelewski, Dominik,Clay, Dorina,Rozzell, David,Kroutil, Wolfgang
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supporting information; experimental part
p. 2289 - 2292
(2009/08/09)
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- Heterogeneous raney nickel and cobalt catalysts for racemization and dynamic kinetic resolution of amines
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Raney metals were studied as heterogeneous catalysts for racemization and dynamic kinetic resolution (DKR) of chiral amines, as an alternative to metals like palladium or ruthenium. Both Raney nickel and cobalt were able to selectively racemize various chiral amines with high selectivity. In the racemization of benzylic primary amines, the minor formation of side products, e.g., secondary amines, can be suppressed by varying the hydrogen pressure. In the racemization of aliphatic amines over Raney catalysts, the selectivity is very high, with the enantiomeric amine as the sole product. DKR of racemic aliphatic amines can be performed with immobilized Candida antarctica lipase B and Raney nickel in one pot; for 2-hexylamine, a yield of 95% of the acetylated amide was achieved, with 97% ee. Attention is devoted to the compatibility of the enzyme and the metal catalyst during the DKR. For benzylic primary amines, a two-pot process is proposed in which the liquid is alternatingly shuttled between two vessels containing the solid racemization catalyst and the biocatalyst. After 4 such cycles, the amide of (R)-1-phenylethylamine was obtained with 94% yield and more than 90% ee.
- Parvulescu, Andrei N.,Jacobs, Pierre A.,De Vos, Dirk E.
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scheme or table
p. 113 - 121
(2009/04/16)
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- Highly selective enzymatic kinetic resolution of primary amines at 80°C: A comparative study of carboxylic acids and their ethyl esters as acyl donors
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(Chemical Equation Presented) Optimization of the kinetic resolution of 2-amino-4-phenyl-butane was achieved at 80°C using CAL-B-catalyzed aminolysis of carboxylic acids and their ethyl esters. The reactions carried out with long chain esters and the corresponding acids as acyl donors proceeded with remarkably high enantioselectivity. The use of carboxylic acids as acylating agents led to a marked acceleration of the reaction rate compared to their ester counterparts. Laurie acid led to enantiomeric excesses superior to 99.5% for both the remaining amine and the corresponding lauramide at 50% conversion (reached in 3 h). These optimized conditions were applied to the resolution of a series of aliphatic and benzylic amines.
- Nechab, Malek,Azzi, Nadia,Vanthuyne, Nicolas,Bertrand, Michele,Gastaldi, Stephane,Gil, Gerard
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p. 6918 - 6923
(2008/02/11)
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- Highly efficient resolutions with isopropylidene glycerol 3-carboxy-2-naphthoate
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A number of chiral 1-arylethylamines and 1-alkylethylamines were resolved with the 3-carboxy-2-naphthoate of isopropylidene glycerol 2, previously reported to be an even more efficient resolving agent for 1-phenylethylamine than the corresponding hemiphthalate 1. The results obtained for the 1-arylethylamines confirm such a trend, revealing impressive resolution ability, in particular, for 1-(4-bromophenyl)-, 1-(4-nitrophenyl)- and 1-(2-naphthyl)ethylamine, whose enantiomers were almost quantitatively separated with (S)-2 by a single precipitation of the less soluble (S,S) diastereomeric salt. Additionally, the success of the resolutions of 1-alkylethylamines (1-phenyl-2-propylamine, 1-cyclohexylethylamine and 2-butylamine), which could not be resolved with 1, indicates that the novel carboxy ester 2 has a wider range of application than 1.
- Pallavicini, Marco,Bolchi, Cristiano,Fumagalli, Laura,Valoti, Ermanno,Villa, Luigi
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p. 2277 - 2282
(2007/10/03)
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- Catalytic Leuckart-Wallach-type reductive amination of ketones
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A Cp*Rh(III) complex catalyzes reductive amination of ketones using HCOONH4 at 50-70°C to give the corresponding primary amines in high yields. The reaction is clean and operationally simple and proceeds at a lower temperature and with higher chemoselectivity than the original Leuckart-Wallach reaction. The new method has been applied to the synthesis of α-amino acids directly from α-keto acids.
- Kitamura, Masato,Lee, Donghyun,Hayashi, Shinnosuke,Tanaka, Shinji,Yoshimura, Masahiro
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p. 8685 - 8687
(2007/10/03)
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- Stereoselective transformation of amines via chiral 2,4,6-triphenylpyridinium intermediates
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We herein report the preparation and the nucleophilic substitution of the chiral 2,4,6-triphenylpyridinium tetrafluoroborates 2a and 2b. The triphenylpyridinium intermediates were generated from homochiral amines (1a, 1b) and 2,4,6-triphenylpyrylium tetrafluoroborate and used as substrates for stereoselective nucleophilic substitution. The degree of inversion in the substitution reactions has been studied. The alcohol (3a, 3b) and azide (4a, 4b) products were obtained with >99 and 96-98% inversion of configuration, respectively.
- Said, Sadri A.,Fiksdahl, Anne
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p. 1947 - 1951
(2007/10/03)
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- Catalytic hydrogenation of aromatic amines at atmospheric pressure in water
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Rhodium on alumina (5% Rh) has been found to be a good catalyst for the hydrogenation of aromatic amines under atmospheric pressure at room temperature in water.
- Strotmann,Butenschon
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p. 4173 - 4176
(2007/10/03)
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- Diastereoselective addition of methyllithium and dimethylcuprate-boron trifluoride to imines derived from (S)-1-phenylethylamine
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The reactions of dimethylcuprate-boron trifluoride reagents with the imines derived from (S)-1-phenylethylamine afforded the secondary amines by addition to the Si face of the imines. (S,S)-bis(1-phenylethyl)amine and (S)-1-cyclohexylethanamine were prepa
- Alvaro, Giuseppe,Savoia, Diego,Valentinetti, Maria R.
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p. 12571 - 12586
(2007/10/03)
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- Catalytic asymmetric reductive amination of ketones via highly enantioselective hydrogenation of the C=N double bond
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We describe a convenient, chemoselective asymmetric reductive amination procedure for the conversion of ketones to chiral hydrazines and amines. The key step in the three-step process is enantioselective DuPHOS-Rh-catalyzed hydrogenation of the C=N double bond of N-acylhydrazones. Detailed optimization studies revealed the effect of solvent, temperature, and the N- acyl group on the enantioselectivity and catalytic efficiency of the reaction. The reduction products, N-acylhydrazines, were converted to hydrazines or amines through hydrolysis or treatment with samarium(II) iodide, respectively.
- Burk, Mark J.,Martinez, Jose P.,Feaster, John E.,Cosford, Nick
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p. 4399 - 4428
(2007/10/02)
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- Chiral Synthesis via Organoboranes. 30. Facile Synthesis, by the Matteson Asymmetric Homologation Procedure, of α-Methyl Boronic Acids Not Available from Asymmetric Hydroboration and Their Conversion into the Corresponding Aldehydes, Ketones, Carboxylic Acids, and Amines of High Enan...
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2-(α-Methylalkyl)- or 2-(α-arylethyl)-1,3,2-dioxaborinanes, RMeHC*BO2(CH2)3 (R = alkyl or aryl), of very high enantiomeric purity, not available from asymmetric hydroboration, can be prepared by the Matteson asymmetric homologation procedure of optically pure pinanediol or 2,3-butanediol boronate esters with (dichloromethyl)lithium, LiCHCl2, conveniently generated in situ in THF at -78 deg C, followed by reaction with either a Grignard reagent or an alkyllithium, with subsequent removal of the chiral auxiliaries. α-Methyl boronic esters thus obtained are readily converted into the corresponding aldehydes by the reaction with lithium (MPML) and mercuric chloride, followed by oxidation with hydrogen peroxide in a pH 8 buffer medium.The two-phase aqueous chromic acid procedure can be used to oxidize these aldehydes to the corresponding α-methyl carboxylic acids of very high enantiomeric purity without significant racemization.Additionally, pinanediol or 2,3-butanediol α-methylorganylboronate esters can be conveniently converted into borinic ester derivatives, RMeHC*BMe(OMe), of very high enantiomeric purity by reaction with methyllithium, followed by treatment with methanolic hydrogen chloride and subsequent recovery of the valuable chiral auxiliaries.These borinic ester derivatives are converted into α-methyl ketones and α-methyl primary amines of known absolute configuration by the α,α-dichloromethyl methyl ether (DCME) reaction and the reaction with hydroxylamine-O-sulfonic acid, respectively.The present synthesis of chiral 2-organyl-1,3,2-dioxaborinanes by the Matteson route, together with our direct asymmetric hydroboration procedure, makes it possible to synthesize many chiral boronic acid derivatives in very high enantiomeric purities.These complementary procedures greatly expand the scope of asymmetric synthesis via chiral organoboranes.
- Rangaishenvi, Milind V.,Singaram, Bakthan,Brown, Herbert C.
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p. 3286 - 3294
(2007/10/02)
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- Asymmetric Syntheses. Part 11. Reduction of Ketones and Related Ketone Oximes with Lithium Aluminium Hydride-3-O-cyclohexylmethyl-1,2-O-cyclohexylidene-α-D-glucofuranose Complex to give Optically Active Alcohols and Amines
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The asymmetric reduction of ketones and structurally related isoelectronic ketone oximes with lithium aluminium hydride-3-O-cyclohexylmethyl-1,2-O-cyclohexylidene-α-D-glucofuranose complex yields optically active alcohols of up to 42percent optical purity and optically active amines of up to 52percent optical purity, respectively.The resulting alcohols as well as amines all have the S-configuration.When the asymmetric reduction is carried out with the ethanol-modified glucofuranose complex, the resulting alcohols and amines have the R-configuration.
- Landor, Stephen R.,Chan, Yuet M.,Sonola, Olutunji O.,Tatchell, Austin R.
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p. 493 - 496
(2007/10/02)
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