- Enantioselective amination of α-phenyl-α-cyanoacetate catalyzed by chiral amines incorporating the α-phenylethyl auxiliary
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(Chemical Equation Presented) Nineteen chiral amines and their derivatives were prepared and investigated as organocatalytic Lewis bases in the α-amination of ethyl α-phenyl-α-cyanoacetate. For comparison purposes, a few natural products were also examine
- Liu, Yongjun,Melgar-Fernandez, Roberto,Juaristi, Eusebio
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Read Online
- BF3·Et2O as a metal-free catalyst for direct reductive amination of aldehydes with amines using formic acid as a reductant
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A versatile metal- and base-free direct reductive amination of aldehydes with amines using formic acid as a reductant under the catalysis of inexpensive BF3·Et2O has been developed. A wide range of primary and secondary amines and diversely substituted aldehydes are compatible with this transformation, allowing facile access to various secondary and tertiary amines in high yields with wide functional group tolerance. Moreover, the method is convenient for the late-stage functionalization of bioactive compounds and preparation of commercialized drug molecules and biologically relevant N-heterocycles. The procedure has the advantages of simple operation and workup and easy scale-up, and does not require dry conditions, an inert atmosphere or a water scavenger. Mechanistic studies reveal the involvement of imine activation by BF3and hydride transfer from formic acid.
- Fan, Qing-Hua,Liu, Xintong,Luo, Zhenli,Pan, Yixiao,Xu, Lijin,Yang, Ji,Yao, Zhen,Zhang, Xin
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supporting information
p. 5205 - 5211
(2021/07/29)
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- New chiral stationary phases for liquid chromatography based on small molecules: Development, enantioresolution evaluation and chiral recognition mechanisms
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Recently, we reported the development of new chiral stationary phases (CSPs) for liquid chromatography (LC) based on chiral derivatives of xanthones (CDXs). Based on the most promising CDX selectors, 12 new CSPs were successfully prepared starting from suitable functionalized small molecules including xanthone and benzophenone derivatives. The chiral selectors comprising one, two, three, or four chiral moieties were covalently bonded to a chromatographic support and further packed into LC stainless-steel columns (150?×?2.1?mm I.D.). The enantioselective performance of the new CSPs was evaluated by LC using different classes of chiral compounds. Specificity for enantioseparation of some CDXs was observed in the evaluation of the new CSPs. Besides, assessment of chiral recognition mechanisms was performed by computational studies using molecular docking approach, which are in accordance with the chromatographic parameters. X-Ray analysis was used to establish a chiral selector 3D structure.
- Phyo, Ye' Zaw,Teixeira, Joana,Tiritan, Maria Elizabeth,Cravo, Sara,Palmeira, Andreia,Gales, Luís,Silva, Artur M.S.,Pinto, Madalena M.M.,Kijjoa, Anake,Fernandes, Carla
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- CHIRAL CATALYST AND METHOD FOR ASYMMETRIC REDUCTION OF AN IMINE
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The present disclosure discusses (i) a compound having a chemical formula according to Formula (I), or its enantiomer; and (ii) a compound that is reactive with a hydride to produce a compound having a chemical formula according to Formula (I), or its enantiomer. Formula (I) is: Formula (I) where R1 and R2 are H, optionally substituted C1-C3 alkyl, or linked together to form an optionally substituted C3 or C4 alkyl group; R3 and R3' are H; R4 and R4' are the same, and are optionally substituted C1-C6 alkyl; and R5 and R5' are the same, and are optionally substituted aryl or heteroaryl. In some examples, R4 and R5 are linked, and R4' and R5' are linked, where both linking groups are the same. The present disclosure also discusses methods of asymmetric reduction of an imine, and methods of forming the catalysts and pre-catalysts.
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Paragraph 00116; 00117
(2019/04/16)
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- A new class of well-defined ruthenium catalysts for enantioselective transfer hydrogenation of various ketones
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A pair of novel optically pure phosphinite ligands were synthesized by ring opening reaction of chiral amines with (R)-styrene oxide or (S)-glycidyl phenyl ether oxide using a straightforward method in high yields and their ruthenium complexes were described in detail. The ruthenium complexes proved to be highly efficient catalysts for the enantioselective hydrogenation of ketones, affording products up to 99% ee. The results showed that the corresponding chiral alcohols could be obtained with high activity and excellent enantioselectivities at the desired temperature. (2S)-1-{benzyl[(1S)-1-(naphthalen-1-yl)ethyl]amino}-3-phenoxypropan-2-yl diphenylphosphinito[dichloro(η6-benzene)ruthenium (II)] acts an excellent catalyst in the reduction of ketones, giving the corresponding alcohol up to 99% ee.
- Kayan, Cezmi,Meri?, Nermin,Rafikova, Khadichakhan,Zazybin, Alexey,Gürbüz, Nevin,Karakaplan, Mehmet,Aydemir, Murat
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- Asymmetric Imine Hydroboration Catalyzed by Chiral Diazaphospholenes
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The first use of diazaphospholenes as chiral catalysts has been demonstrated with enantioselective imine hydroboration. A chiral diazaphospholene prepared in a simple three-step synthesis from commercial materials has been shown to achieve the highest enantioselectivity for the hydroboration of alkyl imines with pinacolborane reported to date. Enantiomer ratios of up to 88:12 were obtained with low (2 mol %) catalyst loadings. Twenty examples of asymmetric reduction employing this main-group catalysis protocol, including the synthesis of the pharmaceuticals ent-rasagiline and fendiline, are shown.
- Adams, Matt R.,Tien, Chieh-Hung,McDonald, Robert,Speed, Alexander W. H.
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p. 16660 - 16663
(2017/12/13)
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- An efficient catalytic reductive amination: A facile one-pot access to 1,2-dihydropyrrolo[3,4-b]indol-3(4H)-ones by using B(C 6 F 5 ) 3 /NaBH 4
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An efficient combination of B(C6F5)3 and NaBH4 was developed for direct reductive amination of aldehydes. A wide range of functional groups such as ester, nitro, nitrile, halogen, alkene, heterocycles were tolerated. Also, acid sensitive protecting groups like TBDMS and TBDPS were not affected. In addition, the present methodology was extended for tandem amination-amidation of 3-formyl-indole-2-carboxylic acids with substituted anilines to afford 1,2-dihydropyrrolo[3,4-b]indol-3(4H)-ones. [Figure not available: see fulltext.]
- Nagarsenkar, Atulya,Prajapti, Santosh Kumar,Babu, Bathini Nagendra
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p. 711 - 716
(2015/06/17)
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- Dehydrogenative synthesis of imines from alcohols and amines catalyzed by a ruthenium N-heterocyclic carbene complex
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A new method for the direct synthesis of imines from alcohols and amines is described where hydrogen gas is liberated. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex [RuCl2(IiPr)(p-cymene)] in the presence of the ligand DABCO and molecular sieves. The imination can be applied to a variety of primary alcohols and amines and can be combined with a subsequent addition reaction. A deuterium labeling experiment indicates that the catalytically active species is a ruthenium dihydride. The reaction is believed to proceed by initial dehydrogenation of the alcohol to the aldehyde, which stays coordinated to ruthenium. Nucleophilic attack of the amine affords the hemiaminal, which is released from ruthenium and converted into the imine.
- Maggi, Agnese,Madsen, Robert
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experimental part
p. 451 - 455
(2012/04/23)
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- Iron triflate catalyzed reductive amination of aldehydes using sodium borohydride
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An efficient and convenient procedure for the reductive amination of aldehydes using NaBH4 in the presence of catalytic amount of Fe(OTf)3 is described.
- Uday Kumar,Sudhakar Reddy,Prabhakar Reddy,Bandichhor, Rakeshwar
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supporting information; experimental part
p. 4354 - 4356
(2012/10/08)
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- Method For The Preparation Of Cinacalcet And Intermediates And Impurities Thereof
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A method for the preparation of Cinacalcet is disclosed comprising treating (R)-1-naphthyl ethylamine with an aromatic aldehyde to form (1R)-1-(2-naphthyl)-N-(aryl methylene)ethanamine derivative of Formula (IV), which is further treated with 1-(3-halopropyl)-3-(trifluoromethyl)benzene of Formula (V) to obtain an iminium salt of Formula (VI), followed by hydrolysis to obtain Cinacalcet free base.
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Page/Page column 18-19
(2012/01/13)
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- Industrial application of the forster reaction: Novel one-pot synthesis of cinacalcet hydrochloride, a calcimimetic agent
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Described is a new, practical, and one-pot process, based on the Forster reaction, for the synthesis of cinacalcet hydrochloride (1), a calcimimetic agent and calcium-sensing receptor antagonist. The synthesis comprises the condensation of (1R)-(+)-1-naphthylethyl amine (2) with benzaldehyde (3) followed by reaction of obtained Schiff's base 4 with 1-(3-halopropyl)-3- (trifluoromethyl)benzene (5) to provide highly unstable iminium salt 6. Subsequent hydrolysis of 6 with water in the same pot yielded cinacalcet. The treatment of cinacalcet with hydrochloric acid during the workup process furnished 1 with an overall yield of around 60%. Our synthetic approach for 1, discussed in this report demonstrates industrial application of the century-old, unexplored name reaction, "Forster's Reaction" or Forster-Decker synthesis.
- Shinde, Gorakshanath B.,Niphade, Navnath C.,Deshmukh, Shrikant P.,Toche, Raghunath B.,Mathad, Vijayavitthal T.
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experimental part
p. 455 - 461
(2012/05/19)
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- Efficient, selective, and green: Catalyst tuning for highly enatioselective reactions of ethylene
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Fine tuning of the biaryl and amino moieties of Feringa's phosphoramidite ligands yields structurally simpler, yet more efficient and selective, ligands for asymmetric hydrovinylation of vinylarenes and acylic 1,3-dienes. The enantioselectivities and yields observed in the formation of the 3-arylbutenes are among the highest for all asymmetric catalytic processes reported to date for the synthesis of intermediates for the widely used antiinflammatory 2-arylpropionic acids including naproxen, ibuprofen, fenoprofen, and flurbiprofen.
- Smith, Craig R.,Rajanbabu
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supporting information; experimental part
p. 1657 - 1659
(2009/04/10)
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- Enantioselective hydrogenation of ethyl pyruvate over Pt/alumina modified by (R)-1-(1-naphthyl)ethylamine derivatives
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A new chiral modifier, (R)-1-(1-naphthyl)ethylamine, has been tested in the enantioselective hydrogenation of ethyl pyruvate to ethyl lactate over 5 wt% Pt/Al2O3. The influence of catalyst (2-28 g liter-1) and modifier concentration (0-20 mM), temperature (282-333 K), pressure (1-75 bar), and solvents was studied in a slurry reactor. The 82% enantiomeric excess (ee) at full conversion was achieved in acetic acid after optimizing the reaction parameters. Under mild conditions the new modifier affords ee's better than that achieved with cinchona alkaloids. A drop in ee at pressures higher than 10 bar and temperatures above 288 K is attributed to partial hydrogenation of the naphthalene ring, which hinders the adsorption of the modifier parallel to a flat Pt surface. Maximum rate acceleration by a factor of 12, compared to the racemic reaction, was observed after thermal treatment of the catalyst in flowing hydrogen at 673 K, followed by aerobic treatment at 273-298 K in acetic acid. It is shown that naphthylethylamine is only a precursor of the actual modifier, which is a secondary amine formed in situ from naphthylethylamine and ethyl pyruvate by condensation to the corresponding imine and subsequent reduction of the C=N bond. Several other derivatives of naphthylethylamine were prepared by reductive alkylation and tested as modifiers. The results indicate that the presence of an oxygen function such as a hydroxy or methoxy group, as in previously used modifiers, is not an indispensable requirement for obtaining high ee in the hydrogenation of α-ketoesters.
- Minder,Schueren,Mallat,Baiker,Heinz,Pfaltz
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p. 261 - 268
(2007/10/03)
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- 1-(1-Naphthyl)ethylamine and Derivatives thereof as Chiral Modifiers in the Enantioselective Hydrogenation of Ethyl Pyruvate over Pt-Alumina
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Catalytic quantities of (R)- or (S)-1-(1-naphthyl)ethylamine induce up to 82percent e.e. in the hydrogenation of ethyl pyruvate over Pt-alumina, the actual modifier responsible for enantioselection being the secondary amine resulting from imine formation
- Heinz, Thomas,Wang, Guozhi,Pfaltz, Andreas,Minder, Bruno,Schuerch, Markus,et al.
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p. 1421 - 1422
(2007/10/02)
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