- Single-Site Cobalt Catalysts at New Zr12(μ3-O)8(μ3-OH)8(μ2-OH)6 Metal-Organic Framework Nodes for Highly Active Hydrogenation of Nitroarenes, Nitriles, and Isocyanides
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We report here the synthesis of a robust and porous metal-organic framework (MOF), Zr12-TPDC, constructed from triphenyldicarboxylic acid (H2TPDC) and an unprecedented Zr12 secondary building unit (SBU): Zr12(μ3-O)8(μ3-OH)8(μ2-OH)6. The Zr12-SBU can be viewed as an inorganic node dimerized from two commonly observed Zr6 clusters via six μ2-OH groups. The metalation of Zr12-TPDC SBUs with CoCl2 followed by treatment with NaBEt3H afforded a highly active and reusable solid Zr12-TPDC-Co catalyst for the hydrogenation of nitroarenes, nitriles, and isocyanides to corresponding amines with excellent activity and selectivity. This work highlights the opportunity in designing novel MOF-supported single-site solid catalysts by tuning the electronic and steric properties of the SBUs.
- Ji, Pengfei,Manna, Kuntal,Lin, Zekai,Feng, Xuanyu,Urban, Ania,Song, Yang,Lin, Wenbin
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Read Online
- Deactivation mechanisms of iodo-iridium catalysts in chiral amine racemization
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The homogenous, [IrCp?I2]2, SCRAM catalyst (1) is active in the racemization of chiral amines. NMR, kinetic and structural mechanistic studies have determined the cause of catalyst deactivation to occur when ammonia or methylamine are liberated by hydrolysis or aminolysis of the intermediate imine, which tightly coordinate to the iridium centre to block turnover. Control of moisture and substrate concentration can suppress deactivation, whilst partial reactivation of spent catalyst was identified using hydroiodic acid.
- Kwan, Maria H.T.,Pokar, Nisha P.B.,Good, Catherine,Jones, Martin F.,Munday, Rachel,Screen, Thomas,Blacker, A. John
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supporting information
(2020/12/29)
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- Continuous Flow Chiral Amine Racemization Applied to Continuously Recirculating Dynamic Diastereomeric Crystallizations
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A new, dynamic diastereomeric crystallization method has been developed, in which the mother liquors are continuously separated, racemized over a fixed-bed catalyst, and recirculated to the crystallizer in a resolution-racemization-recycle (R3) process. S
- Kwan, Maria H. T.,Breen, Jessica,Bowden, Martin,Conway, Louis,Crossley, Ben,Jones, Martin F.,Munday, Rachel,Pokar, Nisha P. B.,Screen, Thomas,Blacker, A. John
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p. 2458 - 2473
(2021/02/06)
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- Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis
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Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening. An H-atom transfer, to generate a benzylic radical, serves as a radical translocation step, and an organometallic oxygen rebound as a reductive elimination. The reaction mechanism was studied by high-level dispersion corrected hybrid functional DFT with implicit solvation. The low-energy conformational space was searched by the efficient CREST program. The stereoselectivity was deduced from the lowest lying benzylic radical structures and their conformations are controlled by hyperconjugative interactions and steric interactions between the titanocene catalyst and the aryl groups of the substrate. An interesting mechanistic aspect is that the oxidation of the benzylic center occurs under reducing conditions.
- Funk, Pierre,Richrath, Ruben B.,Bohle, Fabian,Grimme, Stefan,Gans?uer, Andreas
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supporting information
p. 5482 - 5488
(2021/02/03)
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- CHIRALITY SENSING WITH MOLECULAR CLICK CHEMISTRY PROBES
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The present invention relates to an analytical method that includes providing a sample potentially containing a chiral analyte that can exist in stereoisomeric forms, and providing a probe selected from the group consisting of coumarin-derived Michael acceptors, dinitrofluoroarenes and analogs thereof, arylsulfonyl chlorides and analogs thereof, arylchlorophosphines and analogs thereof, aryl halophosphites, and halodiazaphosphites. The sample is contacted with the probe under conditions to permit covalent binding of the probe to the analyte, if present in the sample; and, based on any binding that occurs, the absolute configuration of the analyte in the sample, and/or the concentration of the analyte in the sample, and/or the enantiomeric composition of the analyte in the sample is/are determined. The probe may be a coumarin-derived Michael acceptor, a di nitrofluoroarene or analog thereof, an arylsulfonyl chloride or analog thereof, an arylchlorophosphine or analog thereof, an aryl halophosphite, or a halodiazaphosphite.
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Paragraph 0280; 0285-0286
(2020/02/23)
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- Tackling N-Alkyl Imines with 3d Metal Catalysis: Highly Enantioselective Iron-Catalyzed Synthesis of α-Chiral Amines
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A readily activated iron alkyl precatalyst effectively catalyzes the highly enantioselective hydroboration of N-alkyl imines. Employing a chiral bis(oxazolinylmethylidene)isoindoline pincer ligand, the asymmetric reduction of various acyclic N-alkyl imines provided the corresponding α-chiral amines in excellent yields and with up to >99 % ee. The applicability of this base metal catalytic system was further demonstrated with the synthesis of the pharmaceuticals Fendiline and Tecalcet.
- Blasius, Clemens K.,Gade, Lutz H.,Heinrich, Niklas F.,Vasilenko, Vladislav
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supporting information
p. 15974 - 15977
(2020/07/04)
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- Electrochemical, Iodine-Mediated α-CH Amination of Ketones by Umpolung of Silyl Enol Ethers
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The electrochemical, oxidative Umpolung reaction of silyl enol ethers utilizing simple iodide salts for the synthesis of α-amino ketones is described. The products were isolated in excellent yields of up to 100percent, and various functionalized starting materials were accepted in an undivided electrochemical cell design. Moreover, a sensitivity assessment to ensure an improved reproducibility of the reaction and cyclic voltammetry experiments were performed to postulate a plausible reaction mechanism on their basis.
- Strehl, Julia,Hilt, Gerhard
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supporting information
p. 5968 - 5972
(2020/08/12)
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- Selective synthesis of mono- and di-methylated amines using methanol and sodium azide as C1 and N1 sources
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A Ru(ii) complex mediated synthesis of various N,N-dimethyl and N-monomethyl amines from organic azides using methanol as a methylating agent is reported. This methodology was successfully applied for a one-pot reaction of bromide derivatives and sodium azide in methanol. Notably, by controlling the reaction time several N-monomethylated and N,N-dimethylated amines were synthesized selectively. The practical applicability of this tandem process was revealed by preparative scale reactions with different organic azides and synthesis of an anti-vertigo drug betahistine. Several kinetic experiments and DFT studies were carried out to understand the mechanism of this transformation.
- Chakrabarti, Kaushik,Mishra, Anju,Panja, Dibyajyoti,Paul, Bhaskar,Kundu, Sabuj
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supporting information
p. 3339 - 3345
(2018/07/29)
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- Photometric Characterization of the Reductive Amination Scope of the Imine Reductases from Streptomyces tsukubaensis and Streptomyces ipomoeae
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Imine reductases (IREDs) have emerged as promising enzymes for the asymmetric synthesis of secondary and tertiary amines starting from carbonyl substrates. Screening the substrate specificity of the reductive amination reaction is usually performed by time-consuming GC analytics. We found two highly active IREDs in our enzyme collection, IR-20 from Streptomyces tsukubaensis and IR-Sip from Streptomyces ipomoeae, that allowed a comprehensive substrate screening with a photometric NADPH assay. We screened 39 carbonyl substrates combined with 17 amines as nucleophiles. Activity data from 663 combinations provided a clear picture about substrate specificity and capabilities in the reductive amination of these enzymes. Besides aliphatic aldehydes, the IREDs accepted various cyclic (C4–C8) and acyclic ketones, preferentially with methylamine. IR-Sip also accepted a range of primary and secondary amines as nucleophiles. In biocatalytic reactions, IR-Sip converted (R)-3-methylcyclohexanone with dimethylamine or pyrrolidine with high diastereoselectivity (>94–96 % de). The nucleophile acceptor spectrum depended on the carbonyl substrate employed. The conversion of well-accepted substrates could also be detected if crude lysates were employed as the enzyme source.
- Matzel, Philipp,Krautschick, Lukas,H?hne, Matthias
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p. 2022 - 2027
(2017/10/07)
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- The kinetics and mechanism of the organo-iridium catalysed racemisation of amines
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The dimeric iodo-iridium complex [IrCp?I2]2 (Cp? = pentamethylcyclopentadiene) is an efficient catalyst for the racemisation of secondary and tertiary amines at ambient and higher temperatures with a low catalyst loading. The racemisation occurs with pseudo-first-order kinetics and the corresponding four rate constants were obtained by monitoring the time dependence of the concentrations of the (R) and (S) enantiomers starting with either pure (R) or (S) and show a first-order dependence on catalyst concentration. Low temperature 1H NMR data is consistent with the formation of a 1 : 1 complex with the amine coordinated to the iridium and with both iodide anions still bound to the metal-ion, but at the higher temperatures used for kinetic studies binding is weak and so no saturation zero-order kinetics are observed. A cross-over experiment with isotopically labelled amines demonstrates the intermediate formation of an imine which can dissociate from the iridium complex. Replacing the iodides in the catalyst by other ligands or having an amide substituent in Cp? results in a much less effective catalysts for the racemisation of amines. The rate constants for a deuterated amine yield a significant primary kinetic isotope effect kH/kD = 3.24 indicating that hydride transfer is involved in the rate-limiting step.
- Stirling, Matthew J.,Mwansa, Joseph M.,Sweeney, Gemma,Blacker, A. John,Page, Michael I.
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p. 7092 - 7098
(2016/07/30)
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- Asymmetric Reductive Amination of Ketones Catalyzed by Imine Reductases
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Biocatalysis employing imine reductases is a promising approach for the one-step generation of chiral amines from ketones. The enzymes reported for this process suffer from low activity and moderate stereoselectivity. We identified a set of enzymes that facilitate this reaction with high to quantitative conversions from a library of 28 imine reductases. This enabled the conversion of ketones with ammonia, methylamine, or butylamine into the corresponding amines. Most importantly, we performed preparative (>100 mg) scale syntheses of amines such as (1S,3R)-N,3-dimethylcyclohexylamine and (R)-N-methyl-2-aminohexane with excellent stereochemical purities (98 % de, 96 % ee) in good yields.
- Wetzl, Dennis,Gand, Martin,Ross, Alfred,Müller, Hubertus,Matzel, Philipp,Hanlon, Steven P.,Müller, Michael,Wirz, Beat,H?hne, Matthias,Iding, Hans
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p. 2023 - 2026
(2016/07/07)
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- Disulfonimide-Catalyzed Asymmetric Reduction of N-Alkyl Imines
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A chiral disulfonimide (DSI)-catalyzed asymmetric reduction of N-alkyl imines with Hantzsch esters as a hydrogen source in the presence of Boc2O has been developed. The reaction delivers Boc-protected N-alkyl amines with excellent yields and enantioselectivity. The method tolerates a large variety of alkyl amines, thus illustrating potential for a general reductive cross-coupling of ketones with diverse amines, and it was applied in the synthesis of the pharmaceuticals (S)-Rivastigmine, NPS R-568 Hydrochloride, and (R)-Fendiline. A chiral disulfonimide (DSI)-catalyzed asymmetric reduction of N-alkyl imines with Hantzsch esters as a hydrogen source in the presence of Boc2O was developed. The reaction delivers Boc-protected N-alkyl amines with excellent yields and enantioselectivity. The method was successfully applied to the synthesis of the pharmaceuticals (S)-Rivastigmine, NPS R-568 Hydrochloride, and (R)-Fendiline.
- Wakchaure, Vijay N.,Kaib, Philip S. J.,Leutzsch, Markus,List, Benjamin
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supporting information
p. 11852 - 11856
(2015/10/05)
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- Selective monomethylation of primary amines with simple electrophiles
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Direct monomethylation of primary amines with methyl triflate was achieved with high selectivity (up to 96%). The key point of this single methyl transfer stems from the use of HFIP as the solvent that interferes with amines and avoids overmethylation.
- Lebleu, Thomas,Ma, Xiaolu,Maddaluno, Jacques,Legros, Julien
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supporting information
p. 1836 - 1838
(2014/02/14)
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- "bridged" n →π* interactions can stabilize peptoid helices
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Peptoids are an increasingly important class of peptidomimetic foldamers comprised of N-alkylglycine units that have been successfully developed as antimicrobial agents, lung surfactant replacements, enzyme inhibitors, and catalysts, among many other applications. Since peptoid secondary structures can be crucial to their desired functions, significant efforts have been devoted to developing means of modularly controlling peptoid backbone amide cis-trans isomerism using side chains. Strategic engineering of interactions between side chain aromatic rings and backbone cis-amides (n→πAr interactions) is an attractive strategy for stabilizing helical structures in N-a-chiral aromatic peptoids, which are among the most utilized classes of structured peptoids. Herein, we report the first detailed computational and experimental study of n→πAr interactions in models of peptoids containing backbone thioamides, which we term "thiopeptoids". Our work has revealed that these interactions significantly affect amide rotamerism in both peptoid and thiopeptoid models via a newly characterized "bridged" mode of interaction mediated by the N-α-C-H σ orbitals. Overall, this work elucidates new strategies for controlling both peptoid and thiopeptoid folding and suggests that thiopeptoids will be highly structured and therefore potentially useful as therapeutics, biological probes, and nanostructural engineering elements.
- Gorske, Benjamin C.,Nelson, Ryan C.,Bowden, Zara S.,Kufe, Turner A.,Childs, Adam M.
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p. 11172 - 11183
(2013/12/04)
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- Highly active metal-free catalysts for hydrogenation of unsaturated nitrogen-containing compounds
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New highly active ansa-ammonium borate catalysts for the direct metal-free hydrogenation of imines were prepared by tuning of the basicity and steric bulkiness of their amine moieties. The highest catalytic activity among previously reported organocatalytic systems was shown for a wide range of nitrogen-containing substrates. The first example of asymmetric imine hydrogenation based on the ansa-ammonium borate concept was demonstrated. Furthermore, effective catalyst recovery by extraction of the acidic solution with an organic solvent followed by dehydration with TMSBr was elaborated. The initial findings highlight the development of more effective chiral ansa-ammonium borates for enantioselective hydrogenation. Therefore, the progress achieved in the ansa-ammonium borate concept makes it very promising for further elaboration with the aim to obtain industrially applicable catalysts. Copyright
- Sumerin, Victor,Chernichenko, Konstantin,Nieger, Martin,Leskelae, Markku,Rieger, Bernhard,Repo, Timo
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experimental part
p. 2093 - 2110
(2011/11/06)
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- Fast racemisation of chiral amines and alcohols by using cationic half-sandwich ruthena- and iridacycle catalysts
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The lipase-catalysed resolution of alcohols and amines yields only 50% of the desired enantiopure product. However, addition of a racemisation catalyst leads to 100% yield in what is called a dynamic kinetic resolution (DKR). There is a need for new racemisation catalysts that are fast and compatible with the conditions of the enzymatic reaction. We show that cationic half-sandwich ruthena- and iridacycle complexes are highly active and efficient in the racemisation of chiral alcohols and amines. Upon activation with base, these complexes are able to selectively racemise alcohols, whereas the non-activated complexes are selective catalysts for the racemisation of amines. We have applied the iridacycles in the DKR of racemic β-chloroalcohols to produce chiral epoxides in a biphasic system in good yields and high ee (ee = enantiomeric excess).
- Jerphagnon, Thomas,Gayet, Arnaud J.A.,Berthiol, Florian,Ritleng, Vincent,Mrsic, Natasa,Meetsma, Auke,Pfeffer, Michel,Minnaard, Adriaan J.,Feringa, Ben L.,De Vries, Johannes G.
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scheme or table
p. 12780 - 12790
(2010/06/16)
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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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- Molecular tweezers for hydrogen: Synthesis, characterization, and reactivity
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The first ansa-aminoborane N-TMPN-CH2C6H4B(C6F5)2 (where TMPNH is 2,2,6,6-tetramethylpiperidinyl) which is able to reversibly activate H2 through an intramolecular mechanism is synthesized. This new substance makes use of the concept of molecular tweezers where the active N and B centers are located close to each other so that one H2 molecule can fit in this void and be activated. Because of the fixed geometry of this ansa-ammonium-borate it forms a short N-H...H-B dihydrogen bond of 1.78 A as determined by X-ray analysis. Therefore, the bound hydrogen can be released above 100 °C. In addition, the short H...H contact and the N-H...H (154°) and B-H...H (125°) angles show that the dihydrogen interaction in N-TMPNH-CH2C6H4BH(C6F5)2 is partially covalent in nature. As a basis for discussing the mechanism, quantum chemical calculations are performed and it is found that the energy needed for splitting H2 can arise from the Coulomb attraction between the resulting ionic fragments, or "Coulomb pays for Heitler-London". The air- and moisture-stable N-TMPNH-CH2C6H4BH(C6F5)2 is employed in the catalytic reduction of nonsterically demanding imines and enamines under mild conditions (110 °C and 2 atm of H2) to give the corresponding amines in high yields. Copyright
- Sumerin, Victor,Schulz, Felix,Atsumi, Michiko,Wang, Cong,Nieger, Martin,Leskelae, Markku,Repo, Timo,Pyykkoe, Pekka,Rieger, Bernhard
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supporting information; experimental part
p. 14117 - 14119
(2009/03/11)
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- Chemoenzymatic dynamic kinetic resolution of secondary amines
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The kinetic resolution of amines using a novel iridium based catalyst coupled with an enzyme catalysed step is achieved on a large scale with high yields and ee.
- Stirling, Matthew,Blacker, John,Page, Michael I.
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p. 1247 - 1250
(2007/10/03)
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- Catalytic racemisation of chiral amines and application in dynamic kinetic resolution
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A mild and efficient procedure for the racemisation of optically active amines has been developed and applied to the dynamic kinetic resolution (DKR) of a racemic amine. Pentamethylcyclopentadienyliridium (III) iodide dimer dissolved in a convenient solvent is the precatalyst that reacts in situ with primary, secondary, or tertiary amines to form what we have named a SCRAM catalyst. This is able to dehydrogenate a substrate amine to form an imine, which, depending upon the reaction conditions, is then reduced back to the amine. When an optically active amine is mixed with the iridium precatalyst, racemisation is observed. The SCRAM catalyst is used under mild conditions compatible with suitable enzymes and acyl donors, and thus the DKR of an amine has been effected, giving significantly higher yield than if the enzyme alone was used. A mixed carbonate was identified as the optimal acyl donor, giving a carbamate product that is readily removed by acidic hydrolysis.
- Blacker, A. John,Stirling, Matthew J.,Page, Michael I.
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p. 642 - 648
(2012/12/31)
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- Mechanistic study of hydrogen transfer to imines from a hydroxycyclopentadienyl ruthenium hydride. Experimental support for a mechanism involving coordination of imine to ruthenium prior to hydrogen transfer
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Reaction of [2,3,4,5-Ph4(η5-C4COH) Ru(CO)2H] (2) with different imines afforded ruthenium amine complexes at low temperatures. At higher temperatures in the presence of 2, the complexes decomposed to give [RUsu
- Samec, Joseph S. M.,Ell, Alida H.,Aberg, Jenny B.,Privalov, Timofei,Eriksson, Lars,Baeckvall, Jan-E.
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p. 14293 - 14305
(2008/03/13)
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- Efficient N-p-methoxyphenyl amine deprotection through anodic oxidation
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A new method of deprotection of N-p-methoxyphenylamines using anodic oxidation in acidic medium is presented. The process furnishes a high yield of amine and is compatible with several oxidable functional groups.
- De Marin, Sandra Lamo,Martens, Thierry,Mioskowski, Charles,Royer, Jacques
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p. 10592 - 10595
(2007/10/03)
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- TACHYKININ RECEPTOR ANTAGONISTS
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The present invention relates to selective NK-1 receptor antagonists of Formula (I) or a pharmaceutically acceptable salt thereof, for the treatment of disorders associated with an excess of tachykinins.
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- Selective N-methylation of primary aliphatic amines with dimethyl carbonate in the presence of alkali cation exchanged Y-faujasites
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The N-methylation of aliphatic amines [XC6H4(CH 2)nNH2; n=1, X=H (1a), o-MeO (1b), p-MeO (1c); n=2, X=H (2a), o-MeO (2b); 1d: PhCH(Me)NH2] with dimethyl carbonate (DMC) is efficiently catalysed by NaY faujasite: on condition that CO 2 (a co-product of the reaction) is carefully removed, N-methyl- and N,N-dimethyl-amines (RNHMe and RNMe2) are obtained in good overall yields (70-90%). Otherwise, in the presence of CO2, carbamates (RNHCO2Me) form competitively to a large extent. The reaction probably proceeds through a BAl2 displacement of the amine on DMC.
- Selva, Maurizio,Tundo, Pietro
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p. 8139 - 8142
(2007/10/03)
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- Synthesis of N-methyl secondary amines
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A diverse set of N-methyl secondary amines are obtained in high yields by an expedient reductive alkylation of commercially available methanolic methylamine.
- Kumpaty, Hephzibah J.,Williamson, John S.,Bhattacharyya, Sukanta
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p. 1411 - 1416
(2007/10/03)
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- An efficient and mild ruthenium-catalyzed racemization of amines: Application to the synthesis of enantiomerically pure amines
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An efficient and mild Ru-catalyzed racemization of amines under transfer hydrogenation conditions is reported. A significant advantage of this new procedure is that the ruthenium hydrogen transfer catalysts allow high functional group tolerance. Interestingly, both primary and secondary amines were efficiently racemized under these conditions. We also report on the combination of this new amine racemization with an enzymatic kinetic resolution of primary amines.
- Pàmies, Oscar,éll, Alida H.,Samec, Joseph S.M.,Hermanns, Nina,B?ckvall, Jan-E.
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p. 4699 - 4702
(2007/10/03)
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- Pyrrolo[2,3-d]pyrimidine compounds
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A compound of the formula wherein R1, R2 and R3 are as defined above, which are inhibitors of the enzyme protein tyrosine kinases such as Janus Kinase 3 and as such are useful therapy as immunosuppressive agents for organ transplants, lupus, multiple sclerosis, rheumatoid arthritis, psoriasis, Type I diabetes and complications from diabetes, cancer, asthma, atopic dermatitis, autoimmune thyroid disorders, ulcerative colitis, Crohn's disease, Alzheimer's disease, Leukemia and other autoimmune diseases.
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- Gas-phase selective N-alkylation of amines with alcohols over γ- alumina
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Gas-phase conditions were successfully used for fine chemistry, in the N-alkylation of amines with alcohols as alkylating agents and γ-alumina as a catalyst. The method is also suitable for chiral compounds.
- Valot, Frederic,Fache, Fabienne,Jacquot, Roland,Spagnol, Michel,Lemaire, Marc
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p. 3689 - 3592
(2007/10/03)
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- Facile preparation of N-methyl secondary amines by titanium(IV) isopropoxide-mediated reductive animation of carbonyl compounds
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A simple, mild and efficient procedure for obtaining N-methyl secondary amines from aldehydes and ketones is reported. Treatment of carbonyl compounds with methylamine hydrochloride, triethylamine and titanium(IV) isopropoxide, followed by in situ sodium borohydride reduction and straightforward aqueous work-up, affords clean products in good to excellent yields.
- Neidigh, Kurt A.,Avery, Mitchell A.,Williamson, John S.,Bhattacharyya, Sukanta
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p. 2527 - 2531
(2007/10/03)
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- Organolanthanide-catalyzed imine hydrogenation. Scope, selectivity, mechanistic observations, and unusual byproducts
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In this paper we report the Cp'2LnMe2SiCp''2Ln-catalyzed (Cp' = η5-Me5C5; Cp'' = η5-Me4C5) hydrogenation of acyclic imines to yield the corresponding amines. At 190 psi of H2, the observed turnover frequencies (h-1) (100:1 substrate:catalyst ratio, Cp'2Ln, temperature (°C)) are (1) (N-benzylidene(methyl)amine, Ln = La, 50) 0.03; (Ln = Sm, 90) 1.0; (Ln = Sm + PhSiH3, 90) 2.2; (Ln = Lu, 90) 0.60; (2) (N-benzylideneaniline, Ln = Sm, 90) 0.10; (3) (N-benzylidene(trimethylsilyl)amine, Ln = Sm, 90) 0.40; (4) (N-(α-methylbenzylidene)(methyl)amine, Ln = Sm, 90) 0.20; (5) (N-(α-methylbenzylidene)(benzyl)amine, Ln = Sm, 90) 0.70. The stoichiometric reaction of N-benzylidene(methyl)amine with Cp'2SmCH(SiMe3)2 or (Cp'2SmH)2 yields an orthometalated Cp'2Sm-substrate complex which undergoes either hydrogenolysis/hydrogenation or competing C=N insertion of a second substrate molecule to yield a Cp'2Sm-imine-amido complex with a seven-membered chelate ring. The stoichiometric reaction of 2-methyl-1-pyrroline with Cp'2SmCH(SiMe3)2 or (Cp'2SmH)2 yields a Cp'2Sm-imine-amido complex in which two substrate molecules have been coupled to form a six-membered chelate ring (characterized by X-ray diffraction). The stoichiometric reaction of N-benzylidene(trimethylsilyl)amine with (Cp'2SmH)2 yields a desilylated Cp'2Sm-imine-amido complex with a four-membered Sm(NSiMe3)(CPh)N=CHPh chelate ring (characterized by X-ray diffraction). Additional heating of this product under H2 yields S6-symmetric (Cp'2SmCN)6, which contains an unusual chairlike 18-membered (SmCN)6 ring (characterized by X-ray diffraction).
- Obora, Yasushi,Ohta, Tetsuo,Stern, Charlotte L.,Marks, Tobin J.
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p. 3745 - 3755
(2007/10/03)
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- ELECTROCHEMICAL REDUCTIVE AMINATION. I. AMINATION OF ALIPHATIC KETONES BY PRIMARY AMINES
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The reductive amination of aliphatic ketones in aqueous solutions of primary amines was realized by an electrochemical method.The best yields of the secondary amines were obtained at lead and cadmium cathodes in an aqueous electrolytic solution at pH 11-12.Elongation and branching in the carbon chain of the radicals both of the ketone and of the primary amine lead to a reduction in the yield of the secondary amine.The yield of the secondary amine is mainly determined by the rate of the chemical reaction leading to the formation of the azomethine compound, preceding the electrochemical reduction stage.
- Smirnov, Yu. D.,Tomilov, A. P.
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- Deoxygenation of N,N-disubstituted hydroxylamines by carbon disulfide
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Hindered N,N-dialkylhydroxylamines react rapidly with CS2 to give the corresponding 2°-amines.
- Schwartz, Martin A.,Gu, Jiping,Hu, Xiufeng
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p. 1687 - 1688
(2007/10/02)
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- SYNTHESIS OF ARYLIMINES FROM N-SILYLAMIDES AND ARYLLITHIUM COMPOUNDS
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Various arylimines were synthesized by the addition of N-silylated-N-alkyl- or N-aryl-amides to aryllithium compounds.
- Feringa, Ben L.,Jansen, F. G. A.
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p. 507 - 508
(2007/10/02)
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- DERIVATIVES OF OPTICALLY ACTIVE (1-PHENYLETHYL)AMINE IN COMPLEXES WITH LITHIUM ALUMINUM HYDRIDE FOR THE ASYMMETRIC REDUCTION OF A CARBONYL GROUP
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(R)-1-Phenylethanol is formed preferentially in the reduction of acetophenone by the complexes of lithium aluminum hydride with (-)-(2-hydroxyethyl)(1-phenylethyl)amine and (-)-methyl(2-hydroxyethyl)(1-phenylmethyl)amine.
- Potapov, V. M.,Dem'yanovich, V. M.,Maleev, V. I.
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p. 1606 - 1609
(2007/10/02)
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- A NEW SYNTHESIS OF IMIDOYL IODIDES VIA BECKMANN REARRANGEMENT OF OXIME SULFONATES
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A new synthetic method of imidoyl iodides has been devised which involves the Beckmann rearrangement of oxime derivatives with trimethylsilyl iodide or diethylaluminum iodide.This allows a one-pot procedure for α-arylation of amines in synthetically usefu
- Ishida, Yasuko,Sasatani, Satoru,Maruoka, Keiji,Yamamoto, Hisashi
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p. 3255 - 3258
(2007/10/02)
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- Base Catalysed Rearrangements involving Ylide Intermediates. Part 18. Competing , , and Rearrangements of Ammonium Ylides
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The rearrangements of acyl stabilised ammonium ylides are, in several cases, accompanied by competing rearrangements and in one case by a rearrangement.For examples involving migrating benzyl or phenylethyl groups the mechanism of these rearrangements has been studied.Thus the competing , , and rearrangements of the ylide (12) are largely intramolecular, but the intermolecularity is as high as 28percent for the and rearrangements and 14percent for the rearrangement in methanol at 55 deg C.The competing and rearrangements of the optically active (29a) give products with predominant retention of the configuration of the migrating phenylethyl group, but the intramolecular stereoselectivity of the rearrangement is significantly greater than that of the rearrangement.These results are consistent with a radical pair pathway for all three modes of rearrangement.Suitably substituted acyl stabilised allylammonium ylides (55) rearrange by competing , and processes.
- Chantrapromma, Kan,Ollis, W. David,Sutherland, Ian O.
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p. 1049 - 1062
(2007/10/02)
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- Optically active imidazolidin-2-one derivatives
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A novel optically active cis-4,5-disubstituted imidazolidin-2-one derivative of the formula: STR1 wherein R1 is a C1 -C4 alkyl group or benzyl and R2 is a chiral aralkyl group optionally having at least one of C1 -C4 alkyl, C1 -C4 alkoxy and hydroxyl groups is produced asymmetrically by the reaction of 1,3-dibenzyl-cis-4,5-dicarboxy-imidazolidin-2-one or its anhydride with an optically active secondary amine of the formula: STR2 wherein R1 and R2 are each as defined above and is transformed into the lactone of 1,3-dibenzyl-cis-4-carboxy-5-hydroxymethyl-imidazolidin-2-one, which is a key intermediate in the synthesis of d-biotin.
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- STEREOCHEMICAL INVESTIGATIONS. LII. CHIRAL AMIDES OF o-HYDROXY- AND o-METHOXY-SUBSTITUTED BENZOIC ACIDS
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A number of o-hydroxy- and o-methoxybenzamides have been obtained from (-)-α-phenylamine, (+)-α-benzylethylamine, and (-)-1,2-diphenylethylamine, and their UV, IR, PMR, and CD spectra have been studied.The chiral optical properties of these amides are determined primarily by the nature of the cyclic structure which can form as a result of intramolecular hydrogen bonding.
- Solov'eva, L. D.,Dem'yanovich, V. M.,Potapov, V. M.
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p. 1099 - 1105
(2007/10/02)
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- Tetraalkylammonium Trihydridocyanoborates. Versatile, Selective Reagents for Reductive Aminations in Nonpolar Media
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Tetrabutylammonium cyanoborohydride or the combination of sodium cyanoborohydride with Aliquat 336 provides useful, convenient reagents for reductive amination of aldehydes and ketones in aprotic or protic media.
- Hutchins, Robert O.,Markowitz, Morris
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p. 3571 - 3574
(2007/10/02)
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