- Transformation of organic compounds in the presence of metal complexes. IV. Hydrosilylation of 2- and 4-alkylcyclohexanones on rhodium(I) complexes
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The hydrosilylation of 2- and 4-alkylcyclohexanones with Ph2SiH2 was studied under various conditions.The isomeric distribution of the resulting alcohols, i.e. the stereochemistry of the hydrosilylation, is influenced by the position and size of the alkyl groups, the catalyst concentration, the reaction temperature, and the types of ligand attached.
- Felfoeldi, K.,Kapocsi, I.,Bartok, M.
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- Potassium Triphenylborohydride. A New Reducting Agent for the Reduction of Carbonyl Compounds with an Exceptional Stereo- and Chemoselectivity
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Potassium triphenylborohydride (KTPBH), a highly hindered potassium triarylborohydride prepared from triphenylborane and potassium hydride, exhibits remarkable stereo- and chemoselectivity for the reduction of carbonyl compounds.KTPBH reduces 2-methylcyclohexanone to give cis-2-methylcyclohexanol with an excellent stereospecificity (98.5:1.5), approaching that of lithium tri-sec-butylborohydride.KTPBH also shows a remarkable chemoselectivity.It shows 97:3 selectivity between cyclohexanone and cyclopentanone and 99.4:0.6 selectivity between cyclohexanone and 4-heptanone.This chemoselectivity is comparable to those achieved by lithium di-n-butyl-9-BBN and tert-butylamine-borane, the best two reagents reported for such purposes.KTPBH is stable over 2 months at room temperature, and this reagent possesses a practical advantage in the isolation of the alcohol product without oxidation and distillation.
- Yoon, Nung Min,Kim, Kwan Eung,Kang, Jahyo
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- Addition Compounds of Alkali Metal Hydrides. 27. A General Method for Preparation of the Potassium 9-Alkoxy-9-boratabicyclononanes. A New Class of Stereoselective Reducing Agents
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The reaction in tetrahydrofuran of potassium hydride with representative B-alkoxy-9-borabicyclononanes (B-OR-9-BBN) containing alkoxy groups with increasing steric requirements was examined in detail to establish the generality of this synthesis of the corresponding potassium 9-alkoxy-9-boratabicyclononanes (K9-OR-9-BBNH) and the stereoselectivities of these new reagents for the reduction of cyclic ketones.For R = Me and n-Bu, the reactions with potassium hydride are very fast, almost instantaneous, even at 0 deg C.However, the products are unstable and rapidly undergo redistribution, even in the presence of excess potassium hydride.Moderately hindered alkoxy derivatives, R = 2-Pr and 2-Bu, react somewhat slower (1 h at 0 deg C and 25 deg C, respectively) and the products are stable to redistribution.More hindered alkoxy derivatives, R = t-Bu, t-Am, Thx, require 24 h at 25 deg C.Even more hindered alkoxy groups, R = 3-ethyl-3-pentyl and 2,4-dimethyl-2-pentyl, require even longer reaction times and higher temperatures.All reagents show high stereoselectivities in the reduction of cyclic ketones, with the stereoselectivities generally increasing with increasing steric requirements of the alkoxy substituent.The thexyl derivative appears especially favorable, with the byproducts of the reaction readily removed from the reaction mixture.
- Brown, Herbert C.,Cha, Jin Soon,Nazer, Behrooz,Brown, Charles A.
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- Epoxide opening with organocuprates and grignard reagents in the presence of chiral ligands
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The reaction of cyclohexene oxide with organocuprates and Grignard reagents in the presence of chiral ligands to give chiral β-substituted alcohols in low optical yields is described.
- Davies, Stephen G.,Wollowitz, Susan
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- Addition Compounds of Alkali Metal Hydrides. 28. Preparation of Potassium Dialkoxymonoalkylborohydrides from Cyclic Boronic Esters. A New Class of Reducing Agents
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The reaction of cyclic boronic esters possesing a wide range of steric requirements with excess potassium hydride to form the corresponding potassium dialkoxymonoalkylborohydrides was explored.In case involving a less hindered diol such as ethylene glycol, 2,3-butanediol, or 1,3-propanediol, the reaction is slightly exothermic and quite facile, being complete in less than 1 h at 25 deg C.In the case involving a highly hindered diol such as pinacol, the reaction is very sluggish, even at 65 deg C.The stability of the potassium dialkoxymonoalkylborohydrides is strongly dependent upon the steric bulkiness of the alkyl groups of the boronic ester.Thus, for R = n-hexyl, 3-hexyl, tert-butyl, or thexyl, the addition product is quite stable to disproportionation.However, for R = methyl, the corresponding borohydride is unstable, undergoing rapid redistribution to form a white precipitate.The stable potassium dialkoxymonoalkylborohydrides thus formed reduce 2-methylcyclohexanone with moderate stereoselectivity, giving the cis isomer preferentially, with selectivities of 73-84percent
- Brown, Herbert C.,Park, Won Suh,Cha, Jin Soon,Cho, Byung Tae,Brown, Charles A.
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- Cobalt-Nanoparticles Catalyzed Efficient and Selective Hydrogenation of Aromatic Hydrocarbons
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The development of inexpensive and practical catalysts for arene hydrogenations is key for future valorizations of this general feedstock. Here, we report the development of cobalt nanoparticles supported on silica as selective and general catalysts for such reactions. The specific nanoparticles were prepared by assembling cobalt-pyromellitic acid-piperazine coordination polymer on commercial silica and subsequent pyrolysis. Applying the optimal nanocatalyst, industrial bulk, substituted, and functionalized arenes as well as polycyclic aromatic hydrocarbons are selectively hydrogenated to obtain cyclohexane-based compounds under industrially viable and scalable conditions. The applicability of this hydrogenation methodology is presented for the storage of H2 in liquid organic hydrogen carriers.
- Murugesan, Kathiravan,Senthamarai, Thirusangumurugan,Alshammari, Ahmad S.,Altamimi, Rashid M.,Kreyenschulte, Carsten,Pohl, Marga-Martina,Lund, Henrik,Jagadeesh, Rajenahally V.,Beller, Matthias
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p. 8581 - 8591
(2019/09/12)
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- Demystifying Cp2Ti(H)Cl and Its Enigmatic Role in the Reactions of Epoxides with Cp2TiCl
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The role of Cp2Ti(H)Cl in the reactions of Cp2TiCl with trisubstituted epoxides has been investigated in a combined experimental and computational study. Although Cp2Ti(H)Cl has generally been regarded as a robust species, its decomposition to Cp2TiCl and molecular hydrogen was found to be exothermic (ΔG = -11 kcal/mol when the effects of THF solvation are considered). In laboratory studies, Cp2Ti(H)Cl was generated using the reaction of 1,2-epoxy-1-methylcyclohexane with Cp2TiCl as a model. Rapid evolution of hydrogen gas was demonstrated, indicating that Cp2Ti(H)Cl is indeed a thermally unstable molecule, which undergoes intermolecular reductive elimination of hydrogen under the reaction conditions. The stoichiometry of the reaction (Cp2TiCl:epoxide = 1:1) and the quantity of hydrogen produced (1 mol per 2 mol of epoxide) is consistent with this assertion. The diminished yield of allylic alcohol from these reactions under the conditions of protic versus aprotic catalysis can be understood in terms of the predominant titanium(III) present in solution. Under the conditions of protic catalysis, Cp2TiCl complexes with collidine hydrochloride and the titanium(III) center is less available for "cross-disproportionation" with carbon-centered radicals; this leads to byproducts from radical capture by hydrogen atom transfer, resulting in a saturated alcohol.
- Gordon, Jonathan,Hildebrandt, Sven,Dewese, Kendra R.,Klare, Sven,Gans?uer, Andreas,Rajanbabu,Nugent, William A.
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supporting information
p. 4801 - 4809
(2019/01/08)
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- (Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
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Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
- Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
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supporting information
p. 1460 - 1464
(2018/04/06)
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- Mild and Regioselective Hydroxylation of Methyl Group in Neocuproine: Approach to an N,O-Ligated Cu6 Cage Phenylsilsesquioxane
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The self-Assembly synthesis of Cu(II)-silsesquioxane involving 2,9-dimethyl-1,10-phenanthroline (neocuproine) as an additional N ligand at copper atoms was performed. The reaction revealed an unprecedented aerobic hydroxylation of only one of the two methyl groups in neocuproine to afford the corresponding geminal diol. The produced derivative of oxidized neocuproine acts as a two-centered N,O ligand in the assembly of the hexacopper cage product [Cu6(Ph5Si5O10)2·(C14H11N2O2)2] (1), coordinating two of the six copper centers in the product. Two siloxanolate ligands [PhSi(O)O]5 in the cis configuration coordinate to the rest of the copper(II) ions. Compound 1 is a highly efficient homogeneous precatalyst in the oxidation of alkanes and alcohols with peroxides.
- Bilyachenko, Alexey N.,Levitsky, Mikhail M.,Khrustalev, Victor N.,Zubavichus, Yan V.,Shul'Pina, Lidia S.,Shubina, Elena S.,Shul'Pin, Georgiy B.
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supporting information
p. 168 - 171
(2018/02/06)
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- Asymmetric Induction via a Helically Chiral Anion: Enantioselective Pentacarboxycyclopentadiene Br?nsted Acid-Catalyzed Inverse-Electron-Demand Diels-Alder Cycloaddition of Oxocarbenium Ions
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An enantioselective catalytic inverse-electron-demand Diels-Alder reaction of salicylaldehyde acetal-derived oxocarbenium ions and vinyl ethers to generate 2,4-dioxychromanes is described. Chiral pentacarboxycyclopentadiene (PCCP) acids are found to be effective for a variety of substrates. Computational and X-ray crystallographic analyses support the unique hypothesis that an anion with point-chirality-induced helical chirality dictates the absolute sense of stereochemistry in this reaction.
- Gheewala, Chirag D.,Hirschi, Jennifer S.,Lee, Wai-Hang,Paley, Daniel W.,Vetticatt, Mathew J.,Lambert, Tristan H.
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supporting information
p. 3523 - 3527
(2018/03/21)
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- Heptanuclear Fe5Cu2-Phenylgermsesquioxane containing 2,2′-Bipyridine: Synthesis, Structure, and Catalytic Activity in Oxidation of C-H Compounds
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A new representative of an unusual family of metallagermaniumsesquioxanes, namely the heterometallic cagelike phenylgermsesquioxane (PhGeO2)12Cu2Fe5(O)OH(PhGe)2O5(bipy)2 (2), was synthesized and structurally characterized. Fe(III) ions of the complex are coordinated by oxa ligands: (i) cyclic (PhGeO2)12 and acyclic (Ph2Ge2O5) germoxanolates and (ii) O2- and (iii) HO- moieties. In turn, Cu(II) ions are coordinated by both oxa (germoxanolates) and aza ligands (2,2′-bipyridines). This "hetero-type" of ligation gives in sum an attractive pagoda-like molecular architecture of the complex 2. Product 2 showed a high catalytic activity in the oxidation of alkanes to the corresponding alkyl hydroperoxides (in yields up to 30%) and alcohols (in yields up to 100%) and in the oxidative formation of benzamides from alcohols (catalyst loading down to 0.4 mol % in Cu/Fe).
- Bilyachenko, Alexey N.,Khrustalev, Victor N.,Zubavichus, Yan V.,Shul'Pina, Lidia S.,Kulakova, Alena N.,Bantreil, Xavier,Lamaty, Frédéric,Levitsky, Mikhail M.,Gutsul, Evgeniy I.,Shubina, Elena S.,Shul'Pin, Georgiy B.
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p. 528 - 534
(2018/01/11)
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- Catalytic carbonyl hydrosilylations: Via a titanocene borohydride-PMHS reagent system
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Reduction of a wide range of aldehydes and ketones with catalytic amounts of titanocene borohydride in concert with a stoichiometric poly(methylhydrosiloxane) (PMHS) reductant is reported. Preliminary mechanistic studies demonstrate that the reaction is mediated by a reactive titanocene(iii) complex, whose oxidation state remains constant throughout the reaction.
- Fianu, Godfred D.,Schipper, Kyle C.,Flowers, Robert A.
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p. 3469 - 3473
(2017/08/21)
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- Synthesis, structures and catalytic activity of p-tolylimido rhenium(V) complexes incorporating quinoline-derived ligands
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p-Tolylimido rhenium(V) complexes, trans-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(4-MeO-quin-2-COO)(PPh3)] (1), trans-(Br,Br)-[Re(p-NC6H4CH3)Br2(4-MeO-quin-2-COO)(PPh3)]·2MeCN (2), trans-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(isoquin-1-COO)(PPh3)] (3), trans-(Br,Br)-[Re(p-NC6H4CH3)Br2(isoquin-1-COO)(PPh3)] (4), cis-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(4-MeO-quin-2-COO)(PPh3)] (5), cis-(Br,Br)-[Re(p-NC6H4CH3)Br2(4-MeO-quin-2-COO)(PPh3)]·MeOH (6), cis-(Cl,Cl)-[Re(p-NC6H4CH3)Cl2(isoquin-1-COO)(PPh3)] (7) and cis-(Br,Br)-[Re(p-NC6H4CH3)Br2(isoquin-1-COO)(PPh3)] (8), have been synthesized and characterized using X-ray analysis and spectroscopic methods (IR,1H,13C and31P NMR, UV–Vis). To elucidate the structural, spectroscopic and bonding properties, the theoretical calculations at the DFT level were undertaken for 1, 3, 5 and 7. The synthesized complexes exhibited moderate activity in the oxidation of 1-phenylethanol and certain alkanes (n-heptane and methylcyclohexane) with tert-butyl hydroperoxide (TBHP) in acetonitrile. Chromatograms of products obtained from the alkanes indicated that a sufficient sterical hindrance exists around of the rhenium catalytic center.
- Gryca,Machura,Shul'pina, Lidia S.,Shul'pin, Georgiy B.
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supporting information
p. 683 - 695
(2016/12/02)
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- Carboxylic group embedded carbon balls as a new supported catalyst for hydrogen economic reactions
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Carboxylic group functionalized carbon balls have been successfully synthesized by using a facile synthesis method and well characterized with different characterization techniques such as XPS, MAS NMR, SEM, ICP and N2 physi-sorption analysis. The synthesized material has been effectively utilized as novel support to immobilized ruthenium catalyst for hydrogen economic reactions.
- Bordoloi, Ankur
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p. 3071 - 3076
(2016/03/19)
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- A non-dissociative open-flask hydroboration with ammonia borane: Ready synthesis of ammonia-trialkylboranes and aminodialkylboranes
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Under open-flask conditions, ammonia borane hydroborates olefins in refluxing tetrahydrofuran. Unlike conventional hydroboration, the Lewis base (ammonia) is not dissociated from the boron center. Terminal alkenes selectively provide ammonia-trialkylborane complexes. On the other hand, internal alkenes afford aminodialkylboranes via a metal-free hydroboration-dehydrogenation sequence. Alkaline hydrogen peroxide oxidation of the products provides the corresponding alcohols in high yields.
- Ramachandran, P. Veeraraghavan,Drolet, Michael P.,Kulkarni, Ameya S.
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p. 11897 - 11900
(2016/10/09)
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- Novel cage-like hexanuclear nickel(II) silsesquioxane. Synthesis, structure, and catalytic activity in oxidations with peroxides
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New hexanuclear nickel(II) silsesquioxane [(PhSiO1.5)12(NiO)6(NaCl)] (1) was synthesized as its dioxane-benzonitrile-water complex (PhSiO1,5)12(NiO)6(NaCl)(C4H8O2)13(PhCN)2(H2O)2 and studied by X-ray and topological analysis. The compound exhibits cylinder-like type of molecular architecture and represents very rare case of polyhedral complexation of metallasilsesquioxane with benzonitrile. Complex 1 exhibited catalytic activity in activation of such small molecules as light alkanes and alcohols. Namely, oxidation of alcohols with tert-butylhydroperoxide and alkanes with meta-chloroperoxybenzoic acid. The oxidation of methylcyclohexane gave rise to the isomeric ketones and unusual distribution of alcohol isomers.
- Bilyachenko, Alexey N.,Yalymov, Alexey I.,Shul'pina, Lidia S.,Mandelli, Dalmo,Korlyukov, Alexander A.,Vologzhanina, Anna V.,Es'kova, Marina A.,Shubina, Elena S.,Levitsky, Mikhail M.,Shul'pin, Georgiy B.
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- Facile arene hydrogenation under flow conditions catalyzed by rhodium or ruthenium on carbon
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An efficient and practical protocol for the flow hydrogenation of aromatic rings was developed. The hydrogenation of a variety of aromatic compounds, such as benzene, furan, and pyridine derivatives, could be completed within only 20 s during a single pass through a catalyst cartridge containing 10 % rhodium on carbon (Rh/C) or 10 % ruthenium on carbon (Ru/C) under neutral conditions. The protocol was successfully applied to a 10 mmol scale reaction. Furthermore, the 10 % Rh/C and 10 % Ru/C did not deteriorate during the entire study.
- Hattori, Tomohiro,Ida, Takashi,Tsubone, Aya,Sawama, Yoshinari,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 2492 - 2497
(2015/04/22)
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- Catalyst and process for hydrogenating aromatics
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The present invention relates to an eggshell catalyst comprising an active metal selected from the group consisting of ruthenium, rhodium, palladium, platinum and mixtures thereof, applied to a support material comprising silicon dioxide, wherein the pore volume of the support material is 0.6 to 1.0 ml/g, determined by Hg porosimetry, the BET surface area is 280 to 500 m2/g, and at least 90% of the pores present have a diameter of 6 to 12 nm, to a process for preparing this eggshell catalyst, to a process for hydrogenating an organic compound which comprises at least one hydrogenatable group using the eggshell catalyst, and to the use of the eggshell catalyst for hydrogenating an organic compound.
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Page/Page column 20
(2015/07/27)
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- The Stereoselective Reductions of Ketones to the Most Thermodynamically Stable Alcohols Using Lithium and Hydrated Salts of Common Transition Metals
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A simple method is presented for the highly stereoselective reductions of ketones to the most thermodynamically stable alcohols. In this procedure, the ketone is treated with lithium dispersion and either FeCl2·4H2O or CuCl2·2H2O in THF at room temperature. This protocol is applied to a large number and variety of ketones and is both more convenient and efficient than those commonly reported for the diastereoselective reduction of five- and six-membered cyclic ketones.
- Kennedy, Nicole,Cohen, Theodore
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p. 8134 - 8141
(2015/09/02)
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- Diastereoselective and Enantioselective Silylation of 2-Arylcyclohexanols
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The silylation-based kinetic resolution of trans 2-arylcyclohexanols was accomplished by employing a triaryl silyl chloride as the derivatizing reagent with a commercially available isothiourea catalyst. The methodology is selective for the trans diastereomer over the cis, which provides an opportunity to selectively derivatize one stereoisomer out of a mixture of four. By employing this technology, a facile, convenient method to form a highly enantiomerically enriched silylated alcohol was accomplished through a one-pot reduction-silylation sequence that started with a 2-aryl-substituted ketone.
- Wang, Li,Akhani, Ravish K.,Wiskur, Sheryl L.
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supporting information
p. 2408 - 2411
(2015/05/27)
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- P-Tolylimido rhenium(v) complexes with phenolate-based ligands: Synthesis, X-ray studies and catalytic activity in oxidation with tert-butylhydroperoxide
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The reactions of mer-[Re(p-NTol)X3(PPh3)2] (X = Cl, Br) with chelating phenolate-based ligands (2-(2-hydroxy-5-methylphenyl)benzotriazole (HL1), 2-(2-hydroxyphenyl)benzothiazole (HL2) or 2-(2-hydroxyphenyl)benzoxazole (HL3)) afforded a series of p-tolylimido rhenium(v) complexes cis- or trans-(X,X)-[Re(p-NTol)X2(L)(PPh3)]·yMeCN (where X = Cl, Br; L = L1, L2, L3 and y = 0-2) and [Re(p-NTol)X(L)(PPh3)2]Z·pPPh3 (where X = Cl, Br; Z = ReO4, PF6; L = L1, L2, L3 and p = 0 or 1). The reported compounds were characterized by elemental analysis, FT-IR, NMR (1H, 13C and 31P) and X-ray crystallography. Interestingly, the halide ions of [Re(p-NTol)Cl2(L1)(PPh3)]·MeCN (1) and [Re(p-NTol)Cl2(L2)(PPh3)]·2MeCN (3) are in cis relative dispositions, whereas the complexes [Re(p-NTol)Br2(L)(PPh3)] (L1 for 2, L2 for 4 and L3 for 6) and [Re(p-NTol)Cl2(L3)(PPh3)] (5) were found to be trans-(X,X) isomers. The compounds [Re(p-NTol)X(L)(PPh3)2](PF6) (X = Cl, Br; L = L1 and L2) and [Re(p-NTol)X(L3)(PPh3)2](PF6)·PPh3 (X = Cl, Br) have been tested in oxidative catalysis. A few compounds exhibited very good catalytic properties in oxidation of alcohols with tert-BuOOH (TBHP) in acetonitrile solution at moderate temperatures. Complex [Re(p-NTol)Cl(L2)(PPh3)2]PF6 (13) is the catalyst of choice for oxidation of 1-phenylethanol to acetophenone (in 80% yield; turnover number attained 290 after 30 h) and cyclooctanol to cyclooctanone (in 88% yield). Notably lower activity has been found in the oxidation of alkanes with TBHP. Product distribution in the oxidation of methylcyclohexane indicates some steric hindrance around the reaction center.
- Gryca, Izabela,Machura, Barbara,Malecki, Jan Grzegorz,Kusz, Joachim,Shul'Pina, Lidia S.,Ikonnikov, Nikolay S.,Shul'Pin, Georgiy B.
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p. 334 - 351
(2015/12/26)
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- Alkane oxidation with peroxides catalyzed by cage-like copper(II) silsesquioxanes
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Isomeric cage-like tetracopper(II) silsesquioxane complexes [(PhSiO1.5)12(CuO)4(NaO0.5)4] (1a), [(PhSiO1.5)6(CuO)4(NaO0.5)4(PhSiO1.5)6] (1b) and binuclear complex [(PhSiO1.5)10(CuO)2(NaO0.5)2] (2) have been studied by various methods. These compounds can be considered as models of some multinuclear copper-containing enzymes. Compounds 1a and 2 are good pre-catalysts for the alkane oxygenation with hydrogen peroxide in air in an acetonitrile solution. Thus, the 1a-catalyzed reaction with cyclohexane at 60°C gave mainly cyclohexyl hydroperoxide in 17% yield (turnover number, TON, was 190 after 230 min and initial turnover frequency, TOF, was 100 h-1). The alkyl hydroperoxide partly decomposes in the course of the reaction to afford the corresponding ketone and alcohol. The effective activation energy for the cyclohexane oxygenation catalyzed by compounds 1a and 2 is 16 ± 2 and 17 ± 2 kcal mol-1, respectively. Selectivity parameters measured in the oxidation of linear and branched alkanes and the kinetic analysis revealed that the oxidizing species in the reaction is the hydroxyl radical. The analysis of the dependence of the initial reaction rate on the initial concentration of cyclohexane led to a conclusion that hydroxyl radicals attack the cyclohexane molecules in proximity to the copper reaction centers. The oxidations of saturated hydrocarbons with tert-butylhydroperoxide (TBHP) catalyzed by complexes 1a and 2 exhibit unusual selectivity parameters which are due to the steric hindrance created by bulky silsesquioxane ligands surrounding copper reactive centers. Thus, the methylene groups in n-octane have different reactivities: the regioselectivity parameter for the oxidation with TBHP catalyzed by 1a is 1:10.5:8:7. Furthermore, in the oxidation of methylcyclohexane the position 2 relative to the methyl group of this substrate is noticeably less reactive than the corresponding positions 3 and 4. Finally, the oxidation of trans-1,2-dimethylcyclohexane with TBHP catalyzed by complexes 1a and 2 proceeds stereoselectively with the inversion of configuration. The 1a-catalyzed reaction of cyclohexane with H216O2 in an atmosphere of 18O2 gives cyclohexyl hydroperoxide containing up to 50% of 18O. The small amount of cyclohexanone, produced along with cyclohexyl hydroperoxide, is 18O-free and is generated apparently via a mechanism which does not include hydroxyl radicals and incorporation of molecular oxygen from the atmosphere.
- Vinogradov, Mikhail M.,Kozlov, Yuriy N.,Bilyachenko, Alexey N.,Nesterov, Dmytro S.,Shul'pina, Lidia S.,Zubavichus, Yan V.,Pombeiro, Armando J. L.,Levitsky, Mikhail M.,Yalymov, Alexey I.,Shul'pin, Georgiy B.
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supporting information
p. 187 - 199
(2015/02/19)
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- Cytochrome P450 catalyzed oxidative hydroxylation of achiral organic compounds with simultaneous creation of two chirality centers in a single C-H activation step
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Regio- and stereoselective oxidative hydroxylation of achiral or chiral organic compounds mediated by synthetic reagents, catalysts, or enzymes generally leads to the formation of one new chiral center that appears in the respective enantiomeric or diastereomeric alcohols. By contrast, when subjecting appropriate achiral compounds to this type of C-H activation, the simultaneous creation of two chiral centers with a defined relative and absolute configuration may result, provided that control of the regio-, diastereo-, and enantioselectivity is ensured. The present study demonstrates that such control is possible by using wild type or mutant forms of the monooxygenase cytochrome P450 BM3 as catalysts in the oxidative hydroxylation of methylcyclohexane and seven other monosubstituted cyclohexane derivatives.
- Roiban, Gheorghe-Doru,Agudo, Ruben,Reetz, Manfred T.
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supporting information
p. 8659 - 8663
(2014/08/18)
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- New p-tolylimido rhenium(v) complexes with carboxylate-based ligands: Synthesis, structures and their catalytic potential in oxidations with peroxides
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Novel p-tolylimido rhenium(v) complexes trans-(Cl,Cl)-[Re(p-NC 6H4CH3)Cl2(pyz-2-COO)(PPh 3)]·MeCN (1), trans-(Cl,Cl)-[Re(p-NC6H 4CH3)Cl2(pyz-2-COO)(PPh
- Gryca,MacHura,Malecki,Shul'Pina, Lidia S.,Pombeiro, Armando J. L.,Shul'Pin, Georgiy B.
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p. 5759 - 5776
(2014/04/03)
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- NHC-stabilized ruthenium nanoparticles as new catalysts for the hydrogenation of aromatics
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The application of ruthenium nanoparticles (RuNPs) stabilized by the N-heterocyclic carbenes (NHC) N,N′-di(tert-butyl)imidazol-2-ylidene (ItBu) and 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene IPr as catalysts in the hydrogenation of several substrates is reported under various reaction conditions (solvent, substrate concentration, substrate/metal ratio, temperature). The RuNHC nanoparticles are active catalysts in the hydrogenation of aromatics and show an interesting ligand effect, RuIPr NPs being generally more active than RuItBu. The Royal Society of Chemistry 2013.
- Gonzalez-Galvez, David,Lara, Patricia,Rivada-Wheelaghan, Orestes,Conejero, Salvador,Chaudret, Bruno,Philippot, Karine,Van Leeuwen, Piet W.N.M.
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- Abnormal N-heterocyclic carbene-phosphine ruthenium(II) complexes as active catalysts for transfer hydrogenation
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The bifunctional phosphine-abnormal N-heterocyclic carbene ruthenium(II) complex RuBr(OAc)(PPh3)(P-aNHC) (1) has been synthesized in high yield by reaction of Ru(OAc)2(PPh3)2 with a phosphine imidazolium bromide (P-NHC × HBr) and characterized by X-ray diffraction. This compound shows high catalytic activity for the transfer hydrogenation of ketones to alcohols in 2-propanol. Rate and efficiency of 1 can be enhanced by the addition of ethylenediamine or benzylamine, affording TOFs up to 140 000 h-1. Reaction of 1 with ethylenediamine leads to the Ru carbene/amine complex [Ru(OAc)(PPh3)(P-aNHC)(H2NCH 2CH2NH2)]Br (2), which displays the same activity of the in situ generated species.
- Witt, Julia,Poethig, Alexander,Kuehn, Fritz E.,Baratta, Walter
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p. 4042 - 4045
(2013/09/02)
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- Structural characterization and oxidation reactivity of a nickel(II) acylperoxo complex
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The nickel(II)-acylperoxo complex [Ni(TpCF3Me) (κ2-mCPBA)] (1CF3Me) [TpCF3Me = hydrotris(3-trifluoromethyl-5-methylpyrazolyl)borate, mCPBA = m-chloroperbenzoate] was isolated and fully characterized. The electrophilic oxygenation ability of 1CF3Me toward sulfides and olefins was confirmed. The Michaelis-Menten-type behavior of thioanisole oxygenation indicates the existence of a pre-equilibrium of substrate association in the reaction. In addition, 1CF3Me retains H-atom abstraction ability for hydrocarbons with activated methylene C-H bonds (e.g., fluorene). The oxidations of styrenes and these readily oxidizable hydrocarbons follow second-order kinetics, first-order each with respect to 1CF3Me and substrate. The lack of clear acceleration in the decay of 1CF3Me in the presence of substrates with high C-H bond dissociation energies (e.g., cyclohexane) suggests that another reaction pathway contributes through the O-O-cleaved intermediate.
- Nakazawa, Jun,Terada, Shota,Yamada, Masaki,Hikichi, Shiro
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supporting information
p. 6010 - 6013
(2013/06/04)
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- A multifunction Pd/Sc(OTf)3/ionic liquid catalyst system for the tandem one-pot conversion of phenol to ε-caprolactam
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A multifunction Pd/Sc(OTf)3/ionic liquid catalyst for the tandem one-pot conversion of phenol to ε-caprolactam is reported. Pd and Sc(OTf)3 cooperate to catalyze the hydrogenation of phenol to cyclohexanone with excellent conversion (>99.9%) and selectivity (>99.9%), whereas Sc(OTf)3 and an ionic liquid, [bmim][PF6], cooperate to catalyze the tandem transformation of the resulting cyclohexanone to cyclohexanone oxime and the Beckmann rearrangement affording ε-caprolactam.
- Shin, Ju Yeon,Jung, Da Jung,Lee, Sang-Gi
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supporting information
p. 525 - 528
(2013/05/09)
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- Air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds as transfer reduction and oxidation catalysts
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A series of air-stable, nitrile-ligated (cyclopentadienone)iron dicarbonyl compounds was synthesized and their activities as catalysts in the transfer reduction of acetophenone were explored. While all were active catalysts, the acetonitrile adduct was chosen for further study and was found to be active in the transfer reduction of aldehydes and ketones and in the Oppenauer-type oxidation of secondary alcohols. The acetonitrile catalyst exhibited activities similar to those of an analogous air-sensitive iron hydride, but unlike the iron hydride it was unreactive in carbonyl reductions using hydrogen gas. Copyright
- Plank, Taylor N.,Drake, Jessica L.,Kim, Daniel K.,Funk, Timothy W.
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supporting information; experimental part
p. 597 - 601
(2012/05/04)
-
- CYCLIC AMINE-1-CARBOXYLIC ACID ESTER DERIVATIVE AND PHARMACEUTICAL COMPOSITION CONTAINING THE SAME
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Provided is a compound useful as a therapeutic drug for pain and inflammation caused by various pathological conditions such as neuropathic pain and rheumatoid arthritis. The compound of the formula (I) or a salt thereof [wherein R1 is a methyl group or a hydrogen atom, R2 represents a hydrogen atom, an alkyl group, an alkylcarbonyl group or an aryl carbonyl group, A represents a cycloalkyl group, a cycloalkenyl group, an aryl group or a heteroaryl group (each group may be substituted with a substituent selected from the group consisting of alkyl, alkenyl, cycloalkyl and halogen), n and m each represent an integer of 1, 2 or 3, and p represents an integer of 0, 1, 2 or 3].
- -
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-
- Alkoxide-catalyzed reduction of ketones with pinacolborane
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The reduction of ketones with pinacolborane (4,4,5,5-tetramethyl-1,3,2- dioxaborolane) is catalyzed by 5 mol % NaOt-Bu at ambient temperature. The reaction is high yielding and general, providing complete conversion of aryl and dialkyl ketones. Although spectroscopic studies of the active hydride source in benzene-d6 were complicated due to poor solubility, the data are consistent with the active hydride source being the trialkoxyborohydride, which is believed to be present in low concentration under the reaction conditions. Performing analogous studies in tetrahydrofuran resulted in a complex equilibrium between several different boron-containing species in which the trialkoxyborohydride compound was the major species.
- Query, Ian P.,Squier, Phillip A.,Larson, Emily M.,Isley, Nicholas A.,Clark, Timothy B.
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experimental part
p. 6452 - 6456
(2011/09/16)
-
- Selective reduction of organic compounds with Al- trifluoromethanesulfonyldiisobutylalane. Comparison of its reactivity with Al-methanesulfonyldiisobutylalane
-
The new MPV type reagent, Al-trifluoromethanesulfonyldiisobutylalane (DIBAO3SCF3), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined, and compared its reactivity with that of Al-methanesulfonyldiisobutylalane (DIBAO3SCH 3) in order to understand the fluorine-substituent effect on its reactivity. In general, the reactivity of DIBAO3SCF3 appears to be much higher than that of DIBAO3SCH3, apparently due to the acidity increase by the electron-withdrawing fluorine-substituent. The reagent reduced aldehydes and ketones readily, but showed a perfect selectivity in the reduction of α,β-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in an absolutely 100% purity. In addition, the reagent achieved the regioselective cleavage of phenyl-or/and alkyl-substituted epoxides to the less substituted alcohols in a perfect regioselectivity. Moreover, the reagent also showed an high stereoselectivity in the reduction of substituted cycloalkanones to produce the thermodynamically more stable alcohol epimers exclusively.
- Cha, Jin Soon
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experimental part
p. 219 - 224
(2011/11/06)
-
- CYCLIC AMINE-1-CARBOXYLIC ACID ESTER DERIVATIVE AND PHARMACEUTICAL COMPOSITION CONTAINING THE SAME
-
Provided is a compound useful as a therapeutic drug for pain and inflammation caused by various pathological conditions such as neuropathic pain and rheumatoid arthritis. The compound of the formula (I) or a salt thereof [wherein R1 is a methyl group or a hydrogen atom, R2 represents a hydrogen atom, an alkyl group, an alkylcarbonyl group or an aryl carbonyl group, A represents a cycloalkyl group, a cycloalkenyl group, an aryl group or a heteroaryl group (each group may be substituted with a substituent selected from the group consisting of alkyl, alkenyl, cycloalkyl and halogen), n and m each represent an integer of 1, 2 or 3, and p represents an integer of 0, 1, 2 or 3].
- -
-
Page/Page column 25-26
(2011/02/19)
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- Selective reduction of organic compounds with Al- methanesulfonyldiisobutylalane
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The new MPV type reagent, Al-methanesulfonyldiisobutylalane (DIBAO 3SCH3), has been prepared and its reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined in order to find out a new reducing system with high selectivity in organic synthesis. In general, the reagent is extremely mild, showing only reactivity toward aldehydes, ketones and epoxides. The reagent exhibits a unique reducing applicability in organic synthesis. Thus, the reagent can achieve a clean 1,2-reduction of α,β-unsaturated aldehydes and ketones to produce the corresponding allylic alcohols in 100% purity. In addition, the reagent shows an excellent regioselectivity in the ring-opening reaction of epoxides. Finally, DIBAO3SCH3 shows a high stereo-selectivity in the reduction of cyclic ketones to produce the thermodynamically more stable epimers exclusively.
- Cha, Jin Soon,Noh, Minyeong
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experimental part
p. 840 - 844
(2010/10/21)
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- A simple and highly effective method for hydrogenation of arenes by [Rh(COD)Cl]2
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Hydrogenation of arenes, including chiral BINOLs and the lignin model compounds, has been achieved efficiently by using the simple complex [Rh(COD)Cl]2 as catalyst precursor.
- Wang, Da-Wei,Lu, Sheng-Mei,Zhou, Yong-Gui
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supporting information; experimental part
p. 1282 - 1285
(2009/09/06)
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- Raney Ni-Al alloy-mediated reduction of alkylated phenols in water
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Raney Ni-Al alloy in a dilute aqueous alkaline solution has been shown to be a very powerful reducing agent in the hydrogenation of phenol and alkylated phenols to the corresponding cyclohexanol derivatives.
- Tan, Song-Liang,Liu, Guo-Bin,Gao, Xiang,Thiemann, Thies
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experimental part
p. 5 - 7
(2009/09/06)
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- Rhodium nanoparticles supported on carbon nanofibers as an arene hydrogenation catalyst highly tolerant to a coexisting epoxido group
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Rhodium nanoparticles supported on a carbon nanofiber (Rh/CNF-T) show high catalytic activity toward arene hydrogenation under mild conditions in high turnover numbers without leaching the Rh species; the reaction is highly tolerant to epoxido groups, which often undergo ring-opening hydrogenation with conventional catalysts.
- Motoyama, Yukihiro,Takasaki, Mikihiro,Yoon, Seong-Ho,Mochida, Isao,Nagashima, Hideo
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supporting information; experimental part
p. 5042 - 5045
(2009/12/28)
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- Efficient and Practical Arene Hydrogenation by Heterogeneous Catalysts under Mild Conditions
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An efficient and practical arene hydrogenation procedure based on the use of heterogeneous platinum group catalysts has been developed. Rh/C is the most effective catalyst for the hydrogenation of the aromatic ring, which can be conducted in iPrOH under neutral conditions and at ordinary to medium H 2 pressures (10 atm). A variety of arenes such as alkylbenzenes, benzoic acids, pyridines, furans, are hydrogenated to the corresponding cyclohexyl and heterocyclic compounds in good to excellet yields. The use of Ru/C, less expensive than Rh/C, affords an effective and practical method for the hydrogenation of arenes including phenols. Both catalysts can be reused several times after simple filtration without any significant loss of catalytic activity.
- Maegawa, Tomohiro,Akashi, Akira,Yaguchi, Kiichiro,Iwasaki, Yohei,Shigetsura, Masahiro,Monguchi, Yasunari,Sajiki, Hironao
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experimental part
p. 6953 - 6963
(2010/02/28)
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- Raney ni-al alloy mediated hydrodehalogenation and aromatic ring hydrogenation of halogenated phenols in aqueous medium
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Raney Ni-Al alloy in a dilute aqueous alkaline solution has been shown to be a very powerful reducing agent and is highly effective for the reductive dehalogenation of polyhalogenated phenols and aromatic ring hydrogenation of phenols to the corresponding cyclohexanols.
- Liu, Guo-Bin,Zhao, Hong-Yun,Zhang, Jie,Thiemannb, Thies
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experimental part
p. 342 - 344
(2010/01/16)
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- Transfer hydrogenation of ketones with 2-propanol and Raney nickel
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Raney nickel in refluxing 2-propanol containing a trace of HCl is an effective catalytic system for the reduction of ketones to secondary alcohols. Copyright Taylor & Francis Group, LLC.
- Mebane, Robert C.,Holte, Kimberly L.,Gross, Benjamin H.
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p. 2787 - 2791
(2008/02/12)
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- Reductions of cyclic β-keto esters by individual Saccharomyces cerevisiae dehydrogenases and a chemo-enzymatic route to (1R,2S)-2-methyl-1-cyclohexanol
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Twenty purified dehydrogenases cloned from bakers' yeast (Saccharomyces cerevisiae) and expressed as fusion proteins with glutathione (S)-transferase were tested for their ability to reduce three homologous cyclic β-keto esters. The majority of dehydrogenases reduced ethyl 2-oxo-cyclopentanecarboxylate, yielding a pair of diastereomeric alcohols with consistent (1R)-stereochemistry. Ethyl 2-oxo-cyclohexanecarboxylate reductions afforded only cis-alcohol enantiomers. Ethyl 2-oxo-cycloheptanecarboxylate was accepted by two enzymes in the collection, and both yielded mainly the cis-(1R,2S)-alcohol. Escherichia coli cells overexpressing the YDL124w gene were used in a dynamic kinetic resolution of ethyl 2-oxo-cyclohexanecarboxylate to produce the key intermediate in a chemo-enzymatic synthesis of (1R,2S)-2-methyl-1-cyclohexanol, an important chiral building block.
- Padhi, Santosh Kumar,Kaluzna, Iwona A.,Buisson, Didier,Azerad, Robert,Stewart, Jon D.
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p. 2133 - 2138
(2008/02/11)
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- New active-iron based reducing system for carbonyl compounds and imines. Stereoselective reduction of cyclic ketones
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The reaction of different carbonyl compounds and imines with a mixture of iron(II) chloride tetrahydrate, an excess of lithium powder, and a catalytic amount of 4,4′-di-tert-butylbiphenyl (DTBB, 5 mol%) in THF at room temperature, led to the formation of the corresponding alcohols and amines, respectively. The process was also applied to the transformation of α,β-unsaturated carbonyl compounds into the corresponding saturated alcohols. The new reducing system exhibited good to excellent diastereoselectivity toward the reduction of different monocyclic and polycyclic ketones.
- Moglie, Yanina,Alonso, Francisco,Vitale, Cristian,Yus, Miguel,Radivoy, Gabriel
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p. 2812 - 2819
(2007/10/03)
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- Plants-mediated reduction in the synthesis of homochiral secondary alcohols
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The reduction of 5-hexen-2-one 1, 6-methyl-5-hepten-2-one 2, acetophenone 3, cis-bicyclo[3.2.0]hept-2-en-6-one 4 and 2-methylcyclohexanone 5 with various commercially available plants (i.e., Brassica oleracea botrytis, Cucurbita maxima, Cucurbita pepo, Cynara scolimus, Daucus carota, Foeniculum vulgare and Musa sapientum) is reported. In the reduction of ketones 1-3, both (S)- and (R)-enantiomers 6-8 were obtained in good yields and with appreciable enantiomeric excesses. With racemic ketones 4 and 5, both the diastereomeric endo/exo 9 and 10 and cis/trans 11 and 12 are produced with variable yields and enantiomeric excesses depending on the various plants used.
- Bruni, Renato,Fantin, Giancarlo,Maietti, Silvia,Medici, Alessandro,Pedrini, Paola,Sacchetti, Gianni
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p. 2287 - 2291
(2007/10/03)
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- Rhodium nanoparticles entrapped in boehmite nanofibers: Recyclable catalyst for arene hydrogenation under mild conditions
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A new recyclable rhodium catalyst was synthesized by a simple procedure from readily available reagents, which showed high activities in the hydrogenation of various arenes under 1 atm H2 at room temperature. The Royal Society of Chemistry 2005.
- Park, In Soo,Kwon, Min Serk,Kim, Namdu,Lee, Jae Sung,Kang, Kyung Yeon,Park, Jaiwook
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p. 5667 - 5669
(2007/10/03)
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- Development and comparison of the substrate scope of Pd-catalysts for the aerobic oxidation of alcohols
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(Chemical Equation Presented) Three catalysts for aerobic oxidation of alcohols are discussed and the effectiveness of each is evaluated for allylic, benzylic, aliphatic, and functionalized alcohols. Additionally, chiral nonracemic substrates as well as chemoselective and diastereoselective oxidations are investigated. In this study, the most convenient system for the Pd-catalyzed aerobic oxidation of alcohols is Pd(OAc)2 in combination with triethylamine. This system functions effectively for the majority of alcohols tested and uses mild conditions (3 to 5 mol % of catalyst, room temperature). Pd(IiPr)(OAc)2(H2O) (1) also successfully oxidizes the majority of alcohols evaluated. This system has the advantage of significantly lowering catalyst loadings but requires higher temperatures (0.1 to 1 mol % of catalyst, 60°C). A new catalyst is also disclosed, Pd(IiPr)(OPiv)2 (2). This catalyst operates under very mild conditions (1 mol %, room temperature, and air as the O2 source) but with a more limited substrate scope.
- Schultz, Mitchell J.,Hamilton, Steven S.,Jensen, David R.,Sigman, Matthew S.
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p. 3343 - 3352
(2007/10/03)
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- Surfactant-stabilized aqueous iridium(0) colloidal suspension: An efficient reusable catalyst for hydrogenation of arenes in biphasic media
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Aqueous suspensions of iridium nanoparticles produced by the chemical reduction of IrCl3 assisted by sonication, in the presence of N,N-dimethyl-N-cetyl-N-(2-hydroxyethyl)ammonium chloride salt as surfactant, have shown an efficient activity for the catalytic hydrogenation of various aromatic derivatives in biphasic media under mild conditions. These nanocatalysts can be reused for further runs with a total conservation of activity and provided significant catalytic lifetime for anisole hydrogenation in pure water with 3000 total turnover (TTO).
- Mevellec, Vincent,Roucoux, Alain,Ramirez, Esther,Philippot, Karine,Chaudret, Bruno
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-
- Al-isopropoxydiisobutylalane: A study of the effect of solvent on the rate and stereoselectivity of cyclic ketone reduction
-
The effect of solvent on the rate and stereoselectivity of cyclic ketone reduction by Al-isopropoxydiisobutylalane (DIBAiOPr) has been investigated. In dichloromethane, DIBAiOPr behaves as a bulky reducing agent, approaching the carbonyl group along an equatorial trajectory to produce the axial alcohol with > 10:1 stereoselectivity. In sharp contrast, reduction in toluene gives the complementary outcome, affording the thermodynamically more stable isomer with > 99:1 stereoselectivity.
- Bahia, Perdip S.,Jones, Matthew A.,Snaith, John S.
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p. 9289 - 9291
(2007/10/03)
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- Chemo- and regioselective Meerwein-Ponndorf-Verley and Oppenauer reactions catalyzed by Al-free Zr-zeolite beta
-
Al-free Zr-beta zeolite with Si/Zr up to 75 was synthesized in a fluoride medium. The incorporation of zirconium into zeolite beta induced the formation of increased amounts of polymorph B. Lewis acid sites were predominant in the Al-free Zr-beta. Zr-zeolite beta was an excellent catalyst in the Meerwein-Ponndorf-Verley (MPV) reduction of several alkyl- and aryl-substituted cyclohexanones, with high selectivity to the corresponding alcohols. The catalyst was reusable and no leaching was detected under the reaction conditions. A prominent feature of the Zr-zeolite beta catalyst was its ability to maintain activity even in the presence of rather significant amounts of water, ≤ 9 wt%. The high catalytic ability of Zr-beta zeolites for the MPV reaction was attributed to the presence of Lewis acid sites with appropriate acid strength and to the ease of ligand exchangeability of Zr. Zr-zeolite beta had predominantly Lewis acidity with higher Lewis acid strength than that of Ti- and Sn-zeolite beta, which enabled Zr-zeolite beta to bind the carbonyl group effectively. Regeneration of the catalyst after poisoning by benzoic acid can be effected by thorough washing with 2-propanol. The sample showed good tolerance to the presence of water and pyridine.
- Zhu, Yongzhong,Chuah, Gaikhuan,Jaenicke, Stephan
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-
- Reduction of carbonyl compounds by lanthanide metal/2-propanol: In-situ generation of samarium isopropyloxide for stereoselective Meerwein-Ponndorf- Verley reduction
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The reduction of ketones and aldehydes with lanthanide metals (La, Ce, Sm, Yb) and a catalytic amount of iodine (5 mol %) in iPrOH proceeded smoothly to produce the corresponding alcohols as the major products in good yield, while in THF, methanol, and ethanol the pinacols were mainly produced. The yields of alcohols were improved most effectively by the use of Sm metal, the amount of pinacol produced thus being minimized. The actual reducing agent may be samarium isopropyloxide, which mediates the Meerwein-Ponndorf-Verley-type hydride-transfer reaction, since the reaction can be carried out catalytically with respect to samarium. The stereoselectivities of the reductions of the 2- and 4-substituted cyclohexanones with Sm/iPrOH were higher than those achieved with SmI2/iPrOH or Sm/ H20. The asymmetric reduction of acetophenone could be achieved to give the 1-phenylethanol in up to 95% ee in the presence of the chiral ligand 7. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Fukuzawa, Shin-Ichi,Nakano, Narihito,Saitoh, Takahide
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p. 2863 - 2867
(2007/10/03)
-
- Dod-S-Me and methyl 6-morpholinohexyl sulfide (MMS) as new odorless borane carriers
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Odorless Dod-S-Me (1) and MMS (3) are developed as efficient borane carriers. The yields of hydroborations and reductions with borane complex 2 of 1 are very high and the recovery of 1 after the reaction is quantitative. The borane complexes 4 and 5 of 3 are also useful. In the latter case chromatographic separation is unnecessary when excess oxidizing agent (alkaline H2O2) is used after hydroboration.
- Patra, Pranab K.,Nishide, Kiyoharu,Fuji, Kaoru,Node, Manabu
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p. 1003 - 1006
(2007/10/03)
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- Synthesis of chiral building blocks for use in drug discovery
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In the past decade there has been a significant growth in the sales of pharmaceutical drugs worldwide, but more importantly there has been a dramatic growth in the sales of single enantiomer drugs. The pharmaceutical industry has a rising demand for chiral intermediates and research reagents because of the continuing imperative to improve drug efficacy. This in turn impacts on researchers involved in preclinical discovery work. Besides traditional chiral pool and resolution of racemates as sources of chiral building blocks, many new synthetic methods including a great variety of catalytic reactions have been developed which facilitate the production of complex chiral drug candidates for clinical trials. The most ambitious technique is to synthesise homochiral compounds from non-chiral starting materials using chiral metal catalysts and related chemistry. Examples of the synthesis of chiral building blocks from achiral materials utilizing asymmetric hydrogenation and asymmetric epoxidation are presented.
- Marino, Sharon T.,Stachurska-Buczek, Danuta,Huggins, Daniel A.,Krywult, Beata M.,Sheehan, Craig S.,Nguyen, Thao,Choi, Neil,Parsons, Jack G.,Griffiths, Peter G.,James, Ian W.,Bray, Andrew M.,White, Jonathan M.,Boyce, Rustum S.
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p. 405 - 426
(2007/10/03)
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- Water-resistant solid Lewis acid catalysts: Meerwein-Ponndorf-Verley and Oppenauer reactions catalyzed by tin-beta zeolite
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The catalytic activity of Sn-beta zeolite in the Meerwein-Pondorf-Verley reduction of carbonyl compounds with secondary alcohols as reductants and Oppenauer oxidation of alcohols were performed with quantitative yields to the corresponding product. The catalyst had an excellent activity and selectivity even after four catalytic recycles, and good stereoselectivities to the thermodynamic less favorable cis-alcohol isomer when alkyl-cyclohexanones were used as substrates. A prochiral ketone was reduced within an enantiomeric excess close to 50% when using a chiral alcohol as the reducing reactant. IR studies using cyclohexanone as probe molecule over beta zeolites showed that the more specific Lewis acid sites in the framework of Sn-beta were responsible for its better catalytic activity with respect to Ti- or Al-beta. The order of hydrophobicity of the samples was Ti-beta > Sn-beta > Al-beta. Ti-beta and Sn-beta retained a higher percentage of catalytic activity when water was present in the reaction media. Even with ~ 4 wt % of H2O (0.2 g) in the media, Sn-beta yielded a higher turnover number than Ti- or Al-beta when working in the absence of water.
- Corma, Avelino,Domine, Marcelo E.,Valencia, Susana
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p. 294 - 304
(2007/10/03)
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- Palladium-catalyzed reduction of ketones with nBu2SnH2
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Whereas the Pd(PPh3)4-catalyzed reduction of ketones with nBu3SnH does not proceed at all, the use of nBu2SnH2, instead of nBu3SnH, leads to the efficient reduction of a variety of ketones in the presence of a catalytic amount of Pd(PPh3)4 under mild conditions, providing the corresponding alcohols in good yields. The stereoselectivity in the reduction of cyclic ketones is also investigated by using this Pd(PPh3)4/nBu2SnH2 reduction system.
- Kamiya, Ikuyo,Ogawa, Akiya
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p. 1701 - 1703
(2007/10/03)
-
- Fluorous dimethyl sulfide: A convenient, odorless, recyclable borane carrier
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(matrix presented) Borane gas and 2-(perfluorooctyl)ethyl methyl sulfide form a solid comprised of an approximately 1:1 mixture (fluorous BMS) of sulfide and the corresponding sulfide-borane. Fluorous BMS permits hydroboration of alkenes in a dichloromethane/perfluorinated hydrocarbon mixture with subsequent recycling of the fluorous sulfide by fluorous extraction. The use of fluorous BMS in the asymmetric reduction of ketones catalyzed by a chiral oxaborolidine catalyst, and in the reduction of other functional groups, is also reported.
- Crich, David,Neelamkavil, Santhosh
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p. 4175 - 4177
(2007/10/03)
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- Copper-catalysed aerobic oxidation of alcohols using fluorous biphasic catalysis
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A copper(I) catalysed and TEMPO mediated fluorous biphasic oxidation of primary, secondary, allylic and benzylic alcohols with oxygen in the presence of a bipyridine ligand bearing perfluorinated ponytails is described. High chemoselectivities are observed in the oxidation of substituted cyclohexanols (substituted axial cyclohexanols react 6-8 times faster than the corresponding equatorial cyclohexanols).
- Ragagnin, Gianna,Betzemeier, Bodo,Quici, Silvio,Knochel, Paul
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p. 3985 - 3991
(2007/10/03)
-