- One-pot reductive amination of carboxylic acids: a sustainable method for primary amine synthesis
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The reductive amination of carboxylic acids is a very green, efficient and sustainable method for the production of (bio-based) amines. However, with current technology, this reaction requires two to three reaction steps. Here, we report the first (heterogeneous) catalytic system for the one-pot reductive amination of carboxylic acids to amines, with solely H2 and NH3 as the reactants. This reaction can be performed with relatively cheap ruthenium-tungsten bimetallic catalysts in the green and benign solvent cyclopentyl methyl ether (CPME). Selectivities of up to 99% for the primary amine could be achieved at high conversions. Additionally, the catalyst is recyclable and tolerant for common impurities such as water and cations (e.g. sodium carboxylate).
- Coeck, Robin,De Vos, Dirk E.
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supporting information
p. 5105 - 5114
(2020/08/25)
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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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- Separate Sets of Mutations Enhance Activity and Substrate Scope of Amine Dehydrogenase
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Mutations were introduced into the leucine amine dehydrogenase (L-AmDH) derived from G. stearothermophilus leucine dehydrogenase (LeuDH) with the goals of increased activity and expanded substrate acceptance. A triple variant (L-AmDH-TV) including D32A, F101S, and C290V showed an average of 2.5-fold higher activity toward aliphatic ketones and an 8.0 °C increase in melting temperature. L-AmDH-TV did not show significant changes in relative activity for different substrates. In contrast, L39A, L39G, A112G, and T133G in varied combinations added to L-AmDH-TV changed the shape of the substrate binding pocket. L-AmDH-TV was not active on ketones larger than 2-hexanone. L39A and L39G enabled activity for straight-chain ketones as large as 2-decanone and in combination with A112G enabled activity toward longer branched ketones including 5-methyl-2-octanone.
- Franklin, Robert D.,Mount, Conner J.,Bommarius, Bettina R.,Bommarius, Andreas S.
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p. 2436 - 2439
(2020/04/16)
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- Chiral benzimidazole derived bis-phenyl triazoles as chiroptical sensors for iodide and chiral amines
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A series of chiral 2-hydroxy ethyl/benzyl benzimidazole based aryl triazole tweezers have been prepared using click chemistry in high yields. Chiral pool strategy has been used to obtain the benzimidazole-based tweezers in very high enantiomerically enriched form. The aryl triazole tweezers, S-(?)-5a and S-(+)-8a displayed a high degree of selectivity for iodide anion over other anions, including other halides. The aryl triazole tweezers, S-(?)-5a and S-(+)-8a display significant enantio-discrimination for chiral amines. The chiral recognition studies were carried out using UV and circular dichroism (CD) spectroscopy. NMR analysis has been used for establishing the sites for ligation of the iodide anion.
- John, Marina E.,Karnik, Anil V.
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supporting information
p. 2844 - 2853
(2020/05/25)
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- An Ammonium-Formate-Driven Trienzymatic Cascade for ω-Transaminase-Catalyzed (R)-Selective Amination
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(R)-Amination mediated by (R)-specific ω-transaminases generally requires costly d-alanine in excess to obtain the desired chiral amines in high yield. Herein, a one-pot, trienzymatic cascade comprising an (R)-specific ω-transaminase, an amine dehydrogenase, and a formate dehydrogenase was developed for the economical and eco-friendly synthesis of (R)-chiral amines. Using inexpensive ammonium formate as the sole sacrificial agent, the established cascade system enabled efficient ω-transaminase-mediated (R)-amination of various ketones, with high conversions and excellent ee (>99%); water and CO2 were the only waste products.
- Chen, Fei-Fei,Liu, Lei,Wu, Jian-Ping,Xu, Jian-He,Zhang, Yu-Hui,Zhang, Zhi-Jun,Zheng, Gao-Wei
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p. 14987 - 14993
(2019/12/02)
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- Rapid and Quantitative Profiling of Substrate Specificity of ω-Transaminases for Ketones
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ω-Transaminases (ω-TAs) have gained growing attention owing to their capability for asymmetric synthesis of chiral amines from ketones. Reliable high-throughput activity assay of ω-TAs is essential in carrying out extensive substrate profiling and establishing a robust screening platform. Here we report spectrophotometric and colorimetric methods enabling rapid quantitation of ω-TA activities toward ketones in a 96-well microplate format. The assay methods employ benzylamine, a reactive amino donor for ω-TAs, as a cosubstrate and exploit aldehyde dehydrogenase (ALDH) as a reporter enzyme, leading to formation of benzaldehyde detectable by ALDH owing to concomitant NADH generation. Spectrophotometric substrate profiling of two wild-type ω-TAs of opposite stereoselectivity was carried out at 340 nm with 22 ketones, revealing subtle differences in substrate specificities that were consistent with docking simulation results obtained with cognate amines. Colorimetric readout for naked eye detection of the ω-TA activity was also demonstrated by supplementing the assay mixture with color-developing reagents whose color reaction could be quantified at 580 nm. The colorimetric assay was applied to substrate profiling of an engineered ω-TA for 24 ketones, leading to rapid identification of reactive ketones. The ALDH-based assay is expected to be promising for high-throughput screening of enzyme collections and mutant libraries to fish out the best ω-TA candidate as well as to tailor enzyme properties for efficient amination of a target ketone.
- Han, Sang-Woo,Shin, Jong-Shik
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p. 3287 - 3295
(2019/06/21)
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- Asymmetric Amination of Secondary Alcohols by using a Redox-Neutral Two-Enzyme Cascade
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Multienzyme cascade approaches for the synthesis of optically pure molecules from simple achiral compounds are desired. Herein, a cofactor self-sufficient cascade protocol for the asymmetric amination of racemic secondary alcohols to the corresponding chiral amines was successfully constructed by employing an alcohol dehydrogenase and a newly developed amine dehydrogenase. The compatibility and the identical cofactor dependence of the two enzymes led to an ingenious in situ cofactor recycling system in the one-pot synthesis. The artificial redox-neutral cascade process allowed the transformation of racemic secondary alcohols into enantiopure amines with considerable conversions (up to 94 %) and >99 % enantiomeric excess at the expense of only ammonia; this method thus represents a concise and efficient route for the asymmetric synthesis of chiral amines. If you know what amine: A redox-neutral two-enzyme cascade encompassing an alcohol dehydrogenase (ADH) and an amine dehydrogenase (AmDH) is constructed for the synthesis of chiral amines from the corresponding racemic alcohols in one pot to afford considerable conversions (up to 94 %) and high enantiomeric excess values (>99 %) at the expense of only ammonia.
- Chen, Fei-Fei,Liu, You-Yan,Zheng, Gao-Wei,Xu, Jian-He
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p. 3838 - 3841
(2016/01/26)
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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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- Salts of (+)-deoxycholic acid with amines: Structure, thermal stability, kinetics of salt formation, decomposition and chiral resolution
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(+)-Deoxycholic acid forms salts with 1-propylamine, di-n-butylamine, sec-butylamine and 3-methyl-2-butylamine. The salts were characterised using thermal analysis and single crystal X-ray diffraction. The chiral discrimination of (+)-deoxycholic acid for racemic sec-butylamine and racemic 3-methyl-2-butylamine was studied and correlated with the structural and thermal results. A mixture of (+)-deoxycholic acid and racemic sec-butylamine yielded crystals of (R)-2-butylammonium deoxycholate. (+)-Deoxycholic acid was exposed to vapours of propylamine and racemic sec-butylamine and the kinetics of absorption were determined. The kinetics of decomposition of powdered samples obtained from (+)-deoxycholic acid with di-n-butylamine and racemic sec-butylamine were investigated. Crystallisation of (+)-deoxycholic acid with racemic 3-methyl-2-butylamine resulted in crystals of (S)-3-methyl-2- butylammonium deoxycholate.
- Jacobs, Ayesha,Bathori,Nassimbeni, Luigi R.,Sebogisi, Baganetsi K.
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p. 931 - 939
(2013/03/14)
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- Enantioselective benzoylation of racemic amines using chiral benzimidazolide as a benzoylating agent
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Enantioselective acylation/kinetic resolution of racemic amines has been achieved by using a chiral benzimidazolide, namely, (S)-1-benzoyl-2-(α-acetoxyethyl)benzimidazole 2. This nonenzymatic acylating reagent requires mild reaction conditions and proceeds with good enantioselectivity.
- Karnik, Anil V.,Kamath, Suchitra S.
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- Asymmetric reduction of ketoxime derivatives and N-alkylketimines with borane-oxazaborolidine adducts
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Oxime ethers of acetophenone, isopropyl methyl ketone, and tert-butyl methyl ketone were reduced to the corresponding hydroxylamine ethers of 45-94% ee with borane-oxazaborolidine 1 derived from (-)-norephedrine. A one-pot reduction of acetophenone oxime with 1 to 1-phenylethylhydroxylamine of 87% ee is described. The reduction of 6-methyl-2,3,4,5-tetrahydropyridine and N-methylimines of the above mentioned ketones with borane-B-methyloxazaborolidine adduct 2, derived from (-)-diphenylprolinol, gave the corresponding amines of 40-74% ee.
- Krzeminski, Marek P.,Zaidlewicz, Marek
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p. 1463 - 1466
(2007/10/03)
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- Diastereoselective addition of chiral aliphatic imines and 2-alkyl-1,3-oxazolidines to organometallic reagents
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The reaction of organocerium reagents with chiral aliphatic imines derived from (R)-O-methylphenylglycinol afforded the corresponding amines with high diastereoselectivity. In contrast, the reaction of Grignard reagents with chiral 2-alkyl-1,3-oxazolidines derived from (R)-N-methylphenylglycinol afforded the amines with changeover in diastereoselectivity.
- Higashiyama,Fujikura,Takahashi
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p. 722 - 728
(2007/10/02)
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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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- ORGANOBORANES FOR SYNTHESIS. 7. AN IMPROVED GENERAL SYNTHESIS OF PRIMARY AMINES FROM ALKENES via HYDROBORATION-ORGANOBORANE CHEMISTRY
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Triorganylboranes, R3B, and diorganylborinicesters, R2BOR', react readily with preformed chloramine or hydroxylamine-O-sulfonic acid to produce the corresponding primary amines, RNH2.However, the product of the reaction following hydrolysis is the boronic acid, RB(OH)2, limiting the yield to 67percent for R3B and to 50percent for R2BOR'.This problem has now been overcome with the help of lithium dimethylborohydride, readily converted in situ to dimethylborane.The hydroboration of representative alkenes by dimethylborane provides the corresponding monoorganyldimethylborane, RMe2B.Treatment of this intermediate with hydroxylamine-O-sulfonic acid provides the desired amines, RNH2, in isolated yields of 73percent to 95percent.The reaction proceeds with complete retention, reproducing the precise structure of the organic group in the organoboranes, RMe2B.
- Brown, Herbert C.,Kim, Kee-Won,Srebnik, Morris,Singaram, Bakthan
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p. 4071 - 4078
(2007/10/02)
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