- Copper(I)-catalyzed asymmetric hydrosilylations of imines at ambient temperatures
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Are you looking for an operationally simple means of preparing enantio-enriched benzylic-like centers bearing nitrogen? Consider this new and convenient alternative to asymmetric hydrogenation: CuH when ligated by an enantio-pure SEGPHOS ligand can cataly
- Lipshutz, Bruce H.,Shimizu, Hideo
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Read Online
- Microwave-accelerated enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines catalysed by β-aminoalcohols with the prolinol skeleton
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The addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines in the presence of a catalytic amount of a β-aminoalcohol with the prolinol framework under microwave irradiation gives the expected addition products in good yields and with an ee of u
- Almansa, Raquel,Guijarro, David,Yus, Miguel
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Read Online
- Asymmetric reduction method of nitrogen-phosphonyl protected imine
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The invention discloses an asymmetric reduction method of nitrogen phosphonyl protective imine. The nitrogen phosphonyl protective imine is reduced into chiral amine in a hydrogen atmosphere under theaction of a metal catalyst and alkali, and the metal catalyst is prepared from a metal iridium complex and a nitrogen-phosphorus chiral ligand. The method provided by the invention has the characteristics of high enantioselectivity, high yield and high conversion number (TON). The method can be used for synthesizing various substituted chiral amines, can be used as an important intermediate for preparing various medicines, and has important significance for industrial production of medicines.
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Paragraph 0073-0078
(2021/01/15)
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- Asymmetric Stepwise Reductive Amination of Sulfonamides, Sulfamates, and a Phosphinamide by Nickel Catalysis
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Asymmetric reductive amination of poorly nucleophilic sulfonamides was realized in the presence of nickel catalysts and titanium alkoxide. A wide range of ketones, including enolizable ketones and some biaryl ones, were converted into sulfonamides in excellent enantiomeric excess. The cyclization of sulfamates and intermolecular reductive amination of a diarylphosphinamide were also successful. Formic acid was used as a safe and economic surrogate of high-pressure hydrogen gas.
- Zhao, Xiaohu,Xu, Haiyan,Huang, Xiaolei,Zhou, Jianrong Steve
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supporting information
p. 292 - 296
(2018/12/13)
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- Asymmetric Transfer Hydrogenation in Thermomorphic Microemulsions Based on Ionic Liquids
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A thermomorphic ionic-liquid-based microemulsion system was successfully applied for the Ru-catalyzed asymmetric transfer hydrogenation of ketones. On the basis of the temperature-dependent multiphase behavior of the targeted microemulsion, simple product separation as well as catalyst recycling could be realized. The use of water-soluble ligands improved the immobilization of the catalyst in the microemulsion phase and significantly decreased the catalyst leaching into the organic layer upon extraction of the product. Eventually, the optimized microemulsion system could be applied to a wide range of aromatic ketones that were reduced with good isolated yields (up to 98%) and enantioselectivities (up to 97%), while aliphatic ketones were less successful.
- Hejazifar, Mahtab,Pálv?lgyi, ádám Márk,Bitai, Jacqueline,Lanaridi, Olga,Bica-Schr?der, Katharina
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p. 1841 - 1851
(2019/10/11)
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- A New Phosphine-Amine-Oxazoline Ligand for Ru-Catalyzed Asymmetric Hydrogenation of N-Phosphinylimines
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A series of chiral phosphine-amine-oxazoline (PAO) ligands with an NH moiety were synthesized and applied to the ruthenium-catalyzed asymmetric hydrogenation of N-phosphinylimines. The ligand bearing phenyl groups at the phosphorus moiety and isopropyl at the oxazoline moiety exhibits good activity and excellent enantioselectivity (up to 99% ee). This catalytic system provides an efficient and mild approach to access enantioriched amines.
- Ma, Xiaochen,Qiao, Lin,Liu, Guixia,Huang, Zheng
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supporting information
p. 1151 - 1155
(2018/10/15)
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- Iron(II)/(NH)2P2 Macrocycles: Modular, Highly Enantioselective Transfer Hydrogenation Catalysts
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A generalized protocol for the synthesis of chiral (NH)2P2 macrocycles allows changing the linker between the phosphines and gives access to a family of such ligands, as demonstrated for the propane-1,3-diyl analogue. The corresponding complexes based on earth-abundant and nontoxic iron were applied as catalysts in the asymmetric transfer hydrogenation of polar double bonds. Thanks to the ligand modularity and to the use of tunable isonitriles as ancillary ligands, the catalyst system can be individually optimized for each substrate to give high enantioselectivity (up to 99.9% conversion and 99.6% ee, TOF up to >3950 h-1) for a broad scope of 26 substrates.
- Bigler, Raphael,Huber, Raffael,St?ckli, Marco,Mezzetti, Antonio
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p. 6455 - 6464
(2016/10/18)
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- Enantioselective Hydrosilylation of Imines Catalyzed by Chiral Zinc Acetate Complexes
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A series of zinc acetate complexes with optically pure diphenylethanediamine (DPEDA)-derived ligands have been employed as enantioselective catalyst for the hydrosilylation of various imines. High control of stereoselectivity (up to 97% ee) and excellent yields (up to 96%) were gained for a broad range of N-phosphinoylimines by using (R,R)-N,N′-dibenzyl-1,2-diphenylethane-1,2-diamine. This is the first successful application of an air-stable and environmentally friendly chiral Zn(OAc)2 complex instead of the previously used harmful diethylzinc in the asymmetric reduction of the C=N double bond.
- Bez?ada, Agata,Szewczyk, Marcin,Mlynarski, Jacek
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p. 336 - 342
(2016/01/15)
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- Highly Enantioselective Transfer Hydrogenation of Polar Double Bonds by Macrocyclic Iron(II)/(NH)2P2 Catalysts
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We describe herein a new protocol for the synthesis of 2,2′-((1S,1′S)-ethane-1,2-diylbis(phenylphosphanediyl))dibenzaldehyde ((SP,SP)-5), which is the key intermediate in the synthesis of macrocyclic iron(II)/(NH)2P2 catalysts for the highly enantioselective transfer hydrogenation of polar double bonds. The dialdehyde (SP,SP)-5 was obtained as a single diastereoisomer and enantiomer from an optically pure H-phosphinate in 33% yield over five steps. It was further converted to afford multigram quantities of the macrocyclic iron(II)/(NH)2P2 complexes, which were tested in the asymmetric transfer hydrogenation of aryl alkyl ketones and imines in 2-propanol on a 100 mmol scale. Ten substrates, including challenging ones such as tert-butyl phenyl ketone and industrially relevant molecules such as 3,5-bis(trifluoromethyl)acetophenone, were reduced in high yield (89.0-99.7%), excellent enantioselectivity (95.8-99.4% ee), and with low catalyst loadings (S/C up to 10 000/1).
- Bigler, Raphael,Mezzetti, Antonio
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supporting information
p. 253 - 261
(2016/03/04)
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- Enantioselective addition of dialkylzinc to aromatic aldimines mediated by camphor-derived chiral β-amino alcohols
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The enantioselective addition of diethylzinc or dimethylzinc to N-(diphenylphosphinoyl)imines mediated by 1 or 2 could be achieved in high yields (70-97%) and enantioselectivities (85-98% ee). The catalytic loading of 1 or 2a could be reduced to 10 mol% f
- Huang, Wei-Ming,Uang, Biing-Jiun
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supporting information
p. 998 - 1003
(2015/03/31)
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- Synthesis of P-stereogenic compounds based on the diastereoselective ortho-lithiation of phosphinimidic amides
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The extension of the diastereoselective functionalization of the Ph2P group of C-chiral P,P-diphenyl phosphinimidic amides via directed ortho-lithiation (DoLi)-electrophilic quench reactions as a method for the preparation of structurally diverse P-stereogenic compounds is described. Transformations at both the phosphorus-containing and the ortho-functional groups provide access to a large variety of P-stereogenic derivatives with excellent stereocontrol. These transformations include aza-Wittig reactions, N-alkylations, methanolysis, nucleophilic displacements with Grignard reagents, phosphine oxide reductions, azide to amine conversions, halogen/metal exchange, and Suzuki cross-coupling and condensation reactions. These transformations increase the diversity of functional groups at the ortho-disubstituted phenyl ring and enable the synthesis of enantiopure ortho-formyl- and ortho-stannyl-phosphinic amides that are difficult to prepare by other methods. The new products synthesized might be used as building blocks for the construction of high value added P-stereogenic compounds. This is illustrated by the synthesis of [1,5,2]diazaphosphinin-6(5H)-one 21, a phosphazenylphosphinate (SPN,RPO)-22 and the analogues of relevant bidentate and tridentate privileged structures such as PHOX-like 23 and the heteroatomic N,O,P-tridentate ligand 25.
- Casimiro, María,Guedes, Guilherme P.,Iglesias, María José,López Ortiz, Fernando
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- METHOD OF ENANTIOSELECTIVE ADDITION TO IMINES
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The present invention relates to a method of enantioselective addition to imines, including: reacting R2CH═NY with R3ZnR4 in the presence of a compound represented by the following formula (I), in which Y, R1, R
- -
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Paragraph 0133
(2015/07/15)
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- Highly enantioselective transfer hydrogenation of ketones with chiral (NH)2P2 Macrocyclic Iron(II) complexes
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Bis(isonitrile) iron(II) complexes bearing a C2-symmetric diamino (NH)2P2 macrocyclic ligand efficiently catalyze the hydrogenation of polar bonds of a broad scope of substrates (ketones, enones, and imines) in high yield (up to 99.5 %), excellent enantioselectivity (up to 99 % ee), and with low catalyst loading (generally 0.1 mol %). The catalyst can be easily tuned by modifying the substituents of the isonitrile ligand. Paying the iron price: Bis(isonitrile) iron(II) complexes with a C2-symmetric diamino (NH)2P2 macrocyclic ligand efficiently catalyze the hydrogenation of polar bonds of a broad scope of substrates (ketones, enones, imines) in high yield (up to 99.5 %), excellent enantioselectivity (up to 99 % ee), and with low catalyst loading (generally 0.1 mol %).
- Bigler, Raphael,Huber, Raffael,Mezzetti, Antonio
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supporting information
p. 5171 - 5174
(2015/04/27)
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- Amine(imine)diphosphine iron catalysts for asymmetric transfer hydrogenation of ketones and imines
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A rational approach is needed to design hydrogenation catalysts that make use of Earth-abundant elements to replace the rare elements such as ruthenium, rhodium, and palladium that are traditionally used. Here, we validate a prior mechanistic hypothesis that partially saturated amine(imine)diphosphine ligands (P-NH-N-P) activate iron to catalyze the asymmetric reduction of the polar bonds of ketones and imines to valuable enantiopure alcohols and amines, with isopropanol as the hydrogen donor, at turnover frequencies as high as 200 per second at 28°C. We present a direct synthetic approach to enantiopure ligands of this type that takes advantage of the iron(lI) ion as a template. The catalytic mechanism is elucidated by the spectroscopic detection of iron hydride and amide intermediates.
- Zuo, Weiwei,Lough, Alan J.,Li, Young Feng,Morris, Robert H.
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p. 1080 - 1083
(2014/01/06)
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- Asymmetric transfer hydrogenation of ketimines using well-defined iron(II)-based precatalysts containing a PNNP ligand
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Well-defined iron(II)-based complexes containing PNNP ligands catalyze a highly enantioselective reduction of N-(diphenylphosphinoyl)- and N-(p-tolylsulphonyl)-ketimines. Under mild conditions and low catalyst loading, the ketimines are successfully reduced to the corresponding amines in enantiomeric excess ranging from 94 to 99%.
- Mikhailine, Alexandre A.,Maishan, Mazharul I.,Morris, Robert H.
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supporting information
p. 4638 - 4641
(2012/10/29)
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- METHOD OF ENANTIOSELECTIVE ADDITION TO IMINES
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The present invention relates to a method of enantioselective addition to imines, including: reacting R3CH═NY with R4ZnR5 in the presence of a compound represented by the following formula (I), in which Y, R1, R
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Page/Page column 13-14
(2012/01/14)
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- Application of rapidly generated bidentate ligand libraries to zinc catalyzed reductions
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A methodology for the combinatorial synthesis of bidentate ligands - allowing direct screening of reaction products without the need for isolation or purification - has been employed in a zinc catalyzed hydrosilylation. This reaction allowed the robustness of the methodology to be examined, by employing it in a challenging case where the metal complex is not pre-formed prior to catalysis. Four different ligand families have been examined: imines, aminals, bis-imines and oxazolines and related compounds, with a small library of each type produced and directly screened in the reaction. Three ligands providing enantioselectivities of 50% or more in this very challenging reaction were identified, and ees and conversions were equivalent whether the ligand was obtained as a crude mixture from a library synthesis or as an isolated, purified compound.
- Zaman, Tariq,Frauenlob, Robin,McCarthy, Robert,Walsh, Carolyn M.,Bergin, Enda
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p. 159 - 166
(2012/11/13)
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- Convenient, enantioselective hydrosilylation of imines in protic media catalyzed by a Zn-trianglamine complex
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Chiral hexamine macrocycle derived from trans-1,2-diaminocyclohexane (DACH) in a complex with diethylzinc efficiently catalyzes the asymmetric hydrosilylation of N-phosphorylated aryl-alkyl or aryl-aryl ketimines in protic media with enantiomeric excess o
- Gajewy, Jadwiga,Gawronski, Jacek,Kwit, Marcin
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scheme or table
p. 3863 - 3870
(2011/06/23)
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- Enantioselective synthesis of amines: General, efficient iron-catalyzed asymmetric transfer hydrogenation of imines
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In the iron age: A readily accessible, active iron catalyst serves in the straightforward, catalytic transfer hydrogenation of imines (see scheme). A series of imines are converted into chiral amines in high yields and very good enantioselectivities. This
- Zhou, Shaolin,Fleischer, Steffen,Junge, Kathrin,Das, Shoubhik,Addis, Daniele,Beller, Matthias
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experimental part
p. 8121 - 8125
(2011/02/22)
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- Asymmetric hydrogenation of cyclic N-sulfonylimines with phosphine-free chiral cationic Ru-MsDPEN catalysts
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Phosphine-free chiral cationic Ru/diamine complexes are effective catalysts for the asymmetric hydrogenation of a range of cyclic N-sulfonylimines, affording chiral sultam derivatives with good to excellent enantioselectivity (up to 94% ee).
- Chen, Fei,Li, Zhiwei,He, Yanmei,Fan, Qinghua
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body text
p. 1529 - 1532
(2011/07/07)
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- Reaction prospecting by 31P NMR: enantioselective rhodium-DuPhos catalysed addition of ZnMe2 to diphenylphosphinoylimines
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Chiral shift 31P NMR spectroscopy allows the identification of ligand leads in asymmetric catalyst systems for ZnMe2 addition to ArCH{double bond, long}NP(O)Ph2. Subsequent GC-based optimisation shows [RhCl(CH2{double bond, long}CH2)2]2 and (R,R)-MeDuPhos to be the optimal pre-catalyst combination (product in 78-93% ee). Transmetallation of [(MeDuPhos)Rh{N(P(O)Ph2-CHMeAr}] with ZnMe2 appears to be the rate limiting step of the catalytic cycle as competing coordination by the imine starting material leads to Ph2P(O)NHCH2Ar via MVP hydrogen-transfer. This limitation can largely be overcome by the slow addition of the imine.
- Crampton, Rosemary H.,Hajjaji, Samir El,Fox, Martin E.,Woodward, Simon
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body text
p. 2497 - 2503
(2010/04/05)
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- Highly enantioselective Pd-catalyzed asymmetric hydrogenation of activated imines
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(Chemical Equation Presented) Pd/bisphosphines complexes are highly effective catalysts for asymmetric hydrogenation of activated imines in trifluoroethanol. The asymmetric hydrogenation of N-diphenylphosphinyl ketimines 3 with Pd(CF3CO2)/(S)-SegPhos indicated 87-99% ee, and N-tosylimines 5 could gave 88-97% ee with Pd-(CF3CO 2)/(S)-SynPhos as a catalyst. Cyclic N-sulfonylimines 7 and 11 were hydrogenated to afford the useful chiral sultam derivatives in 79-93% ee, which are important organic synthetic intermediates and structural units of agricultural and pharmaceutical agents.
- Wang, You-Qing,Lu, Sheng-Mei,Zhou, Yong-Gui
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p. 3729 - 3734
(2008/02/04)
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- N-Benzyl-l-prolinol: an efficient catalyst for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines
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Commercially available N-benzyl-l-prolinol has shown to be a very efficient catalyst for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines. The use of 0.5 equiv of this β-aminoalcohol as a catalyst leads to the expecte
- Almansa, Raquel,Guijarro, David,Yus, Miguel
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p. 896 - 899
(2008/02/08)
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- Enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines catalyzed by β-aminoalcohols with the prolinol skeleton
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Several β-aminoalcohols with the prolinol framework are shown to be very efficient catalysts for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl)imines. The use of 0.5 equiv of the catalyst leads to the expected addition products in good yields and with ee up to 94% in a reaction time of only 4 h at room temperature. This ee is the highest value reported so far using 0.5 equiv of an aminoalcohol as a promoter. High enantioselectivities are obtained in the addition of dialkylzincs to both aromatic and aliphatic imines. The amount of the catalyst can be reduced to 0.25 equiv with a slight decrease in the ee. A very interesting effect of the addition rate and temperature on the enantioselectivity was also observed.
- Almansa, Raquel,Guijarro, David,Yus, Miguel
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p. 2828 - 2840
(2008/03/28)
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- Enantioselective MSPV reduction of ketimines using 2-propanol and (BINOL)AlIII
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A highly enantioselective Meerwein-Schmidt-Ponndorf-Verley (MSPV) reduction of N-phosphinoyl ketimines by (BINOL)AlIII/2-propanol is reported. Yields ranging between 79 and 85% with high enantiomeric excesses (93-98%) are observed for a wide ra
- Graves, Christopher R.,Scheidt, Karl A.,Nguyen, SonBinh T.
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p. 1229 - 1232
(2007/10/03)
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- Highly enantioselective Pd-catalyzed asymmetric hydrogenation of N-diphenylphosphinyl ketimines
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A variety of substituted N-diphenylphosphinyl imines were hydrogenated using Pd(CF3CO2)2/(S)-SEGPHOS as a catalyst with high enantioselectivities (86.7%-98.6% ee). Georg Thieme Verlag Stuttgart.
- Wang, You-Qing,Zhou, Yong-Gui
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p. 1189 - 1192
(2007/10/03)
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- Enantioselective reduction of imines catalyzed by a rhenium(V)-oxo complex
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An air- and moisture-tolerant enantioselective hydrosilylation of N-phosphinyl imines employing a chiral Re(V)-oxo complex as a catalyst is described. The chiral catalyst is a cyanobis(oxazoline) (CNbox)-ligated rhenium-oxo complex of the general formula
- Nolin, Kristine A.,Ahn, Richard W.,Toste, F. Dean
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p. 12462 - 12463
(2007/10/03)
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- Unprecedented asymmetric induction through configurationally stable lithium N-(α-methylbenzyl)phosphinamides. A new entry to enantiomerically pure γ-aminophosphinic acids and esters
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The first examples of configurationally stable N-benzyl-N-phosphinoyl carbanions are described. Their applications to the synthesis of homochiral γ-aminophosphinic acids and esters via highly enantioselective dearomatising reactions are shown. The Royal S
- Fernandez, Ignacio,Ruiz Gomez, Gloria,Alfonso, Ignacio,Iglesias, Maria J.,Lopez Ortiz, Fernando
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p. 5408 - 5410
(2007/10/03)
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- Application of monodentate secondary phosphine oxides, a new class of chiral ligands, in Ir(I)-catalyzed asymmetric imine hydrogenation
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(Matrix presented) Secondary phosphine oxides were prepared from R 1PCl2 and R2MgBr, followed by hydrolysis. They were obtained in an enantiopure form by preparative chiral HPLC. These new monodentate ligands were tested in the iridium-catalyzed hydrogenation of imines at 25 bar. Enantioselectivities up to 76% were obtained at L/lr = 2. Addition of pyridine (Pyr/lr = 1:2) raised the ee to 83%. Using pyridine as an additive allowed reduction of the L/lr ratio to 1 without reduction of ee.
- Jiang, Xiao-Bin,Minnaard, Adriaan J.,Hessen, Bart,Feringa, Ben L.,Duchateau, Alexander L. L.,Andrien, Jean G. O.,Boogers, Jeroen A. F.,De Vries, Johannes G.
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p. 1503 - 1506
(2007/10/03)
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- Enantioselective reduction of C=O and C=N bonds by TADDOL-containing aluminum hydride reagents based on NaAlH4 and AlH3
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Prochiral substrates (alkyl aryl ketones, cyclopropyl methyl ketone, 1-indanone, 1-tetralone, ethyl 2-oxo-4-phenylbutyrate, and N- (diphenylphosphinyl)acetophenoneimine) were subjected to asymmetric reduction with aluminum hydride reagents, which were prepared by modifications of NaAlH4 or AlH3 with chiral α,α,α′, α′-tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL). The effects of the nature of the substituents in TADDOL, the structure of the prochiral substrate, and the reaction conditions on the stereochemistry of reduction were investigated. The highest enantioselectivity (70-90% ee) was achieved upon reduction of alkyl aryl ketones and N-(diphenylphosphinyl)acetophenoneimine with NaAl(TADDOLate)H2 in THF or diglyme at a temperature from -70 to -20°C. The mechanism of asymmetric induction in the reduction reactions of ketones with aluminum hydride reagents is discussed. The stereochemical results of reduction were explained by comparing three-dimensional models of the most probable transition states.
- Vinogradov,Gorshkova,Chel'tsova,Pavlov,Razmanov,Ferapontov,Malyshev,Heise
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p. 471 - 479
(2007/10/03)
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- Enantioselective borohydride reduction catalyzed by optically active cobalt complexes
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The highly enantioselective borohydride reduction of aromatic ketones or imines to the corresponding alcohols was developed in the presence of a catalytic amount of an optically active cobalt(II) complex catalyst. This enantioselective reduction is carried out using a precisely premodified borohydride with alcohols such as tetrahydrofurfuryl alcohol, ethanol and methanol. High optical yields are obtained by choosing the appropriate alcohol as modifiers and a suitable β-ketoiminato ligand of the catalyst. The enantioselective borohydride reduction has been successfully applied to the preparation of optically active 1,3-diols, the stereoselective reduction of diacylferrocenes, and dynamic and/or kinetic resolution of 1,3-dicarbonyl compounds.
- Yamada, Tohru,Nagata, Takushi,Sugi, Kiyoaki D.,Yorozu, Kiyotaka,Ikeno, Taketo,Ohtsuka, Yuhki,Miyazaki, Daichi,Mukaiyama, Teruaki
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p. 4485 - 4509
(2007/10/03)
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- Catalytic enantioselective addition of dialkylzinc to N-diphenylphosphinoylimines. A practical synthesis of α-chiral amines
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The enantioselective addition of dialkylzinc reagents to N-diphenylphosphinoylimines derived from aryl-, furyl-, and cyclopropylaldehydes is efficiently catalyzed by a copper(II) triflate/(R,R)-MeDUPHOS complex. The yields are high (51-98%), and the enant
- Boezio, Alessandro A.,Charette, Andre B.
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p. 1692 - 1693
(2007/10/03)
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- Chiral phosphinamides: New catalysts for the asymmetric reduction of ketones by borane
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We have identified a new class of catalysts for the asymmetric reduction of prochiral ketones by borane. Key to the architecture of effective catalysts is an N-P=O structural unit which may be part of a phosphinamide, phosphonamide or a related structure.
- Burns, Barry,King, N. Paul,Tye, Heather,Studley, John R.,Gamble, Mark,Wills, Martin
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p. 1027 - 1038
(2007/10/03)
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- Enantioselective Addition of Dialkylzinc Reagents to N-(Diphenylphosphinoyl) Imines Promoted by 2-Azanorbornylmethanols
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A set of new β-amino alcohols 2, with the 2-azanorbornyl framework, has been prepared and evaluated as promoters for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl) imines 1. By variation of the substitution pattern in the ligand, ee's up to 92% could be obtained. Although a stoichiometric amount of the ligand was used, about 90% of it could be recovered during the workup. Amino alcohol 2b, that gave the best enantioselectivities in the stoichiometric reaction, was also applied in a catalytic process, and ee's up to 85% were achieved using 0.25 equiv of the ligand, which is the highest ee obtained so far using that catalytic amount of the ligand. Addition products 3 could be converted into the free amines 4 without racemization by acidic hydrolysis. The utility of ligands 2 as catalysts in the addition of diethylzinc to benzaldehyde has also been investigated, and ee's up to 75% were achieved.
- Guijarro, David,Pinho, Pedro,Andersson, Pher G.
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p. 2530 - 2535
(2007/10/03)
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- Enantioselective borohydride reduction of N-diphenylphosphinyl imines using optically active cobalt(II) complex catalysts
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The enantioselective borohydride reduction using optically active cobalt(II) complex catalysts was successfully applied to various aryl N-diphenylphosphinyl imines, and the corresponding reduced products were obtained in good yields with high enantiomeric excesses (up to 99% ee). The optically active primary amines were obtained by the successive hydrolysis under mild conditions.
- Sugi, Kiyoaki D.,Nagata, Takushi,Yamada, Tohru,Mukaiyama, Teruaki
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p. 493 - 494
(2007/10/03)
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- Enantioselective addition of dialkylzincs to N-diphenylphosphinylimines using polymer-supported N,N-dialkylnorephedrines as chiral ligands
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Chiral N,N-dialkylnorephedrines supported on polystyrene resin catalyse the enantioselective addition of dialkylzincs to N-diphenylphosphinylimine, affording optically active N-diphenylphosphinylamines with high enantiomeric excess. The influence on the e
- Suzuki, Takefumi,Shibata, Takanori,Soai, Kenso
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p. 2757 - 2760
(2007/10/03)
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- Preparation and Use of Aziridino Alcohols as Promoters for the Enantioselective Addition of Dialkylzinc Reagents to N-(Diphenylphosphinoyl) Imines
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A set of chiral aziridino alcohols 2-5 has been synthesized starting from either readily available amino acids (L-serine, L-threonine, and allo-L-threonine) or simple olefins (using Sharpless asymmetric aminohydroxylation and dihydroxylation reactions). Chiral ligands 2-5 have been tested as promoters for the enantioselective addition of dialkylzinc reagents to N-(diphenylphosphinoyl) imines 1. The influence of the substituants on the aziridine ring and the alcohol moiety on the selectivity has been studied, and in the best case, an enantiomeric excess of up to 94% could be obtained. Acidic hydrolysis of the initially formed N-protected amines 6 led to the corresponding free amines 7 without racemization. Although a stoichiometric amount of the ligand was used, about 90% of it could be recovered during the workup and reused without significant loss of chiral induction. The utility of the aziridino alcohols 2-5 as catalysts for the same reaction has also been evaluated and enantiomeric excesses of up to 76% were achieved using 0.25 equiv of the chiral ligand. A possible transition state for the addition reaction is also proposed.
- Andersson, Pher G.,Guijarro, David,Tanner, David
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p. 7364 - 7375
(2007/10/03)
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- New catalysts containing an N-P=O structural unit for the asymmetric reduction of ketones
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New catalysts for the asymmetric reduction of ketones to chiral alcohols are described. Together they represent an entirely novel class of catalysts which have in common an N-P=O structural unit.
- Burns,Studley,Wills
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p. 7105 - 7106
(2007/10/02)
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- Highly Enantioselective Alkylation of Carbon-Nitrogen Double Bonds. Catalytic and Stoichiometric Asymmetric Synthesis of Optically Active Amines by the Enantioselective Addition of Dialkylzinc Reagents to N-Diphenylphosphinoylimines
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The first highly enantioselective alkylation of carbon-nitrogen double bonds (of N-diphenylphosphinoylimines) with dialkylzinc reagents promoted by chiral amino alcohols afforded optically active phosphoramides (precursors of amines) in up to 91percent en
- Soai, Kenso,Hatanaka, Toshihiro,Miyazawa, Tohru
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p. 1097 - 1098
(2007/10/02)
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- Asymmetric Reduction of Phosphinyl Imines with Hydride Reagents. Enantioselective Synthesis of Chiral Primary Amines
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Prochiral diphenylphosphinyl imines are asymmetrically reduced by chiral hydride reagents to chiral diphenylphosphinylamines.For dialkyl examples, the enantioselectivities obtained are the highest thus far for hydride reductions of imine derivatives.
- Hutchins, Robert O.,Abdel-Magid, Ahmed,Stercho, Yuriy P.,Wambsgans, Anthony
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p. 702 - 704
(2007/10/02)
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