- A NEW AND SIMPLE SYNTHESIS OF ALKOXY- AND ARYLOXYMETHYLLITHIUM REAGENTS (ROCH2Li)
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A series of halomethyl alkyl and aryl ethers can be converted to the corresponding organolithium reagents (ROCH2Li) in a one-flask operation by sequential treatment (1) with stannous chloride-lithium bromide complex in tetrahydrofuran (THF) and (2) with n-butyllithium.
- Corey, E. J.,Eckrich, Thomas M.
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Read Online
- Tandem Acid/Pd-Catalyzed Reductive Rearrangement of Glycol Derivatives
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Herein, we describe the acid/Pd-tandem-catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen-based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a PdII or Pd0 precursor in loadings as low as 0.75 mol % and α,α′-bis(di-tert-butylphosphino)-o-xylene as ligand. The reduction step makes use of formic acid as an easy-to-handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.
- Ciszek, Benjamin,Fleischer, Ivana,Kathe, Prasad,Schmidt, Tanno A.
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supporting information
p. 3641 - 3646
(2020/03/25)
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- Enantiopure encaged Verkade's superbases: Synthesis, chiroptical properties, and use as chiral derivatizing agent
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Verkade's superbases, entrapped in the cavity of enantiopure hemicryptophane cages, have been synthesized with enantiomeric excess (ee) superior to 98%. Their absolute configuration has been determined by using electronic circular dichroism (ECD) spectros
- Yang, Jian,Chatelet, Bastien,Hérault, Damien,Dufaud, Véronique,Robert, Vincent,Grass, Stéphane,Lacour, Jér?me,Vanthuyne, Nicolas,Jean, Marion,Albalat, Muriel,Dutasta, Jean-Pierre,Martinez, Alexandre
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p. 139 - 146
(2019/12/27)
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- PYRIDAZINONES AND METHODS OF USE THEREOF
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Disclosed are compounds according to Formula (A), and related tautomers and pharmaceutical compositions. Also disclosed are therapeutic methods, e.g., of treating kidney diseases, using the compounds of Formula (A).
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Page/Page column 261; 262
(2019/04/11)
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- Ru(III) complex anchored onto amino-functionalized MIL-101(Cr) framework via post-synthetic modification: an efficient heterogeneous catalyst for ring opening of epoxides
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In this work, the metallo Schiff base-functionalized metal–organic framework was prepared by post-synthetic method and used as an electron-deficient catalyst for the alcoholysis of epoxides. In this manner, the aminated MIL-101 was modified with 2-pyridine carboxaldehyde and then the prepared Schiff base reacted with RuCl3. This new catalyst, MIL-101–NH2–PC–Ru, was characterized by Fourier transform infrared, UV–Vis spectroscopic techniques, X-ray diffraction, BET, inductively coupled plasma atomic emission spectroscopy and field-emission scanning electron microscopy. In the presence of this heterogeneous catalyst, ring opening of epoxides was performed under mild condition to show the significant ability and successful applications of Lewis acid containing catalysts in corporation with metal–organic frameworks. The reusability of the catalyst was also investigated. No noticeable decrease in the catalytic activity was found after four consecutive times.
- Jafari, Aneseh Khalatbari,Kardanpour, Reihaneh,Tangestaninejad, Shahram,Mirkhani, Valiollah,Moghadam, Majid,Mohammadpoor-Baltork, Iraj,Zadehahmadi, Farnaz
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p. 997 - 1006
(2018/05/23)
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- Aerobic Photooxidative Synthesis of β-Alkoxy Monohydroperoxides Using an Organo Photoredox Catalyst Controlled by a Base
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Transition-metal-free synthesis of β-alkoxy monohydroperoxides via aerobic photooxidation using an acridinium photocatalyst was developed. This method enables the synthesis of some novel hydroperoxides. The peroxide source is molecular oxygen, which is cost-effective and atomically efficient. Magnesium oxide plays an important role as a base in the catalytic system.
- Asano, Yuya,Nagasawa, Yoshitomo,Yamaguchi, Eiji,Itoh, Akichika
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p. 409 - 412
(2018/02/21)
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- Microporous Nanotubes and Nanospheres with Iron-Catechol Sites: Efficient Lewis Acid Catalyst and Support for Ag Nanoparticles in CO2 Fixation Reaction
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FeIII-containing hyper-crosslinked microporous nanotubes (FeNTs) and nanospheres (FeNSs) are synthesized through the reaction of catechol and dimethoxymethane in the presence of FeCl3 or CF3SO3H. Both FeNTs and FeNSs demonstrate excellent catalytic activity in Lewis acid catalysis (hydrolysis and regioselective methanolysis of styrene oxide) and tandem catalysis involving a sequential oxidation-cyclization process, which selectively converts benzyl alcohol to 2-phenyl benzimidazole. Apart from Lewis acidity, the FeNTs and FeNSs also showed CO2 uptake capacities of 2.6 and 2.2 mmol g?1, respectively, at a pressure of 1 atm and temperature of 273 K. Furthermore, Ag nanoparticles are immobilized successfully on the surfaces of FeNTs and FeNSs by the liquid-phase impregnation method to prepare Ag@FeNT and Ag@FeNS nanocomposites, which show high catalytic activity for the selective fixation of CO2 to phenylacetylene to yield phenylpropiolic acid at 60 °C and 1 atm CO2 pressure. Hence, FeIII-catechol-containing hyper-crosslinked nanotubes and nanospheres have huge potential not only as Lewis acid catalysts, but also as excellent supports for immobilizing Ag nanoparticles in the design of a robust catalyst for the carboxylation of terminal alkynes, which has wide scope in catalysis and environmental research.
- Modak, Arindam,Bhanja, Piyali,Bhaumik, Asim
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p. 14189 - 14197
(2018/09/11)
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- Scalable and super-stable exfoliation of graphitic carbon nitride in biomass-derived γ-valerolactone: Enhanced catalytic activity for the alcoholysis and cycloaddition of epoxides with CO2
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Biomass-derived γ-valerolactone (GVL) could exfoliate bulk g-C3N4 to form a super-stable dispersion of few-layer g-C3N4 nanosheets with a high concentration of up to 0.8 mg mL-1 due to the polarity and the appropriate surface energy of GVL. The exfoliation process can be easily extended to a 200 ml scale and should be extended further. The formed g-C3N4 nanosheets showed enhanced activity for the alcoholysis of epoxides and the cycloaddition of epoxides with CO2 owing to their higher specific surface areas and more exposed active centers than the bulk g-C3N4. This affords a green, facile and scalable method to form few-layer g-C3N4 nanosheets and further expand the application of g-C3N4 materials to the field of non-photocatalysis.
- Xue, Zhimin,Liu, Feijie,Jiang, Jingyun,Wang, Jinfang,Mu, Tiancheng
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p. 5041 - 5045
(2017/11/09)
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- Modular bisphosphine ligands: Preparation and application in enantioselective catalytic reactions
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A set of six chiral modular C2-symmetric bisphosphine ligands have been synthesized in a straightforward manner through a two-step reaction from the corresponding diols with moderate yields. The applicability of these chiral ligands was evaluated in ruthenium(II)-catalyzed transfer hydrogenation reactions (up to >99% conversion) and palladium(0)-catalyzed enantioselective allylic substitution reactions (up to 70% chemical yield and 43% ee).
- G?k, Ya?ar,Karayi?it, ?lker ümit,G?k, Halil Zeki
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- An Fe3O4 nanoparticle-supported Mn (II)-azo Schiff complex acts as a heterogeneous catalyst in alcoholysis of epoxides
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In this paper, an azo-containing Schiff base complex of manganese [Mn2+-azo ligand@APTES-SiO2@Fe3O4] immobilized on chemically modified Fe3O4 nanoparticles has been used as a magnetically retrievable catalyst for the alcoholysis of different epoxides to their corresponding alkoxy alcohols with methanol, ethanol and n-propanol. The newly magnetic nanoparticles (MNPs) were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and vibrating sample magnetometry (VSM).
- Olia, Fahimeh Karami,Sayyahi, Soheil,Taheri, Narges
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p. 370 - 376
(2017/03/15)
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- Well-defined epoxide-containing styrenic polymers and their functionalization with alcohols
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Polymers containing electrophilic moieties, such as activated esters, epoxides, and alkyl halides, can be readily modified with a variety of nucleophiles to produce useful functional materials. The modification of epoxide-containing polymers with amines and other strong nucleophiles is well-documented, but there are no reports on the modification of such polymers with alcohols. Using phenyloxirane and glycidyl butyrate as low molecular weight model compounds, it was determined that the acid-catalyzed ring-opening of aryl-substituted epoxides by alcohols to form β-hydroxy ether products was significantly more efficient than that of alkyl-substituted epoxides. An aryl epoxide-type styrenic monomer, 4-vinylphenyloxirane (4VPO), was synthesized in high yield using an improved procedure and then polymerized in a controlled manner under reversible addition-fragmentation chain-transfer (RAFT) polymerization conditions. A successful chain extension with styrene proved the high degree of chain-end functionalization of the poly4VPO-based macro chain transfer agent. Poly4VPO was modified with a library of alcohols and phenols, some of which contained reactive functionalities, e.g., azide, alkyne, allyl, etc., using either CBr4 (in PhCN at 90°C for 2-3 days) or BF3 (in CH2Cl2 at ambient temperature over 30 min) as the catalyst. The resulting β-hydroxy ether-functionalized homopolymers were characterized using size exclusion chromatography, 1H NMR and IR spectroscopy, and thermal gravimetric analysis.
- McLeod, David C.,Tsarevsky, Nicolay V.
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p. 1132 - 1144
(2016/03/12)
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- A highly efficient protocol for regioselective ring-opening of epoxides with alcohols, water, acetic acid, and acetic anhydride catalyzed by SbF3
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SbF3as an efficient catalyst has been used for regioselective alcoholysis, acetolysis and hydrolysis of epoxides to the corresponding β-alkoxy, β-acetoxy alcohols, and 1,2-diols in high to excellent yields. This study also represents a convenient synthesis of vic-diacetates from ring-opening of epoxides with acetic anhydride.
- Zeynizadeh, Behzad,Gilanizadeh, Masumeh,Aminzadeh, Farkhondeh Mohammad
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p. 1051 - 1056
(2016/07/06)
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- Steric vs. electronic effects in the Lactobacillus brevis ADH-catalyzed bioreduction of ketones
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Lactobacillus brevis ADH (LBADH) is an alcohol dehydrogenase that is commonly employed to reduce alkyl or aryl ketones usually bearing a methyl, an ethyl or a chloromethyl as a small ketone substituent to the corresponding (R)-alcohols. Herein we have tested a series of 24 acetophenone derivatives differing in their size and electronic properties for their reduction employing LBADH. After plotting the relative activity against the measured substrate volumes we observed that apart from the substrate size other effects must be responsible for the activity obtained. Compared to acetophenone (100% relative activity), other small substrates such as propiophenone, α,α, α-trifluoroacetophenone, α-hydroxyacetophenone, and benzoylacetonitrile had relative activities lower than 30%, while medium-sized ketones such as α-bromo-, α,α-dichloro-, and α,α-dibromoacetophenone presented relative activities between 70% and 550%. Moreover, the comparison between the enzymatic activity and the obtained final conversions using an excess or just 2.5 equiv. of the hydrogen donor 2-propanol, denoted again deviations between them. These data supported that these hydrogen transfer (HT) transformations are mainly thermodynamically controlled. For instance, bulky α-halogenated derivatives could be quantitatively reduced by LBADH even employing 2.5 equiv. of 2-propanol independently of their kinetic values. Finally, we found good correlations between the IR absorption band of the carbonyl groups and the degrees of conversion obtained in these HT processes, making this simple method a convenient tool to predict the success of these transformations. The Royal Society of Chemistry.
- Rodriguez, Cristina,Borzecka, Wioleta,Sattler, Johann H.,Kroutil, Wolfgang,Lavandera, Ivan,Gotor, Vicente
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supporting information
p. 673 - 681
(2014/01/06)
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- Grafted chromium 13-membered dioxo-macrocyclic complex into aminopropyl-based nanoporous SBA-15
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In a new approach, chromium (III) tetraaza dioxo ligand was grafted onto functionalized SBA-15 after four step reactions by using coordinating ability of anchored amino functionalized SBA-15. After the termination of each step, the obtained product was characterized by FT-IR, low-angle X-ray diffraction (LA-XRD), N2 adsorption-desorption isotherms (Brunauer-Emmett-Teller (BET)-Barret-Joyner-Halenda (BJH)) and thermogravimetric analysis (TGA), and used as catalyst for the efficient and regioselective alcoholysis of styrene oxide to 2-alkoxy-1-phenylethanol product at ambient temperature.
- Tarlani, Aliakbar,Joharian, Vmonika,Narimani, Khashayar,Muzart, Jacques,Fallah, Mahtab
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p. 255 - 259
(2013/07/26)
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- COMPOSITIONS AND METHODS FOR MODULATING LPA RECEPTORS
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The present invention relates to compounds of Formula (1), or pharmaceutically acceptable salts thereof and their pharmaceutical compositions, wherein variables are as defined herein, which are useful as modulators of the activity of lysophosphatidic acid (LPA).
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Page/Page column 88-89
(2012/10/18)
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- HYDROGENATION OF ESTERS OR CARBONYL GROUPS WITH PHOSPHINO-OXIDE BASED RUTHENIUM COMPLEXES
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The present invention relates to the field of catalytic hydrogenation and, more particularly, to the use of specific ruthenium catalysts or pre-catalysts in hydrogenation processes for the reduction of ketones, aldehydes, esters or lactones into their corresponding alcohols or diols respectively. The preferred catalysts are ruthenium complexes comprising a ligand of the type (N—N) type and a ligand of the type (P—PO).
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Page/Page column 15; 16
(2011/08/08)
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- Quaternary ammonium ionic liquids as Bi-functional catalysts for one-step synthesis of dimethyl carbonate from ethylene oxide, carbon dioxide and methanol
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One kind of novel ionic liquids (ILs) with a tertiary amino moiety and a quaternary ammonium group were synthesized and identified by FT-IR, 1H and 13C NMR. The elemental chemical state and basicity of ILs were determined by XPS and Hammett indicator method, respectively. Then the catalytic performance of these bi-functional catalysts was investigated in one-step synthesis of dimethyl carbonate (DMC) from ethylene oxide (EO), carbon dioxide and methanol. The best catalytic performance with 99% EO conversion and a maximum of 74% DMC selectivity was obtained using [N111,6N11]I as catalyst under optimized reaction conditions. And the catalyst could be reused for several times. Normally, stronger basicity could be obtained by altering the anions with different nucleophilicity in ILs and a better catalytic activity could be achieved correspondingly. A mechanism that both the ring opening of epoxide through nucleophilic attacks and the transesterification play an important role in the reaction was proposed based on experimental results.
- Li, Jian,Wang, Liguo,Shi, Feng,Liu, Shimin,He, Yude,Lu, Liujin,Ma, Xiangyuan,Deng, Youquan
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experimental part
p. 339 - 346
(2011/12/22)
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- The tetramethylguanidine-based ionic liquid-catalyzed synthesis of propylene glycol methyl ether
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Tetramethylguanidine-based ionic liquids were used as effective catalysts for the synthesis of propylene glycol methyl ether from methanol and propylene oxide. 1-Methoxy-2-propanol was produced in nearly 90% yield under much milder conditions. The catalyst can be reused at least ten times without any considerable decrease in its activity and selectivity.
- Liang, Shuguang,Liu, Huizhen,Zhou, Yinxi,Jiang, Tao,Han, Buxing
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supporting information; scheme or table
p. 2534 - 2536
(2011/01/12)
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- Biomimetic transfer hydrogenation of 2-alkoxy- and 2-aryloxyketones with iron-porphyrin catalysts
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In situ generated iron porphyrins are applied as homogeneous catalysts in the transfer hydrogenation of α-substituted ketones. Using 2-propanol as hydrogen donor various protected 1,2-hydroxyketones are reduced to the corresponding mono-substituted 1,2-di
- Enthaler, Stephan,Spilker, Bj?rn,Erre, Giulia,Junge, Kathrin,Tse, Man Kin,Beller, Matthias
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p. 3867 - 3876
(2008/09/20)
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- Chiral C2-boron-bis(oxazolines) in asymmetric catalysis - A theoretical study of the catalyzed enantioselective reduction of ketones promoted by catecholborane
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C2-Symmetrical boron complexes, prepared by the reactions of 2,2′-methylenebis(oxazolines) (BOXs) with catecholborane (CATBH), can be used as catalysts (5-10 mol-%) in the enantioselective reduction of prochiral ketones (ee 72-86 %), giving the desired alcohols in satisfactory yields. We have theoretically investigated the mechanism of the reduction of chloroacetophenone at the DFT level and the computational results have provided a complete mechanistic picture, which explains the stereochemical outcome of the reaction. The B-BOXate complex binds both the reducing agent CATBH and the carbonyl compound, activating the former as a hydride donor and enhancing the electrophilicity of the latter. Moreover, the structure of two boron-BOX (BOXate) complexes has been confirmed by means of X-ray diffraction techniques. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Bandini, Marco,Bottoni, Andrea,Cozzi, Pier Giorgio,Miscione, Gian Pietro,Monari, Magda,Pierciaccante, Rossana,Umani-Ronchi, Achille
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p. 4596 - 4608
(2007/10/03)
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- Process for preparation of 2-phenyl ethanol
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The present invention provides an improved process for preparation of 2-phenyl ethanol. More specifically, the present invention relates to a process for preparing 2-phenyl ethanol by catalytic transfer hydrogenation of styrene oxide, in the presence of a supported transition metal catalyst. The catalyst system comprises of a palladium supported on silica, alumina, clay or charcoal.
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Page/Page column 4
(2008/06/13)
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- PROCESS FOR PREPARATION OF 2-PHENYL ETHANOL
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The present invention provides an improved process for preparation of 2-phenyl ethanol. More specifically, the present invention relates to a process for preparing of 2-phenyl ethanol by catalytic transfer hydrogenation of styrene oxide, in the presence of a supported transition metal catalyst. The catalyst system comprises of a palladium supported on silica, alumina, clay or charcoal.
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Page/Page column 8
(2008/06/13)
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- The role of organic fluorine in directing alkylation reactions via lithium chelation
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The fluorine of a fluoromethyl group displays a measurable chelation effect to lithium during α-methylation of an ester with lithium diisopropylamide (LDA) and methyl iodide. A series of esters is compared with F, H and O, and the resultant diastereoselectivity is consistent with the intermediate capacity of F to chelate lithium relative to H and O. In a second system which involved comparing a tertiary organic fluorine with hydrogen, no such effect is apparent, most probably due to adverse steric effects. The absolute and relative stereochemistry of the predominant diastereoisomers are confirmed by X-ray crystallography of suitable crystalline derivatives in each case. It is concluded that there is a potential role for organic-bound fluorine to become involved in lithium chelation in well-designed enolate alkylation systems. The diastereoselectivity of alkylation is explored comparing the coordination ability of H, F and OR substituents in the above model.
- Tenza, Kenny,Northen, Julian S.,O'Hagan, David,Slawin, Alexandra M.Z.
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p. 1779 - 1790
(2007/10/03)
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- Carbodiimide-Promoted Olefin Epoxidation with Aqueous Hydrogen Peroxide
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Commercially available carbodiimides in hydroxylic solvents containing hydrogen peroxide with mildly basic or acidic catalysts have been found to promote the epoxidation of olefins. A commercially available 30% aqueous solution of hydrogen peroxide serves as the oxidant for this process. The presumed reactive species is a peroxyisourea generated in situ by the addition of hydrogen peroxide to the carbodiimide.
- Majetich, George,Hicks, Rodgers,Sun, Guang-Ri,McGill, Patrick
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p. 2564 - 2573
(2007/10/03)
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- EFFICIENT AND/OR SELECTIVE METHYLATION BY DIAZOMETHANE OF ALCOHOLS, HALO ALCOHOLS, GLYCOLS, AMINO ALCOHOLS AND MERCAPTO ALCOHOLS WITH THE USE OF A PROTON-EXCHANGED X-TYPE ZEOLITE AS AN ACID-BASE BIFUNCTIONAL CATALYST
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Reactions of diazomethane with butanol, allyl alcohol and β- and γ-halo alcohols led to efficient methylation (giving the corresponding methyl ethers) with the use of a proton-excahnged X-type zeolite compared with H2SO4.The reactions with propylene and isobutylene glycols using the zeolite provided regioselective methylation of the primary OH rather than the secondary or tertiary OH, whereas regioselectivity was not observed in the reactions using H2SO4.The reactions with 2-aminoethanol and 2-mercaptoethanol showed high chemoselective S-methylation and N-monomethylation, respectively, in the presence of the zeolite instead of H2SO4.The mechanism for the reactions is proposed to involve acid-base bifunctional catalysis of the zeolite in which the acidic site reacts with diazomethane to form its conjugate acid, and the nucleophilicity of OH and SH groups is enhanced by the interaction of the basic site with the proton of the groups.
- Takeuchi, Hiroshi,Kishioka, Hiroaki,Kitajima, Kunio
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p. 121 - 126
(2007/10/02)
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- Baker's yeast-mediated reduction of α-hydroxy ketones and derivatives: The steric course of the biotransformation
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The results from the baker's yeast-mediated reduction of the acetates 3a- d and the methyl ethers 5a-d were compared with the same biotransformation which converts the α-hydroxy ketones 1a-d into the (R)-diols 2a-d (90- 98%ee); the acetates 3a-d afford the (S)-monoacetates 4a-d (72-94% ee) and the methyl ethers 5a-d are reduced to the (R)-monoethers 6a-d (64-76% ee).
- Ferraboschi, Patrizia,Grisenti, Paride,Manzocchi, Ada,Santaniello, Enzo
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p. 10539 - 10548
(2007/10/02)
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- Effects of Para-Substituents on the Mechanisms of Solvolysis of Styrene Oxides
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Rate and product studies of the hydronium ion-catalyzed, hydroxide ion-catalyzed, and spontaneous reactions of styrene oxide and its p-CH3O, p-CH3, p-Cl, and p-O2N-derivatives in water solutions have been carried out.A Hammett correlation of log k for the acid-catalyzed reactions vs ?+ gives a slope ρ+ of -4.2 and only diol products are formed.An intermediate in the hydronium ion-catalyzed hydrolysis of p-methoxystyrene oxide is trapped, subsequent to its rate-limiting formation, by azide ion.The spontaneous reactions of p-methylstyrene oxide and styrene oxide yield only diol products, and their reactions in 18O-water indicate that >/= 98percent and ca. 95percent, respectively, of 18O is incorporated into the benzyl positions.Nucleophilic addition of water to the benzyl carbon of neutral epoxide is proposed as the mechanism of the primary component of the spontaneous reaction for the p-CH3-, p-H- and p-Cl-substrates on the basis of a Hammett ρ of -2.0.The spontaneous rate constant for reaction of p-methoxystyrene oxide is much greater than that expected from a Hammett correlation for the p-CH3, p-H-, and p-Cl-styrene oxides.This increased rate is attributed to the incursion of a reaction that yields mainly (>80percent) p-methoxyphenylacetaldehyde.The regiochemistries of addition of hydroxide ion in 18O-water to p-CH3-, p-H-, and p-Cl-, and p-O2N-substituted styrene oxides were also determined and found to vary as functions of the para substituent.Addition of hydroxide and methoxide ions to the α-carbon is favored by electron-donating groups in the phenyl ring, and addition of these nucleophiles to the β-carbon is favored by electron-withdrawing groups in the phenyl ring.
- Blumenstein, Jeffrey J.,Ukachukwu, Victoria C.,Mohan, Ram S.,Whalen, Dale L.
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p. 924 - 932
(2007/10/02)
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- Chiral sulfur-reagents for the preparation of optically active epoxides
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Acyclic chiral sulfides which could be easily synthesized in both enantiomeric forms leading to poor yields and/or to racemic epoxides, Eliel's oxathiane reagent was used and proved to provide chiral trans diarylepoxides in high yield (70-80%) and enantiomeric purities up to 70-100%, with no rearrangement problems. It was also found that phase-transfer conditions were the easiest and the most efficient for these reactions.
- Solladie-Cavallo,Adib
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p. 2453 - 2464
(2007/10/02)
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- Process for asymmetrically reducing carbonyl compounds
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There is disclosed a process for asymmetrically reducing a carbonyl compound, which comprises reducing the carbonyl compound by the use of a reducing agent comprising (i) an optically active tartaric acid or ester thereof and (ii) a metal borohydride, thereby producing an optically active hydroxyl compound. The process can be used for the production of optically active hydroxyesters and alcohols from ketoesters and ketones. These products are useful for the production of medicaments and liquid crystals.
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- Organotin Phosphate Condensates as a Catalyst of Selective Ring-Opening of Oxiranes by Alcohols
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The highly regioselective alcoholysis of oxiranes is catalyzed by organotin phosphate condensates, providing a variety of β-alkoxy alcohols in good yields.The selectivity of the nucleophilic attack is dependent on the structures of epoxides.The gem-dialkyloxiranes are cleaved on the tertiary carbon, while β,γ-epoxy alcohols and their derivatives gave C-3 attack products.The anti stereoisomers are solely produced in the latter case.Thus the catalysis is both acidic and coordinative.Of practical importance is the recycled use of the catalyst without any appreciable decrease in the activity and the selectivities.
- Otera, Junzo,Niibo, Yoshihisa,Tatsumi, Naofumi,Nozaki, Hitosi
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p. 275 - 278
(2007/10/02)
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- MODEL REACTIONS FOR THE STUDY OF HYDROGENATION AND ACIDIC ACTIVITY OF PALLADIUM CATALYSTS
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Palladium catalysts have been used to study the hydrogenation of 1-phenyl-2-butene-1-ol which is accompanied by several side reactions considered to be acid-catalysed.Another model reaction studied was dehydration and subsequent hydrogenation or hydrogenolysis of 1-phenyl-1,3-propanediol to 3-phenyl-1-propanol, accompanied by formation of propylbenzene.The dehydration and propylbenzene formation can be again classified as acid-catalysed reactions.Another one is methanolysis of styrene oxide taking place under conditions of liquid phase hydrogenation due to the acid properties of Pd-H systems.Hydrogenation activity of Pd catalysts was tested by hydrogenation of cyclohexene.Sixteen Pd catalysts on different supports and with different content of active component were used, their activity and selectivity was determined and the effect of variable parameters in the synthesis of these catalysts on the activity and selectivity is discussed.
- Cerveny, Libor,Du, Nguyen Thi,Paseka, Ivo
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p. 2019 - 2027
(2007/10/02)
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- Alcoxymethyltributyletains precurseurs d'alcoxymethyllithiums: application a la synthese de monoethers d'α-glycols et a l'homologation de cetones en aldehydes
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Ethoxymethyltributyltin (obtained from diethoxymethyltributyltin, acetyl chloride and tributyltin hydride) and methoxymethyltributyltin (obtained from chloromethyl-methyl ether and tributylstannylmagnesium chloride) have been transmetallated with butyllithium to give the corresponding alkoxymethyl lithium reagents.This reaction, although usually performed in ether, is possible in a variety of other solvents thus simplifying some of the problems encountered during isolation of the products.The alkoxymethyllithiums obtained react with aldehydes and ketones to give cleanly the corresponding monoprotected α-glycols.Stereochemical trends were observed for hydratropaldehyde and 4-tertiarybutylcyclohexanone, while regiochemical trends were evaluated in the case of cyclohexen-2-one.Syntheis of aldehydes has been achieved in good yields from tertiary monoprotected α-glycols using conventional methods.
- Duchene, Alain,Mouko-Mpegna, David,Quintard, Jean-Paul
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p. 787 - 793
(2007/10/02)
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- HIGHLY REGIOSELECTIVE RING OPENING OF EPOXIDES WITH ALCOHOLS CATALYZED BY ORGANOTIN PHOSPHATE CONDENSATES
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Organotin phosphate condensates proved to catalyze the ring opening reaction of epoxides with alcohols in a highly regioselective manner.
- Otera, Junzo,Yoshinaga, Yukari,Hirakawa, Kazuhisa,Nakata, Tetsuya
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p. 3219 - 3222
(2007/10/02)
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- FACILE HYDROGEN/METAL EXCHANGE BETWEEN BUTYLPOTASSIUM AND SATURATED ETHERS
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At temperature between -100 and -40 deg C, lithium salt-free butylpotassium (prepared from dibutylmercury) readily metalates saturated ethers such as dimethyl ether or tetrahydrofuran.
- Lehmann, Ruth,Schlosser, Manfred
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p. 745 - 748
(2007/10/02)
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