- Why Does the Intramolecular Trimethylene-Bridged Frustrated Lewis Pair Mes2PCH2CH2CH2B(C6F5)2 Not Activate Dihydrogen?
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The methyl labelled C3-bridged frustrated phosphane borane Lewis pair (P/B FLP) 2 b was prepared by treatment of Mes2PCl with a methallyl Grignard reagent followed by anti-Markovnikov hydroboration with Piers' borane [HB(C6/sub
- ?zgün, Thomas,Ye, Ke-Yin,Daniliuc, Constantin G.,Wibbeling, Birgit,Liu, Lei,Grimme, Stefan,Kehr, Gerald,Erker, Gerhard
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Read Online
- EPR and ENDOR Study of Chiral Nitroxides
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Racemic and achiral alkyl aryl nitroxides were examined at various temperatures.The restricted rotation of the aminoxyl substituents was indicated both by the β-proton coupling constants and by the inequivalence of the aromatic ortho protons.These results
- Stegmann, Hartmut B.,Schaber, Frank-Martin,Schuler, Paul,Scheffler, Klaus
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Read Online
- A new pathway for hydroamination. Mechanism of palladium-catalyzed addition of anilines to vinylarenes
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The mechanism of the hydroamination of vinylarenes with anilines catalyzed by phosphine-ligated palladium triflates was uncovered. η3-Arylethyl diphosphine palladium triflate complexes, which result from migratory insertion of vinylarene into a
- Nettekoven, Ulrike,Hartwig, John F.
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Read Online
- Iron-catalysed hydroboration of non-activated imines and nitriles: Kinetic and mechanistic studies
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Iron-catalysed hydroboration of imines and nitriles has been developed under low catalyst loading (1 mol%) in the presence of HBpin. A wide scope of substrate was found to smoothly undergo hydroboration, including electron releasing/withdrawing and haloge
- Bazkiaei, Adineh Rezaei,Wiseman, Michael,Findlater, Michael
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p. 15284 - 15289
(2021/05/19)
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- Ruthenium N-Heterocyclic Carbene Complexes for Chemoselective Reduction of Imines and Reductive Amination of Aldehydes and Ketones
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Chemoselective reduction of imines to secondary amines is catalyzed efficiently by tethered and untethered, half-sandwich ruthenium N-heterocyclic carbene (NHC) complexes at room temperature. The untethered Ru-NHC complexes are more efficient as catalysts for the reduction of aldimines and ketimines than the tethered complexes. Using the best untethered complex as a catalyst, electronic and steric demands on the reaction was probed using a series of imines. Chemoselectivity of the catalyst towards imine reduction was tested by performing inter and intramolecular competitive reactions in a variety of ways. The catalyst exhibits a very high TON and TOF under anaerobic conditions.
- Kathuria, Lakshay,Samuelson, Ashoka G.
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supporting information
(2020/06/17)
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- Lithium bromide: an inexpensive and efficient catalyst for imine hydroboration with pinacolborane at room temperature
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An efficient protocol for the hydroboration of imines is reported. Lithium halide salts are effective catalysts to convert aldimines and ketimines to their corresponding amines. Here, we report excellent isolated yield of secondary amines (>95%) using 3 mol% lithium bromide in THF at room temperature. In addition, DFT calculations for a plausible reaction pathway are reported.
- An, Duk Keun,Hwang, Hyonseok,Kim, Hanbi,Kim, Hyun Tae,Lee, Ji Hye
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p. 34421 - 34427
(2020/10/12)
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- B(C6F5)3-catalyzed transfer hydrogenations of imines with Hantzsch esters
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Highly efficient transfer hydrogenations of imines were realized with as low as 0.1 mol% of B(C6F5)3 by using Hantzsch esters as a hydrogen source, furnishing a variety of amines in 80-99% yields. For the asymmetric transf
- Wang, Qiaotian,Chen, Jingjing,Feng, Xiangqing,Du, Haifeng
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supporting information
p. 1448 - 1451
(2018/03/08)
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- Cyclometalated Half-Sandwich Iridium Complex for Catalytic Hydrogenation of Imines and Quinolines
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Several C,N-chelate cyclometalated half-sandwich iridium-based catalysts for imines and quinoline derivatives reduction have been prepared through metal-mediated C-H bond activation based on benzothiazole ligands. These iridium complexes exhibited high catalytic activity for hydrogenation of various types of imines with high yields. The most active catalyst was obtained from methoxyl substituted complex 2, showing the catalytic TOF value of 975 h-1 for the reduction of imine 6a. Additionally, these half-sandwich complexes also showed high efficiency for the catalytic hydrogenation of N-heterocyclic quinoline derivatives. Good catalytic activity was displayed for various kinds of substrates with either electron-donating or electron-withdrawing groups. Complexes 1-5 were fully characterized by NMR, IR, and elemental analysis. Molecular structures of complexes 1 and 4 were further confirmed by X-ray diffraction analysis.
- Yao, Zi-Jian,Lin, Nan,Qiao, Xin-Chao,Zhu, Jing-Wei,Deng, Wei
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p. 3883 - 3892
(2018/11/24)
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- Phosphine ligand compounds based on tetramethylspirobiindane skeleton, intermediate of compounds, and preparation method and application of compounds
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The invention discloses phosphine ligand compounds based on a tetramethylspirobiindane skeleton, an intermediate of the compounds, and a preparation method and application of the compounds. The phosphine ligand compounds are compounds having a structure r
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Paragraph 0172; 0174; 0175; 0176; 0177
(2018/11/03)
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- A Ferrocene-Based Phosphane/Borane Frustrated Lewis Pair for Asymmetric Imine Reduction
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The α-phosphanylferrocenecarbaldehyde (pS)-1 was converted into the β-styryl derivative (pS)-4 by Wittig–Horner olefination. Subsequent hydroboration with Piers' borane [HB(C6F5)2] followed by H2splitting and cr
- Ye, Ke-Yin,Wang, Xiaowu,Daniliuc, Constantin G.,Kehr, Gerald,Erker, Gerhard
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supporting information
p. 368 - 371
(2017/02/05)
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- Decrypting Transition States by Light: Photoisomerization as a Mechanistic Tool in Br?nsted Acid Catalysis
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Despite the wide applicability of enantioselective Br?nsted acid catalysis, experimental insight into transition states is very rare, and most of the mechanistic knowledge is gained by theoretical calculations. Here, we present an alternative approach (de
- Renzi, Polyssena,Hioe, Johnny,Gschwind, Ruth M.
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supporting information
p. 6752 - 6760
(2017/05/29)
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- BArF3-Catalyzed Imine Hydroboration with Pinacolborane Not Requiring the Assistance of an Additional Lewis Base
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The rarely used boron Lewis acid tris[3,5-bis(trifluoromethyl)phenyl]borane (BArF3) is found to be an excellent catalyst for metal-free hydroboration of imines. In the presence of 1.0 mol % of BArF3, several ketimines and aldimines undergo hydroboration with pinacolborane (HBpin) at room temperature without the aid of an external Lewis base. BArF3 is more reactive than other Lewis acidic boranes, including the often-used tris(pentafluorophenyl)borane (B(C6F5)3). The steric hindrance imparted by the six fluorine atoms ortho to the boron center in B(C6F5)3 accounts for this. Mechanistic control experiments indicate conventional Lewis acid catalysis involving imine activation and hydride transfer from HBpin.
- Yin, Qin,Soltani, Yashar,Melen, Rebecca L.,Oestreich, Martin
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supporting information
p. 2381 - 2384
(2017/07/17)
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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 formula: (Formula (I)) where ring B is a conjugated ring system with one or more substituents. The catalysts of the invention are particularly effective in reductive amination procedures which involve the in situ generation of the imine or iminium under reductive hydrogenative conditions.
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Paragraph 0293; 0295
(2015/03/16)
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- Metal-free catalytic hydrogenation of imines with recyclable [2.2]paracyclophane-derived frustrated lewis pairs catalysts
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A series of [2.2]paracyclophane-derived frustrated Lewis pairs (FLPs) with reversible, metal-free hydrogen activation was synthesized and successfully applied in the hydrogenation of imines in moderate to good yields. The high stability of the novel FLP system enables effective recycling of the metal-free catalysts. This reaction could also be compatible with a larger scale and developed into a pharmaceutical synthesis of cinacalcet {(R)-N-[1-(1-naphthyl) ethyl]-3-[3-(trifluoromethyl)phenyl]propan-1-amine} without heavy metal residues.
- Wang, Guan,Chen, Cheng,Du, Tieqi,Zhong, Weihui
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supporting information
p. 1747 - 1752
(2014/06/09)
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- A highly active cyclometallated iridium catalyst for the hydrogenation of imines
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A cyclometallated iridium complex containing an imino ligand has been shown to catalyse the hydrogenation of imines. The catalyst is highly active and selective for imino bonds, with a wide variety of imines being hydrogenated in less than 1 hour at a substrate/catalyst (S/C) ratio of 2000 at 20 bar H 2 pressure and 75 °C.
- Villa-Marcos, Barbara,Tang, Weijun,Wu, Xiaofeng,Xiao, Jianliang
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supporting information
p. 6934 - 6939
(2013/10/08)
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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 formula: (Formula (I)) where ring B is a conjugated ring system with one or more substituents. The catalysts of the invention are particularly effective in reductive amination procedures which involve the in situ generation of the imine or iminium under reductive hydrogenative conditions.
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Paragraph 00137; 00139
(2013/11/05)
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- N-Alkylation of amines with alcohols over nanosized zeolite beta
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Direct N-alkylation of amines with alcohols was successfully performed by using nanosized zeolite beta, which showed the highest catalytic activity among other conventional zeolites. This method has several advantages, such as eco-friendliness, moderate to high yields, and simple work-up procedure. The catalyst was successfully recovered and reused without significant loss of activity and only water is produced as co-product. In addition, imines were also efficiently prepared from the tandem reactions of amines with 2-, 3- and 4-nitrobenzyl alcohols using nanosized zeolite beta.
- Reddy, Marri Mahender,Kumar, Macharla Arun,Swamy, Peraka,Naresh, Mameda,Srujana, Kodumuri,Satyanarayana, Lanka,Venugopal, Akula,Narender, Nama
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supporting information
p. 3474 - 3483
(2013/12/04)
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- Palladium-catalyzed substitution and cross-coupling of benzylic fluorides
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Benzylic fluorides are suitable substrates for Pd(0)-catalyzed Tsuji-Trost substitution using carbon, nitrogen, oxygen, and sulfur nucleophiles and for cross-coupling with phenylboronic acid. For the bifunctional substrate 4-chlorobenzyl fluoride, fine-tuning of the reaction conditions allows for the regioselective displacement of either the chlorine or fluorine substituent. The leaving group ability of fluoride vs other groups displaced in substitution is CF3CO2 ≈ p-NO2C6H 4CO2 ≈ OCO2CH3 > F > CH3CO2, a ranking similar to allylic fluorides under Pd catalysis.
- Blessley, George,Holden, Patrick,Walker, Matthew,Brown, John M.,Gouverneur, Veronique
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p. 2754 - 2757
(2012/07/16)
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- Trifluoromethanesulfonic acid as an efficient catalyst in the reduction of ketimines
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Trifluoromethanesulfonic acid was found to be highly efficient catalyst in the reduction of ketimines with Hantzsh esters as the hydrogen source. The catalyst loading could be decreased to 1 mol %. Moderate to excellent isolated yields (up to 99 %) were obtained under mild conditions.
- Li, Jianhui,Wang, Zhouyu,Jiang, Zhenju,Jiang, Shengqian
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p. 3101 - 3103
(2012/01/06)
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- Thieme chemistry journal awardees - Where are they now? Asymmetric br?nsted acid catalyzed transfer hydrogenations
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Asymmetric hydrogenations are of great importance in the synthesis of optically active amines. This account highlights the development of the first metal-free transfer hydrogenation that is both highly enantioselective and inspired by natures dehydrogen?ase. Further focus is given to the extension of this bioinspired process to provide a variety of valuable, biologically active products and natural products under mild reaction conditions. Georg Thieme Verlag Stuttgart - New York.
- Rueping, Magnus,Sugiono, Erli,Schoepke, Fenja R.
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scheme or table
p. 852 - 865
(2010/07/06)
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- Chiral organic catalysts for the stereoselective reduction of carbon-nitrogen double bonds for the preparation of enantiomerically enriched amines
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The invention relates to compounds of general formula (I): wherein R1-R7 are as defined in the description for use as catalysts in the stereoselective reduction of imines in the presence of trichlorosilane as reducing agent.
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Page/Page column 9; 13-14
(2009/06/27)
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- Nucleophilic substitution reactions of alcohols with use of montmorillonite catalysts as solid Bronsted acids
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(Chemical Equation Presented) We have developed an environmentally benign synthetic approach to nucleophilic substitution reactions of alcohols that minimizes or eliminates the formation of byproducts, resulting in a highly atom-efficient chemical process. Proton- and metal-exchanged montmorillonites (H- and Mn+-mont) were prepared easily by treating Na +-mont with an aqueous solution of hydrogen chloride or metal salt, respectively. The H-mont possessed outstanding catalytic activity for nucleophilic substitution reactions of a variety of alcohols with anilines, because the unique acidity of the H-mont catalyst effectively prevents the neutralization by the basic anilines. In addition, amides, indoles, 1,3-dicarbonyl compounds, and allylsilane act as nucleophiles for the H-mont-catalyzed substitutions of alcohols, which allowed efficient formation of various C-N and C-C bonds. The solid H-mont was reusable without any appreciable loss in its catalytic activity and selectivity. Especially, an Al3+-mont showed high catalytic activity for the α-benzylation of 1,3-dicarbonyl compounds with primary alcohols due to cooperative catalysis between a protonic acid site and a Lewis acidic Al3+ species in its interlayer spaces.
- Motokura, Ken,Nakagiri, Nobuaki,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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p. 6006 - 6015
(2008/02/10)
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- Relative rates for the amination of η3-allyl and η3-benzyl complexes of palladium
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Reactions of nucleophiles with metal-bound hydrocarbyl π-ligands bound in an η3-fashion are key steps in a variety of carbon-carbon and carbon-heteroatom bond-forming reactions. To reveal factors that control the rates of reaction of nucleophiles with this type of ligand, the rates of reactions of an aromatic and an aliphatic amine with a series of η3-allyl, η3-benzyl, and η3-phenethyl palladium complexes ligated by the bisphosphine (R)-BINAP to form allylic and benzylic amines were measured. These data showed that the less common addition to an η3-benzyl complex is faster than the more common addition to an η3-allyl complex. The relative rates of reaction followed the trend naphthylmethyl > naphthylethyl > benzyl > 1,1-dimethylallyl > allyl. Computational studies suggest that there is a correlation between the amount of positive charge at the site of nucleophilic attack and the rate of C-N bond formation. Copyright
- Johns, Adam M.,Tye, Jesse W.,Hartwig, John F.
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p. 16010 - 16011
(2007/10/03)
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- Direct measurement of the thermodynamics of vinylarene hydroamination
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The thermodynamics for intermolecular hydroamination of vinylarenes with arylamines have been measured directly by conducting the addition processes, as well as cleavage of the addition products, under conditions in which amine, vinylarene, and phenethylamine are all present. The reaction of N-methylaniline with styrene is exothermic by about 10 kcal/mol but nearly thermoneutral in free energy. The free energies for additions of various primary arylamines to styrene and for additions of primary arylamines to indene, dihydronaphthalene, and two vinylarenes range from 1.3 to -3.5 kcal/mol (K = 0.16-155 M-1). The steric properties of the nucleophile significantly influenced the equilibrium constant for addition, but the electronic properties of the nucleophile had a minor effect on this equilibrium constant. These measurements have led to the first successful intermolecular addition of aniline to indene and 1,2-dihydronaphthalene and shed light on factors requiring consideration when choosing substrates and reaction conditions for this transformation. Copyright
- Johns, Adam M.,Sakai, Norio,Ridder, Andre,Hartwig, John F.
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p. 9306 - 9307
(2007/10/03)
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- RUTHENIUM-CATALYZED HYDROAMINATION OF OLEFINS
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Applicants have unexpectedly discovered that catalysts made from a ruthenium catalyst precursor or preformed ruthenium catalysts as otherwise described in the present specification are capable of effecting the addition of a N-H bond across an olefin C=C (olefinic) bond of a substrate with a high degree of regioselectivity and enantioselectivity in high yield. These addition reactions proceed in an anti-Markovnikov or Markovnikov fashion depending upon the catalyst precursor used to generate the ruthenium catalyst which actually participates in the addition reaction. The present invention relates to methods of adding N-H bonds across an olefinic bond in a substrate, using a ruthenium catalyst precursor or catalyst I comprising a compound according to the general structure I: Formula (I) where Ru is a ruthenium atom; L1 represents one or more coordinated ancillary ligands, which may be all the same ligand or which may be a combination of different ligands, each of which may be neutral or formally charged, and each of which may be monodentate and coordinated to ruthenium through a single atom or which may be linked or chelated and bound through more than one atom; L2 represents one or more formally charged ligands which are the same or different and which are optionally susceptible to removal with a strong acid; and x is 0-6, preferably 1, y is 0-6, preferably 2 and n is 1-4, preferably 1.
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Page/Page column 27-28
(2010/02/13)
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- Air- and moisture-stable cationic (diphosphine)palladium(II) complexes as hydroamination catalysts X-ray crystal structures of two complexes
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A series of cationic (diphosphine)palladium(II) complexes have been prepared and fully characterized, including two crystal structures. These complexes were evaluated as catalysts for the hydroamination of acyclic alkenes. The reactivity of the catalysts is dependent on the nature of the diphosphine ligand and the substituents on the amine and alkene substrates.
- Li, Kelin,Horton, Peter N.,Hursthouse, Michael B.,Hii, King Kuok Mimi
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p. 250 - 257
(2007/10/03)
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- Ruthenium-catalyzed transfer hydrogenation of imines by propan-2-ol in benzene
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Transfer hydrogenation of a variety of different imines to the corresponding amines by propan-2-ol in benzene catalyzed by [Ru2(CO)4(μ H)(C4Ph4COHOCC4Ph4)] (1) has been studied. The reaction is highly efficient with turnover frequencies of over 800 per hour, and the product amines were obtained in excellent yields. A remarkable concentration dependence of propan-2-ol was observed when the reaction was run in benzene as cosolvent. An optimum was obtained at 24 equivalents of propan-2-ol to imine, and further increase of the propan-2-ol led to a dramatic decrease in rate. Also the use of polar cosolvents with 24 equivalents of propan-2-ol gave a low rate. It was found that ketimines react faster than aldimines and that electron-donating substituents on the imine increase the rate of the catalytic transfer hydrogenation. Electron-withdrawing substituents decreased the rate. An isomerization was observed with imines having an α-hydrogen at the N-alkyl substituent, which is in accordance with a mechanism involving a ruthenium-amine intermediate. It was demonstrated that the ruthenium-amine complex from α-methylbenzylamine, corresponding to the postulated intermediate, can replace 1 as catalyst in the transfer hydrogenation of imines. A primary deuterium isotope effect of kCH/CD = 2.7 ± 0.25 was observed when 2-deuterio-propan-2-ol vas used in place of propan-2-ol in the ransfer hydrogenation of N-phenyl-(1-phenylethylidene)amine.
- Samec, Joseph S. M.,Baeckvall, Jan-E.
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p. 2955 - 2961
(2007/10/03)
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- Transition metal-catalyzed process for addition of amines to carbon-carbon double bonds
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The present invention is directed to a process for addition of amines to carbon-carbon double bonds in a substrate, comprising: reacting an amine with a compound containing at least one carbon-carbon double bond in the presence a transition metal catalyst under reaction conditions effective to form a product having a covalent bond between the amine and a carbon atom of the former carbon-carbon double bond. The transition metal catalyst comprises a Group 8 metal and a ligand containing one or more 2-electron donor atoms. The present invention is also directed to enantioselective reactions of amine compounds with compounds containing carbon-carbon double bonds, and a calorimetric assay to evaluate potential catalysts in these reactions.
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- First chemo- and stereoselective reduction of imines using trichlorosilane activated with N-formylpyrrolidine derivatives
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Trichlorosilane activated with N-formylpyrrolidine derivatives was found to be an effective reagent for reduction of imines to amines. The reagent showed much higher selectivity toward imino groups than carbonyl groups. The reduction of imines using trichlorosilane activated with optically active N-formylproline derivatives gave enantiomerically enriched amines in moderate optical yields (up to 66% ee).
- Iwasaki, Fumiaki,Onomura, Osamu,Mishima, Katsuhiko,Kanematsu, Takefumi,Maki, Toshihide,Matsumura, Yoshihiro
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p. 2525 - 2527
(2007/10/03)
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- Design and Development of New Chemical Reactions via Low-valent Titanium-induced Cleavage of Carbon - Heteroatom Bonds
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Low-valent titanium (LVT)-induced regioselective cleavage of N-arylmethyl bonds in preference to N-alkyl/aryl counterparts in N-arylmethylamines has been examined in detail and culminated in the design and development of new reactions, viz. novel approach to deprotection of N-benzylamines, reductive deoxygenation of carbonyls to methylenes and reductive amination of carbonyls under neutral conditions - all involving a known bonding change, viz. the directed cleavage of C-N bonds via LVT-mediated reactions.
- Talukdar, Sanjay,Banerji, Asoke
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p. 842 - 847
(2007/10/03)
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- Low-valent titanium mediated reductive deoxygenation of carbonyls to methylenes via carbon-nitrogen bond cleavage in N-(arylmethyl) anilines
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The reduction of aryl aldehydes and ketones in neutral medium, to the corresponding hydrocarbons via carbon-nitrogen bond cleavage of the intermediate N-(arylmethyl) anilines with low-valent titanium reagents is described. It provides a mild, convenient and selective pathway for deoxygenation of carbonyls without the production of any side product.
- Talukdar,Banerji
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p. 1051 - 1056
(2007/10/03)
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