- Coupling Reaction between Aldehydes and Non-Activated Hydrocarbons via the Reductive Radical-Polar Crossover Pathway
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Herein, we describe the generation of an organochromium-type carbanion species from a non-activated C-H bond and its nucleophilic addition to aldehydes. The catalytic carbanion generation occurred through formal deprotonation of a non-activated C-H bond under mild conditions and did not need the prefunctionalization or anion stabilizing group. Carbon radical intermediates generated by decatungstate photocatalyst-mediated hydrogen abstraction were captured by a chromium salt with the reductive radical-polar crossover reaction to produce organochromium carbanions.
- Yahata, Kenzo,Sakurai, Shu,Hori, Shuhei,Yoshioka, Shin,Kaneko, Yuki,Hasegawa, Kai,Akai, Shuji
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supporting information
p. 1199 - 1203
(2020/02/04)
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- Influence of Hydrogen Bond Donating Sites in UiO-66 Metal-Organic Framework for Highly Regioselective Methanolysis of Epoxides
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A Zr(IV)-based UiO-66 metal-organic framework (MOF) (named 1) was synthesized by employing 1-(aminomethyl)naphthalene-2-ol appended terephthalate linker and Zr(IV) salt via solvothermal method and subsequently characterized. Furthermore, the potential efficiency of activated (named 1′) form of as-synthesized MOF was investigated as an organocatalyst for the ring-opening of epoxide by methanol. The catalytic performance of 1 and 1′ was studied in the methanolysis of styrene oxide as a model substrate and the activity of 1′ was also examined with various alcohols. Under the optimized reaction conditions, the catalytic performance of 1′ reached 96 % conversion of styrene oxide to its corresponding product with 98 % regioselectivity. The reusability and stability of the catalyst were proved by recycling up to four runs in the methanolysis of styrene oxide. The Lewis acidity originating from metal nodes and hydrogen bond donating (HBD) sites in the linker is distributed homogeneously throughout the framework, thus playing crucial role in the activation of epoxide with easy accessibility.
- Anbu, Nagaraj,Biswas, Shyam,Das, Aniruddha,Dhakshinamoorthy, Amarajothi,Sk, Mostakim
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- Zirconium triflate grafted on SBA-15 as a highly efficient solid acid catalyst for ring opening of epoxides by amines and alcohols
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Metal (Al, Ti, Zr) triflate grafted mesoporous SBA-15 (AlTf/S, TiTf/S, ZrTf/S) samples were synthesized as inexpensive solid acid materials by a simple one-pot-two-step synthesis methodology. These materials were characterized by X-ray diffraction, N2-sorption, thermogravimetric analysis, Fourier transform infrared spectroscopy (FT-IR), in-situ pyridine FT-IR spectroscopy, and elemental analysis. ZrTf/S was found to be a highly efficient and reusable solid acid catalyst for ring opening of epoxides with amines and alcohols and produced β-amino alcohols and β-alkoxy alcohols respectively under ambient reaction conditions. The ZrTf/S catalyst showed the highest activity, which was attributed to its high acidity compared with that of the Ti and Al containing samples.
- Tayade, Kamlesh N.,Wang, Lianyue,Shang, Sensen,Dai, Wen,Mishra, Manish,Gao, Shuang
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p. 758 - 766
(2017/04/24)
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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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- An environmentally benign catalytic method for efficient and selective nucleophilic ring opening of oxiranes by zirconium tetrakis(dodecyl Sulfate)
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An operationally simple and environmentally benign protocol for a highly regio- and chemoselective preparation of β-substituted alcohols by means of ring-opening reactions of oxiranes with various aliphatic alcohols, H 2O, NaN3 , and NaCN as nucleophiles in the presence of catalytic amounts of zirconium tetrakis(dodecyl sulfate) as Lewis acid/surfactant-combined catalysts (LASCs) was developed. The high efficiency of the catalyst was confirmed by the high product yields obtained within desired times and, in particularly by the reusability of the ZrIV complex.
- Jafarpour, Maasoumeh,Rezaeifard, Abdolreza,Aliabadi, Marzieh
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scheme or table
p. 405 - 413
(2010/05/19)
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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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- 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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- t-BUTOXYMETHYLLITHIUM: DIRECT PREPARATION FOM t-BUTYL METHYL ETHER AND APPLICATIONS AS A HYDROXYMETHYL ANION EQUIVALENT
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t-Butyl methyl ether can be metallated directly to afford a reactive and synthetically useful hydroxymethyl anion equivalent.
- Corey, E. J.,Eckrich, Thomas M.
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p. 3165 - 3168
(2007/10/02)
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- 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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p. 3163 - 3164
(2007/10/02)
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- EFFICIENT CATALYSIS OF HETEROPOLY ACID FOR ALCOHOLYSIS OF EPOXIDE
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Heteropoly acid (HPA) was found to catalyze the alcoholysis of epoxide more efficiently than the conventional acid catalysts such as sulfuric acid, perchloric acid and p-toluenesulfonic acid, at 45 deg C in the homogeneous liquid phase.The reason for the high catalytic activity of HPA is also discussed.
- Izumi, Yusuke,Hayashi, Kyoji
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p. 787 - 790
(2007/10/02)
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