- Isolation of Racemic 2,4-Pentanediol and 2,5-Hexanediol from Commercial Mixtures of Racemic and Meso Isomers by way of Cyclic Sulfites
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Enantiomerically pure diols with C2 symmetry such as 2,3-butanediol, 1, 2,4-pentanediol, 2, and 2,5-hexanediol, 3, are useful chiral auxiliaries, but they are expensive because chemists lack good synthetic routes that eliminate both the meso isomer and one enantiomer.Enzymic resolutions efficiently separate the enantiomer, but do not remove the meso isomer.To simplify enzymic resolutions of 2 and 3, we developed simple methods to isolate the racemic isomer from commercial mixtures of racemic and meso isomers 1 or 2, the meso isomer selectivity reacted with SOCl2 to give a cyclic sulfite that was removed by column chromatography to leave (+/-)-2, 92percent de, 1.4 g, 55percent yield.For 3, both meso and racemic isomers reacted with SOCl2 to give cyclic sulfites, but the sulfite derived from the meso isomer rearranged to trans-2,5-dimethyltetrahydrofuran under acidic conditions.Hydrolysis of the remaining sulfite gave (+/-)-3, 84percent de, 1.1 g, 37percent yield.Resolution of (+/-)-2 and (+/-)-3 using lipase from Pseudomonas cepacia yielded (2R,4R)-2-diacetate, 78 percent ee, >97percent de, 40percent of theory and (2R,5R)-3-diacetate, 94percent ee, >97percent de, 47percent of theory.Previously reported acetylations of 2 and 3 by lipase from Candida antarctica (CAL) or by lipase from Pseudomonas sp. (Amonolipase AK) are more enantioselective and thus, the best route to enantiomerically and diastereomerically pure 2 and 3 is removal of the meso isomer by way of cyclic sulfites followed by resolution with CAL or Amano lipase AK.
- Caron, Gaetan,Kazlauskas, Romas J.
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Read Online
- Synthesis and Applications of (Pyridyl)imine Fe(II) Complexes as Catalysts in Transfer Hydrogenation of Ketones
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Abstract: Chiral (pyridyl)imine Fe(II) complexes, [Fe(L1)3]2+[PF6?]2, (Fe1), [Fe(L2)3]2+[PF6?]2, (Fe2), [Fe(L3)3]2+[PF6?]2 (Fe3), and [Fe(L4)3]2+[PF6?]2 (Fe4) were synthesised by reactions of synthons (S-)-1-phenyl-N-(pyridine-2-yl) ethylidine)ethanamine (L1), (R-)-1-phenyl-N-(pyridine-2-yl) ethylidine) ethanamine (L2), (S)-1-phenyl-N-(pyridine-2-yl methylene) ethanamine (L3) and (S)-1-phenyl-N-(pyridine-2-yl methylene)ethanamine (L4) with the FeCl2 salt. The solid-state structure of complex Fe4 showed that the?Fe atom contains three units of bidentate bound ligand L4 to form a six-coordinate cationic compound. The Fe(II) complexes were evaluated as catalysts in asymmetric transfer hydrogenation of ketones reactions and showed moderate catalytic activities with low enantioselectivity. Catalytic activities of the respective complexes were regulated by the nature of the metal complexes, ketone substrate and reaction conditions. Mercury and sub-stoichiometric poisoning experiments implicate possible formation of both active Fe(0) nanoparticles and Fe(II) homogeneous intermediates. Graphic Abstract: [Figure not available: see fulltext.]
- Kumah, Robert T.,Vijayan, Paranthaman,Ojwach, Stephen O.
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p. 344 - 352
(2020/07/25)
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- Vinylidene Homologation of Boronic Esters and its Application to the Synthesis of the Proposed Structure of Machillene
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Alkenyl boronic esters are important reagents in organic synthesis. Herein, we report that these valuable products can be accessed by the homologation of boronic esters with lithiated epoxysilanes. Aliphatic and electron-rich aromatic boronic esters provided vinylidene boronic esters in moderate to high yields, while electron-deficient aromatic and vinyl boronic esters were found to give the corresponding vinyl silane products. Through DFT calculations, this divergence in mechanistic pathway has been rationalized by considering the stabilization of negative charge in the C?Si and C?B bond breaking transition states. This vinylidene homologation was used in a short six-step stereoselective synthesis of the proposed structure of machillene, however, synthetic and reported data were found to be inconsistent.
- Fordham, James M.,Grayson, Matthew N.,Aggarwal, Varinder K.
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supporting information
p. 15268 - 15272
(2019/10/21)
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- Total Synthesis of (?)-Histrionicotoxin through a Stereoselective Radical Translocation–Cyclization Reaction
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Stereoselective total syntheses of (?)-histrionicotoxin and (?)-histrionicotoxin 235A are described. The 1-azaspiro[5.5]undecane skeleton was constructed diastereoselectively by a radical translocation–cyclization reaction involving a chiral cyclic acetal; the use of tris(trimethylsilyl)silane was crucial for the high diastereoselectivity. The cyclization product was converted into (?)-histrionicotoxin 235A through a one-pot partial-reduction–allylation reaction of a derivative containing an unprotected lactam. Finally, two terminal alkenes were transformed into enynes with the 1,3-amino alcohol protected as an oxathiazolidine oxide to complete the total synthesis of (?)-histrionicotoxin.
- Sato, Manabu,Azuma, Hiroki,Daigaku, Akihiro,Sato, Sota,Takasu, Kiyosei,Okano, Kentaro,Tokuyama, Hidetoshi
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supporting information
p. 1087 - 1091
(2017/01/18)
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- WATER-INSOLUBLE RUTHENIUM CATALYST COMPOSITION FOR USE IN AQUEOUS HYDROGENATION REACTIONS
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The invention relates to a method for converting a precatalyst complex to an active catalyst complex, wherein the precatalyst complex and the active catalyst complex comprise a ruthenium atom and an optically active ligand that is insoluble in water, and the active catalyst complex furthermore comprises a monohydride and a water molecule. The method comprises the steps of providing water as an activation solvent system with a pH value equal or below 2, and solving said precatalyst complex, an acid, and hydrogen therein. The invention further relates to a method for manufacturing a catalyst composition, a method for hydrogenating a substrate molecule and a reaction mixture.
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- Method for preparing beta-diol from beta-diketone
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The invention relates to a method for preparing beta-diol from beta-diketone. The method is characterized in that beta-diketone contacts and reacts with hydrogen in the presence of a hydrogenation catalyst under fixed bed reaction conditions, the hydrogenation catalyst comprises an active component copper and a carrier, and the hydrogenation catalyst preferably comprises an assistant component selected from VIIIB and IB group elements, the assistant is preferably selected from one or more of Ni, Co and Ag, and the carrier is SiO2. The method adopting a fixed bed hydrogenation technology and using a copper-containing supported catalyst has the advantages of no pollution to environment, mild operating conditions, and suitableness for continuous production.
- -
-
Paragraph 0037; 0048; 0049
(2016/11/24)
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- Method for preparing beta-diol from beta-diketone by hydrogenation
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The invention relates to a method for preparing beta-diol from beta-diketone by hydrogenation. The method comprises the following steps: in the presence of a catalyst and under the fixed-bed hydrotreating reaction condition, enabling beta-diketone to be in contact with hydrogen, so as to obtain beta-diol, wherein the catalyst contains CuO and ZnO, preferably also contains Al2O3, and more preferably also contains alkali metal oxides. According to the method for preparing beta-diol from beta-diketone by hydrogenation, provided by the invention, the technology of continuously producing beta-diol by adopting a fixed bed device is realized, the technology is simple and convenient to operate, the utilization ratio of raw materials and the production efficiency of products are improved, the reaction does not need to be carried out under high pressure, and potential safety hazards are reduced.
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Paragraph 0041-0044
(2017/02/23)
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- A β-diketone fixed bed hydrogenation method for preparing β-diol (by machine translation)
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The invention relates to a β-diketone fixed bed hydrogenation method for preparing β-diol, including in the presence of hydrogenation catalyst under conditions and fixed bed reaction of the β-diketone reaction contact with hydrogen gas; the hydrogenation catalyst comprises active component copper and carrier, wherein in order to weight part, the content of copper is 20-35 parts, carrier is in a content of 60-80 parts. Preferably, the hydrogenation catalyst also includes selected from group IB and VIIIB additive component, more preferably the assistant is selected from Ni, Ag Co and in one or several of, the carrier is SiO 2. The method provided by the present invention which adopts a fixed bed hydrogenation process and the use of copper-containing supported catalyst, no pollution to the environment, mild operating conditions, is suitable for continuous production. (by machine translation)
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Paragraph 0038-0039
(2017/02/28)
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- Method for preparation of beta-diol
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The present invention relates to a method for preparation of a beta-diol from a beta-diketone by hydrogenation, the method comprises contact reaction of the beta-diketone and hydrogen in the presence of a hydrogenation catalyst and under fixed bed reaction conditions, the hydrogenation catalyst is a non-noble metal catalyst, includes a metal component and a carrier, and can be prepared by a conventional method. The method uses a fixed bed hydrogenation process, and is free of environmental pollution, mild in operating conditions, and suitable for continuous production.
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Paragraph 0030-0031
(2017/03/17)
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- Walphos versus biferrocene-based walphos analogues in the asymmetric hydrogenation of alkenes and ketones
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Two representative Walphos analogues with an achiral 2,2″- biferrocenediyl backbone were synthesized. These diphosphine ligands were tested in the rhodium-catalyzed asymmetric hydrogenation of several alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The results were compared with those previously obtained on using biferrocene ligands with a C 2-symmetric 2,2″-biferrocenediyl backbone as well as with those obtained with Walphos ligands. The application of one newly synthesized ligand in the hydrogenation of 2-methylcinnamic acid gave (R)-2-methyl-3- phenylpropanoic acid with full conversion and with 92% ee. The same ligand was used to transform 2,4-pentanedione quantitatively and diastereoselectively into (S,S)-2,4-pentanediol with 98% ee.
- Zirakzadeh, Afrooz,Gross, Manuela A.,Wang, Yaping,Mereiter, Kurt,Weissensteiner, Walter
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p. 1945 - 1952
(2014/05/20)
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- Water-insoluble Ruthenium catalyst composition for use in aqueous hydrogenation reactions
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The invention relates to a method for converting a precatalyst complex to an active catalyst complex, wherein the precatalyst complex and the active catalyst complex comprise a ruthenium atom and an optically active ligand that is insoluble in water, and the active catalyst complex furthermore comprises a monohydride and a water molecule. The method comprises the steps of providing water as an activation solvent system with a pH value equal or below 2, and solving said precatalyst complex, an acid, and hydrogen therein. The invention further relates to a method for manufacturing a catalyst composition, a method for hydrogenating a substrate molecule and a reaction mixture.
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- Biferrocene-based diphosphine ligands: Synthesis and application of walphos analogues in asymmetric hydrogenations
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A total of four biferrocene-based Walphos-type ligands have been synthesized, structurally characterized, and tested in the rhodium-, ruthenium- and iridium-catalyzed hydrogenation of alkenes and ketones. Negishi coupling conditions allowed the biferrocene backbone of these diphosphine ligands to be built up diastereoselectively from the two nonidentical and nonracemic ferrocene fragments (R)-1-(N,N-dimethylamino)ethylferrocene and (SFc)-2- bromoiodoferrocene. The molecular structures of (SFc)-2- bromoiodoferrocene, the coupling product, two ligands, and the two complexes ([PdCl2(L)] and [RuCl(p-cymene)(L)]PF6) were determined by X-ray diffraction. The structural features of complexes and the catalysis results obtained with the newly synthesized biferrocene-based ligands were compared with those of the corresponding Walphos ligands.
- Zirakzadeh, Afrooz,Gross, Manuela A.,Wang, Yaping,Mereiter, Kurt,Spindler, Felix,Weissensteiner, Walter
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supporting information
p. 1075 - 1084
(2013/04/23)
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- Rabbit 3-hydroxyhexobarbital dehydrogenase is a NADPH-preferring reductase with broad substrate specificity for ketosteroids, prostaglandin D2, and other endogenous and xenobiotic carbonyl compounds
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3-Hydroxyhexobarbital dehydrogenase (3HBD) catalyzes NAD(P) +-linked oxidation of 3-hydroxyhexobarbital into 3-oxohexobarbital. The enzyme has been thought to act as a dehydrogenase for xenobiotic alcohols and some hydroxysteroids, but its physiological function remains unknown. We have purified rabbit 3HBD, isolated its cDNA, and examined its specificity for coenzymes and substrates, reaction directionality and tissue distribution. 3HBD is a member (AKR1C29) of the aldo-keto reductase (AKR) superfamily, and exhibited high preference for NADP(H) over NAD(H) at a physiological pH of 7.4. In the NADPH-linked reduction, 3HBD showed broad substrate specificity for a variety of quinones, ketones and aldehydes, including 3-, 17- and 20-ketosteroids and prostaglandin D2, which were converted to 3α-, 17β- and 20α-hydroxysteroids and 9α,11β- prostaglandin F2, respectively. Especially, α-diketones (such as isatin and diacetyl) and lipid peroxidation-derived aldehydes (such as 4-oxo- and 4-hydroxy-2-nonenals) were excellent substrates showing low Km values (0.1-5.9 μM). In 3HBD-overexpressed cells, 3-oxohexobarbital and 5β-androstan-3α-ol-17-one were metabolized into 3-hydroxyhexobarbital and 5β-androstane-3α,17β-diol, respectively, but the reverse reactions did not proceed. The overexpression of the enzyme in the cells decreased the cytotoxicity of 4-oxo-2-nonenal. The mRNA for 3HBD was ubiquitously expressed in rabbit tissues. The results suggest that 3HBD is an NADPH-preferring reductase, and plays roles in the metabolisms of steroids, prostaglandin D2, carbohydrates and xenobiotics, as well as a defense system, protecting against reactive carbonyl compounds.
- Endo, Satoshi,Matsunaga, Toshiyuki,Matsumoto, Atsuko,Arai, Yuki,Ohno, Satoshi,El-Kabbani, Ossama,Tajima, Kazuo,Bunai, Yasuo,Yamano, Shigeru,Hara, Akira,Kitade, Yukio
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p. 1366 - 1375
(2013/11/19)
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- An efficient one-step chemoselective reduction of alkyl ketones over aryl ketones in β-diketones using LiHMDS and lithium aluminium hydride
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β-Hydroxy ketones were synthesized in one-pot from β-diketones by reducing alkyl ketones chemoselectively by keeping aryl ketone intact. Initially, β-diketones were enolized using LiHMDS and later alkyl ketone was chemoselectively reduced efficiently by lithium aluminium hydride. This method produces β- hydroxyl ketones from the corresponding β-diketones in high yield.
- Veeraswamy,Indrasena Reddy,Venkat Ragavan,Tirumal Reddy,Yennam, Satyanarayana,Jayashree
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experimental part
p. 4651 - 4653
(2012/09/05)
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- Albumin-directed stereoselective reduction of 1,3-diketones and β-hydroxyketones to anti diols
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The reduction of 1,3-diketones and β-hydroxyketones with NaBH 4 in aqueous acetonitrile is highly stereoselective in the presence of stoichiometric amounts of bovine or human albumin, giving anti 1,3-diols with d.e. up to 96%. The same reaction, without albumin, gives syn and anti 1,3-diols in approximately 1:1 ratio. The presence of an aromatic carbonyl group is essential for diastereoselectivity in the NaBH4/albumin reduction of both 1,3-diketones and β-hydroxyketones. Thus, 3-hydroxy-1-(p-tolyl)-1- butanone is stereoselectively reduced in the presence of albumin, while reduction of its isomer 4-(p-tolyl)-4-hydroxy-2-butanone is not stereoselective. The albumin-controlled reduction is not stereospecific as both enantiomers of 1-aryl-3-hydroxy-1-butanones are reduced to diols with identical stereoselectivities. Circular dichroism of the bound substrates confirms that aromatic ketones are recognized by the protein's IIA binding site. Binding studies also suggest that 1,3-diketones are recognized in their enol form. From the effect of pH on binding of a diketone it is concluded that, in the complex with the substrate, ionizable residues His242 and Lys199 are in the neutral and protonated forms, respectively. A homology model of BSA was obtained and docking of model substrates confirms the preference of the protein for aromatic ketones. Modelling of the complexes with the substrates also allows us to propose a mechanism for the reduction of 1,3-diketones in which the chemoselective reduction of the first (aliphatic) carbonyl is followed by the diastereoselective reduction of the second (aromatic) carbonyl. The role of albumin is thus a combination of chemo- and stereocontrol.
- Berti, Federico,Bincoletto, Simone,Donati, Ivan,Fontanive, Giampaolo,Fregonese, Massimo,Benedetti, Fabio
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experimental part
p. 1987 - 1999
(2011/04/25)
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- Heterogenized Ru(II) phenanthroline complex for chemoselective hydrogenation of diketones under biphasic aqueous medium
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The chemoselective hydrogenation of acetylacetone to 4-hydroxypentan-2-one over immobilized ruthenium phenanthroline metal complexes in amino functionalized MCM-41 in biphasic aqueous reaction medium was investigated. The catalyst was characterized by XRD, TEM, surface analysis, FT-IR and UV-vis to understand the morphology, complex geometry, and XPS such that the oxidation state of the metal complex inside the MCM-41 framework could be understood. The use of water as a solvent, not only gives high activity and selectivity for hydrogenation of acetylacetone, but also gives a path for an environmentally safer process. The optimizations of ligand, metal to ligand ratio, the choice of solvent and other reaction parameters were studied in detail. The heterogeneous catalytic system gave a higher degree of chemoselectivity (99%) towards 4-hydroxypentan-2-one as compared to homogeneous catalyst when hydrogenation was carried out using water as a solvent. The immobilized ruthenium-phenanthroline complex was easily separated and reused.
- Deshmukh, Amit,Kinage, Anil,Kumar, Rajiv,Meijboom, Reinout
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body text
p. 114 - 120
(2011/02/23)
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- Highly efficient and stereoselective biosynthesis of (2S,5S)-hexanediol with a dehydrogenase from Saccharomyces cerevisiae
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The enantiopure (2S,5S)-hexanediol serves as a versatile building block for the production of various fine chemicals and pharmaceuticals. For industrial and commercial scale, the diol is currently obtained through bakers' yeast-mediated reduction of 2,5-hexanedione. However, this process suffers from its insufficient space-time yield of about 4 g L-1 d-1 (2S,5S)-hexanediol. Thus, a new synthesis route is required that allows for higher volumetric productivity. For this reason, the enzyme which is responsible for 2,5-hexanedione reduction in bakers' yeast was identified after purification to homogeneity and subsequent MALDI-TOF mass spectroscopy analysis. As a result, the dehydrogenase Gre2p was shown to be responsible for the majority of the diketone reduction, by comparison to a Gre2p deletion strain lacking activity towards 2,5-hexanedione. Bioreduction using the recombinant enzyme afforded the (2S,5S)-hexanediol with >99% conversion yield and in >99.9% de and ee. Moreover, the diol was obtained with an unsurpassed high volumetric productivity of 70 g L-1 d-1 (2S,5S)-hexanediol. Michaelis-Menten kinetic studies have shown that Gre2p is capable of catalysing both the reduction of 2,5-hexanedione as well as the oxidation of (2S,5S)-hexanediol, but the catalytic efficiency of the reduction is three times higher. Furthermore, the enzyme's ability to reduce other keto-compounds, including further diketones, was studied, revealing that the application can be extended to α-diketones and aldehydes.
- Mueller, Marion,Katzberg, Michael,Bertau, Martin,Hummel, Werner
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experimental part
p. 1540 - 1550
(2010/07/04)
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- Synthesis, coordination behaviour, structural features and use in asymmetric hydrogenations of bifep-type biferrocenes
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A protocol for the synthesis of C2- and C1-symmetric 2,2″-diarylphosphino-substituted biferrocenes (bifep-type ligands) is presented and the preparation of four representatives is described [(S p,Sp)-2-R12P-2″- R 22P-1,1″-biferrocene; 1 (bifep): R1 = R2 = Ph; 2: R1 = Ph, R2 = Cy; 3: R1 = R2 = 3,5-Me2C6H3; 4: R1 = 3,5-Me2-4-OMe-C6H2, R2 = 3,5-(CF3)2C6H3]. In addition, the synthesis of three palladium(ii) complexes ([PdX2(L)], 10: L = 1, X = Cl; 11: L = 4, X = Cl; 12: L = 1, X = C6F5 and of four bifep ruthenium complexes (13: [RuCl(p-cymene)(1)]PF6; 14: [RuI(p-cymene)(1)]PF6; 15: [RuCl(benzene)(1)]PF6; 16: [RuI(p-cymene)(1)]I) is reported. In the solid state the biferrocene unit of complexes 10, 11 and 15 adopt either a (P)-shaped (10) or an (M)-shaped (11, 15) conformation. In solution, palladium complexes 10 and 11 are present as equilibrium mixtures of rapidly interconverting (P)- and (M)-shaped conformers. Rhodium- and iridium-mediated asymmetric hydrogenations of a number of olefins and one imine give products with only low to moderate enantiomeric excess, while in the ruthenium-catalyzed hydrogenation of ketones a maximum e.e. of 82% is obtained. The low enantioselectivities are assumed to be related to the conformational flexibility of bifep-type ligands.
- Espino, Gustavo,Xiao, Li,Puchberger, Michael,Mereiter, Kurt,Spindler, Felix,Manzano, Blanca R.,Jalon, Felix A.,Weissensteiner, Walter
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experimental part
p. 2751 - 2763
(2009/06/28)
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- PREPARATION OF DERIVATIVE OF POLYHYDRIC ALCOHOLS
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A method for converting a polyhydric alcohol into propylene glycol and butanediols is disclosed. Also disclosed are methods for converting polyhydric alcohols into three-carbon products and four-carbon products. Also disclosed are methods for maximizing conversion of polyhydric alcohols and minimizing formation of reaction products that are difficult to remove from the desired product. In other embodiments, methods are described to optimize use of reactants, including hydrogen, in hydrogenolysis of polyhydric alcohols.
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Page/Page column 18-19; 25
(2008/12/08)
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- Hydrogenolysis of Glycerol and Products Produced Therefrom
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Processes for the hydrogenolysis of glycerol, as well as products produced therefrom are disclosed.
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Page/Page column 6
(2008/06/13)
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- Chemoselective hydrolysis of terminal isopropylidene acetals in acetonitrile using molecular iodine as a mild and efficient catalyst
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A simple, mild and efficient method for deprotection of acetonides in the presence of molecular iodine is described. Acid labile protecting groups such as PMB, OMe, OBn, allyl and propargyl are compatible with the reaction conditions, while TBS, TBDPS, TMS and THP ethers were unstable under the same conditions.
- Yadav,Satyanarayana,Raghavendra,Balanarsaiah
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p. 8745 - 8748
(2007/10/03)
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- Facile deoxygenation of dicarbonyl compounds using a samarium diiodide-additive system
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The reduction of α- and β-dicarbonyl compounds was investigated with samarium diiodide in the presence of additive. Diketones and ketocarboxylic acids were easily reduced at room temperature to give the mono-alcohols in good to excellent yield, and ketoester afforded the saturated ester as the major product in moderate yield. These reductions containing the reductive deoxygenation can be rapidly performed under the facile and mild conditions by this method.
- Kamochi, Yasuko,Kudo, Tadahiro,Masuda, Toshinobu,Takadate, Akira
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p. 1017 - 1020
(2007/10/03)
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- AMINE-SUBSTITUTED DIPHENYLDIPHOSPHINES
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The invention relates to the 1,1'-diphenyl-2,2'-diphosphines of formulae (Ia), (Ib), having at least one amine substituent in para position to the phosphine group. These novel compounds are ligands for metal complexes that are catalysts for asymmetric addition reactions of prochiral organic compounds and whose catalytic properties can be adjusted in a substrate-specific manner via the substitution of the amino group.
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Page/Page column 60-61
(2008/06/13)
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- A Novel Class of Ferrocenyl-Aryl-Based Diphosphine Ligands for Rh- And Ru-Catalysed Enantioselective Hydrogenation
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A series of diphosphines of the novel Walphos ligand family all based on a phenylferrocenylethyl backbone were synthesised in a four-step sequence. In the rhodium- or ruthenium-catalysed asymmetric hydrogenation of olefins and ketones enantioselectivities of up to 95% and 97%, respectively, were obtained. A 2-isopropylcinnamic acid derivative of industrial interest was hydrogenated in 95% ee and with turnover numbers of > 5000.
- Sturm, Thomas,Weissensteiner, Walter,Spindler, Felix
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p. 160 - 164
(2007/10/03)
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- Synthesis of a new class of chiral 1,5-diphosphanylferrocene ligands and their use in enantioselective hydrogenation
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A new family of ferrocenylphosphane ligands has been prepared. Their flexible synthesis allows many structural modifications. The asymmetric induction of these ligands was examined in the hydrogenation of functionalized C=C, C=O, and C=N bonds. The enantioselectivity of the reaction was strongly dependent on the substituent R at the position α to the ferrocene moiety. In many cases, both enantiomeric β-hydroxyesters of the reduction product can be obtained by simply replacing a dimethylamino group in the ligand with a methyl group.
- Ireland, Tania,Tappe, Katja,Grossheimann, Gabi,Knochel, Paul
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p. 843 - 852
(2007/10/03)
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- A strategy for the stereoselective synthesis of unsymmetric atropisomeric ligands: Preparation of NAPhePHOS, a new biaryl diphosphine
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MeO-NAPhePHOS represents the first example of a new series of atropisomeric diphosphines bearing heterotopic biaryl moieties. The key step of its synthesis is the diastereoselective, intramolecular, Cu1-promoted coupling of 1-iodonaphthol and 2-iodo-3-methoxyphenol connected by a chiral tether. (R,R)-2,4-Pentanediol is used as the chiral auxiliary in this highly selective reaction that leads to a single enantiomer of the title diphosphine. In the Ru-promoted hydrogenations of carbonyl derivatives, NAPhePHOS affords enantioselectivity enantioselectivity levels fully comparable to those of the C2-symmetrical analogues, BINAP and MeO-BIPHEP respectively, thus showing that the lack of C2 symmetry is not detrimental to the catalytic properties of atropisomeric ligands in these hydrogenation reactions.
- Michaud, Guillaume,Bulliard, Michel,Ricard, Louis,Genet, Jean-Pierre,Marinetti, Angela
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p. 3327 - 3330
(2007/10/03)
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- DERMATOLOGICAL COMPOSITIONS AND METHODS
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Disclosed are methods and compositions for regulating the melanin content of mammalian melanocytes; regulating pigmentation in mammalian skin, hair, wool or fur; treating or preventing various skin and proliferative disorders; by administration of various compounds, including alcohols, diols and/or triols and their analogues.
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- Highly enantioselective preparation of C2-symmetrical diols: Microbial hydrolysis of cyclic carbonates
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A new type of microbial enantioselective hydrolysis of C2-symmetrical cyclic carbonates is disclosed. During the screening test of the five-membered substrate (4,5-dimethyl-1,3-dioxolan-2-one 5), Pseudomonas diminuta was selected as the best strain to perform the stereoselective hydrolysis. The reaction of dl-5 with this microorganism in aqueous media containing THF as the co-solvent afforded (S,S)-5 and (R,R)-butanediol 1 in excellent yields. It was found that the ring size did not affect the reactivity and enantioselectivity although the enzyme had a high substrate specificity for the side chain. A six-membered cyclic carbonate, dl-4,6-dimethyl-1,3-dioxan-2-one 6, was smoothly hydrolyzed with higher enantioselectivity to afford the optically active (S,S)-6 and (R,R)-2,4-pentanediol 2. Copyright (C) 2000 Elsevier Science Ltd.
- Matsumoto, Kazutsugu,Sato, Youichi,Shimojo, Megumi,Hatanaka, Minoru
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p. 1965 - 1973
(2007/10/03)
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- Treatment of neurodegenerative diseases
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Disclosed are methods for increasing the differentiation of mammalian neuronal cells for purposes of treating neurodegenerative diseases or nerve damage by administration of various compounds including alcohols, diols and/or triols and their analogues.
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- Asymmetric hydrosilylation of ketones using trans-chelating chiral peralkylbisphosphine ligands bearing primary alkyl substituents on phosphorus atoms
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Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001 - 0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)- secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
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p. 485 - 496
(2007/10/03)
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- Enantioselective synthesis ofanti 1, 3-diols via ru(ii)-catalyzed hydrogénations
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The homogeneous ruthenium-catalyzed hydrogénation of new symmetrical 1, 3-diketones has been achieved with various ligands including SKEWPHOS and Me-DuPHOS. Complete conversions with enantiomeric and diastereomeric excesses up to 99% were obtained. This represents a new catalytic application of the chiral ligands above. Thieme Stuttgart.
- Blanc, Delphine,Ratovelomanana-Vidai, Virginie,Marinetti, Angela,Genêt, Jean-Pierre
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p. 480 - 482
(2007/10/03)
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- Chiral 1,2-bis(phosphetano)benzenes: Preparation and use in the Ru- catalyzed hydrogenations of carbonyl derivatives
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Chiral 1,2-bis(phosphetano)benzenes are readily prepared from accessible, optically pure 1,3-diol cyclic sulfates. Their ruthenium complexes catalyze the enantioselective hydrogenations of functionalized carbonyls with moderate-to-high enantiomeric excesses. High levels of diastereo- and enantioselectivity are achieved, especially in the hydrogenation of β-diketones to the corresponding anti-1,3-diols.
- Marinetti, Angela,Genet, Jean-Pierre,Jus, Sebastien,Blanc, Delphine,Ratovelomanana-Vidal, Virginie
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p. 1160 - 1165
(2007/10/03)
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- Treatment of diseases mediated by the nitric oxide/cGMP/protein kinase G pathway
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Disclosed are methods and compositions for stimulating cellular nitric oxide (NO) synthesis, cyclic guanosine monophosphate levels (cGMP), and protein kinase G (PKG) activity for purposes of treating diseases mediated by deficiencies in the NO/cGMP/PKG signal transduction pathway, by administration of various compounds including alcohols, diols and/or triols and their analogues.
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- The S(H)i reaction at silicon - A new entry into cyclic alkoxysilanes
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A new mild radical method for the preparation of cyclic five-membered alkoxysilanes is reported. This method comprises an intramolecular homolytic substitution reaction at silicon (S(H)i). Various leaving groups (SiMe3, GeMe3, SnMe3) were tested in the homolytic substitution reaction. We found that high yields were only obtained for silanes bearing a trimethyl-stannyl functionality as leaving group in the S(H)i reaction. Rate constants for the cyclization reaction were estimated by conducting standard competition experiments. Based on the kinetic data, more elaborate reaction sequences such as radical addition reactions with a subsequent S(H)i step were carried out. Stereoselective cyclization reactions were also investigated. Excellent 1,2 diastereoselectivities were observed. The products of the S(H)i reaction, cyclic alkoxysilanes, can easily be converted to the corresponding diol derivatives by Tamao-Fleming oxidation as demonstrated for several examples.
- Studer, Armido,Steen, Hanno
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p. 759 - 773
(2007/10/03)
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- An improved synthesis of chiral diols via the asymmetric catalytic hydrogenation of prochiral diones
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The rates of the asymmetric hydrogenation of prochiral diketones catalyzed by Ru(BINAP) catalysts were substantially accelerated in the presence of small amounts of a strong acid.
- Fan, Qing-Hua,Yeung, Chi-Hung,Chan, Albert S. C.
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p. 4041 - 4045
(2007/10/03)
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- Ruthenium(II) Complexes with the Atropisomeric Diphosphine 2,2'-Bis(diphenylphosphino)-6,6'-dimethylbiphenyl in the Enantioselective Hydrogenation of Pentane-2,4-dione
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The five-co-ordinate complex > reacts with pentane-2,4-dione (Hacac) in the presence of NEt3 to give >, which has been isolated in the solid state.The reaction of the chlorohydride > with Hacac gives > and eventually >, which were identified spectroscopically.The relevance of the formation of these new species to the enantioselective hydrogenation of 2,4-diketones to the corresponding diols has been studied by testing > and some of its derivatives as catalyst precursors, also in connection with the use of modifiers such as anhydrous HCl, PPh3, chloride ions, NEt3 and HBF4.The hydrogenation reaction has also been followed under ambient conditions by means of 31P and 1H NMR spectroscopy.The activity and selectivity data confirm that for optimum efficiency two chloride ligands must be present in the catalyst precursor.These data are discussed in view of the assessment of a possible reaction pathway for the catalytic reaction.
- Mezzetti, Antonio,Tschumper, Andreas,Consiglio, Giambattista
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- An Asymmetric Hydrogenation Sysytem Breeding Its Own Counter-configurated Ligand
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A homogeneous catalytic system based on Ruthenium-Skewphos complexes is presented, which breeds enantioselectively a precursor for the synthesis of Skewphos.In contrast to the known "self breeding" system of Prophos, this system generates the precursor for the opposite enantiomer of the ligand to enable access to both enantiomer of Skewphos after one and two cycles, respectively.
- Brunner, Henri,Terfort, Andreas
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p. 919 - 922
(2007/10/02)
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- Synthesis and Conformational Analysis of Six-Membered Cyclic Phenyl Phosphites
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A procedure for synthesizing potentially anancomeric equatorial phenyl phosphites (cis-1 and eq-cis-2) is reported.Spectral characteristics and low-temperature NMR studies on the phenyl phosphites suggest that eq-cis-2 is a system with a predominant chair conformation in solution.On the contrary, cis-1 is conformationally heterogeneous.
- Gordillo, Barbara,Garduno, Catalina,Guadarrama, Gerardo,Hernandez, Javier
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p. 5180 - 5185
(2007/10/02)
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- Stereoselective generation of 1,3- and 1,4-dioxy-substituted carbanions by sparteine-assisted deprotonation of chiral precursors: Substrate or reagent control in the synthesis of α, γ- and α,δ-diols
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The deprotonation of a dicarbamate, derived from (S)-butane-1,3-diol, by sec-butyllithium takes an highly diastereoselective, but opposite, direction in the presence of (-)-sparteine and of tetramethylethylenediamine (TMEDA), respectively. The (S)-pentane-1,4-diol derivative shows the same stereochemical preference under both conditions.
- Ahrens, Hartmut,Paetow, Mario,Hoppe, Dieter
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p. 5327 - 5330
(2007/10/02)
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- Diols obtained via chemo and regioselective ring opening of epoxy alcohols: A straightforward synthesis of 2S,3S-octandiol
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Epoxy alcohols are regio and chemoselectively opened to the corresponding iodohydrins and then reduced in situ to diols; the application of the described procedure leads to a short asymmetric of a well known pheromone. Also homoallylic (E and Z) epoxy alcohols and its benzylated derivatives shows high preference for regioselective opening affording the corresponding 1,3 diol.
- Bonini, Carlo,Righi, Giuliana
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p. 1531 - 1538
(2007/10/02)
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- (triphenylphosphine)dichlororuthenium(II): an Enantioselective Catalyst for the Hydrogenation of Diketones
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The novel species > 1 and 2-BH4)(PPh3)> 3 have been synthesized; 1 has a labile triphenylphosphine ligand and is a very active and enantioselective catalyst for the mono- or bis-hydrogenation of pentane-2,4-dione.
- Mezzetti, Antonio,Consiglio, Giambattista
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p. 1675 - 1677
(2007/10/02)
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- ASYMMETRISCHE KATALYSEN, 68. ENANTIOSELEKTIVE HYDRIERUNG VON ACETYLACETON MIT NaBr/L-(+)-WEINSAEURE MODIFIZIERTEN UEBERGANGSMETALLEN
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Enantioselective hydrogenation of acetylacetone AcacH to 4-hydroxy-2-pentanone HP and 2,4-pentanediol PD on various types of transition metal complexes modified with NaBr/L-(+)-tartaric acid was carried out.Finely divided catalysts prepared by cocondensation of the transition metals Cr, Mn, Fe, Co, Ni, the alloys Ni/Al, Ni/Zn, Ni/Cu, which were activated by NaOH treatment, and nickel powders with different surface areas were used.Transition metals and alloys obtained by condensation showed satisfactory enantioselectivity but had low hydrogenation activity.Modified nickel powders achieved high enantioselectivities and activities.The enantioselectivity could be correlated to the surface area of the nickel catalysts with a maximum between 5-7.5 m2/g.
- Brunner, H.,Amberger, K.,Wiehl, J.
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p. 571 - 584
(2007/10/02)
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- Synthesis of 1,2-Dimethylpyrene, 1,3-Dimethylpyrene and 1,2,3-Trimethylpyrene
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The title compounds have been prepared, starting from 1H-phenalene 1.The method described in this paper is an efficient procedure for introducing methyl groups into the A-ring of pyrene.
- Hempenius, Mark A.,Lugtenburg, Johan,Cornelisse, Jan
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p. 635 - 638
(2007/10/02)
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- A FACILE METHOD FOR THE PREPARATION OF 2,4-BIS(DIPHENYLPHOSPHINO)PENTANE(BDPP) ENENTIOMERS AND THEIR APPLICATION IN ASYMMETRIC HYDROGENATION
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Asymmetric heterogeneous hydrogenation of acetylacetone was applied for the preparation of both enantiomers (2R,4R and 2S,4S) of 2,4-bis(diphenylphosphino)pentane (BDPP).Among the chiral phosphine prepared up to now BDPP appears to be unique in the sense that its rhodium(I) complexes serve as effective homogeneous asymmetric hyrogenation catalysts not only for the reduction Z-α-amidoacrylic acids but also for the reduction of α-ethylstyrene, acetophenone, and acetophenonebenzylimine.The analogous phosphinite ligand BDPOP yields a less active catalyst
- Bakos, Jozsef,Toth, Imre,Heil, Balint,Marko, Laszlo
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- Stereochemical Studies of the Hydrogenation with an Asymmetrically Modified Raney Nickel Catalyst. The Hydrogenation of Acetylacetone
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The hydrogenation of acetylacetone (I) over asymmetrically modified Raney nickel (MRNi) proceeded, step by step, as follows: Step 1 Step 2 acetylacetone (I) ------> 4-hydroxy-2-pentanone (III) ------> 2,4-pentanediol (II).It was demonstrated that the optical yield of Step 1 and the diastereomer excess of Step 2 are governed by the ratio of the stereo-differentiating reaction site to the non-stereo-differentiating reaction site on the catalyst.The stereochemistry of each step was also discussed based on the mode of the intermolecular hydrogen bondings between the substrate and tartaric acid adsorbed on the catalyst.RNi modified with a mixture of tartaric acid and NaBr (TA-NaBr-MRNi) gave the best result with respect to both Step 1 and Step 2.
- Tai, Akira,Ito, Kazuhisa,Harada, Tadao
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p. 223 - 227
(2007/10/02)
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