- A practical asymmetric conjugate addition to cyclic enones with chiral bifunctional Ru amido catalysts
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A practical asymmetric C-C bond formation to synthetically useful β-chiral cyclic ketones (>99% ee) using bifunctional chiral amido Ru catalysts under an S/C = 1000, the highest ratio achieved so far in the literature for this class of reactions, is descr
- Dub, Pavel A.,Wang, Hui,Watanabe, Masahito,Gridnev, Ilya D.,Ikariya, Takao
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- Phase transfer of enantiopure werner cations into organic solvents: An overlooked family of chiral hydrogen bond donors for enantioselective catalysis
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A study was conducted to investigate phase transfer of ennantiopure Werner cations into organic salts and their use as donors for chiral hydrogen enantioselective catalysis for organic reactions. The study involved developing an extensive aqueous chemistry of these salts and analogues with other diamines. An aqueous solution of a salt derived from racemic trans-1,2-cyclohexanediamine was treated with with a CH2Cl2 solution of NaBAr f. It was observed that the aqueous phase decolorized, while an identical reaction gave an identical (Co(rac-chnx)3)(BAr f)3 in 89% yield as a nonhydrate.
- Ganzmann, Carola,Gladysz, John A.
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- Physico-chemical and Catalytic Properties of Ytterbium introduced into Y-Zeolite
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Ytterbium was introduced into K(+)-exchanged Y-zeolite (Yb/K-Y) by impregnation from a liquid ammonia solution of the metal, and the change in the chemical state of the metal with evacuation temperature was investigated by infrared (IR), X-ray absorbtion fine structure (XAFS) and X-ray photoelectron (XPS) spectroscopies.When ammonia was removed by brief evacuation at room temperature followed by evacuation at 333 K, the IR spectrum showed the presence of Yb amides.The amide species were observed up to 423 K.The Yb L2-edge X-ray absorbtion near-edge structure (XANES) spectrum showed that the Yb species exist as 16.4percent Yb(II) and 83.6percent Yb(III) after evacuation at 333 K.The fraction of Yb(2+) increased with increasing evacuation temperature and reached 44.2percent at 573 K by the decomposition of Yb(II, III) amides to Yb(II, III) imides.The fraction of Yb(III) species increased at an evacuation temperature > 600 K, owing to the decomposition of Yb imides to Yb nitride with concomitant formation of hydrogen.The Yb(II) imide species catalyses the isomerization of but-1-ene and the Michael reaction of cyclopent-2-enone with dimethylmalonate, while the Yb(III) nitride species catalyses the hydrogenation of ethene.
- Baba, Toshihide,Hikita, Satoru,Koide, Ryutaro,Ono, Yoshio,Hanada, Tomoko et al.
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- Lewis acid catalyzed conjugate addition and the formation of heterocycles using Michael acceptors under solvent-free conditions
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Conjugate addition and conjugate-addition-initiated ring closure (CAIRC) reactions of β-dicarbonyl compounds with Michael acceptors have been studied using several Lewis acid catalysts under solvent-free conditions. Excellent chemoselectivity was obtained when various Michael acceptors were treated with several β-dicarbonyl compounds. On the other hand, 2-bromo-2-cyclopentenone and 3-bromo-3-vinyl methyl ketone furnished 2,3-dihydrofurans instead of the 1,4-adducts when treated with the same reagents. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Mekonnen, Alemayehu,Carlson, Rolf
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- Catalytic C-C bond formation promoted by Mg-Al-O-t-Bu hydrotalcite
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Mg-Al-O-t-Bu-hydrotalcite catalyst was found to be an efficient, environmentally attractive and selective solid base catalyst for 1,4 Michael addition. Mg-Al-O-t-Bu hydrotalcite is also effective for simple synthesis of α,β-unsaturated esters and nitriles by condensation of the corresponding activated carboxylic esters or nitriles with various aldehydes by Knoevenagel condensation. These reactions proceeded at room temperature at a greater rate in the presence of Mg-Al-O-t-Bu hydrotalcite than in the presence of any of the other catalysts examined. (C) 2000 Elsevier Science Ltd.
- Choudary,Lakshmi Kantam,Kavita,Venkat Reddy,Figueras
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- Mapping the Surface Groups of Amine-Rich Carbon Dots Enables Covalent Catalysis in Aqueous Media
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Carbon nanodots stand as the missing link between the molecular and the nanoscale world, owing to the unique molecular-like behavior emerging from their synthetic precursors. A converging set of analytical and spectroscopic data yields a precise inventory
- Amato, Francesco,Bonchio, Marcella,Companyó, Xavier,Dell'Amico, Luca,Filippini, Giacomo,Prato, Maurizio,Ragazzon, Giulio,Rosso, Cristian,Vega-Pe?aloza, Alberto
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supporting information
p. 3022 - 3037
(2020/11/03)
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- Bifunctional Ligand-Assisted Catalytic Ketone α-Alkenylation with Internal Alkynes: Controlled Synthesis of Enones and Mechanistic Studies
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Here, we describe a detailed study of the rhodium(I)-catalyzed, bifunctional ligand-assisted ketone α-C-H alkenylation using internal alkynes. Through controlling the reaction conditions, conjugated enamines, α,β- or β,γ-unsaturated ketones, can be selectively accessed. Both aromatic and aliphatic alkynes can be employed as coupling partners. The reaction conditions also tolerate a broad range of functional groups, including carboxylic esters, malonates, secondary amides, thioethers, and free alcohols. In addition, excellent E-selectivity was observed for the tetra-substituted alkene when forming the α,β-unsaturated ketone products. The mechanism of this transformation was explored through control experiments, kinetic monitoring, synthesizing the rhodium-hydride intermediates and their reactions with alkynes, deuterium-labeling experiments, and identification of the resting states of the catalyst.
- Mo, Fanyang,Lim, Hee Nam,Dong, Guangbin
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supporting information
p. 15518 - 15527
(2015/12/26)
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- Concise enantioselective construction of a bridged azatricyclic framework via domino semipinacol-Schmidt reaction
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A TiCl4-promoted domino semipinacol-Schmidt reaction of oxaspiropentane-azide provides an easy access to bridged azatricyclic ring systems, which possess the azaquaternary center, present in the immunosupressant FR901483 and platelet aggregatio
- Puppala, Manohar,Murali, Annamalai,Baskaran, Sundarababu
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supporting information; experimental part
p. 5778 - 5780
(2012/07/14)
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- An efficient organocatalytic method for highly enantioselective michael addition of malonates to enones catalyzed by readily accessible primary amine-thiourea
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A practical and highly enantioselective Michael addition of malonates to enones catalyzed by simple and readily available bifunctional primary amine-thiourea derived from 1,2-diaminocyclohexane is reported. The addition of weak acids and elevated temperature (ca. 50 °C) improved the efficiency of the Michael reaction. This approach enables the efficient synthesis of 1,5-ketoesters with good yields, excellent enantioselectivities (up to 99% ee), and low loading (0.5-5 mol %) of simple chiral primary amine-thiourea catalysts, and is applicable in multigram scale synthesis.
- Dudzinski, Krzysztof,Pakulska, Anna M.,Kwiatkowski, Piotr
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supporting information; experimental part
p. 4222 - 4225
(2012/09/22)
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- HIV Integrase Inhibitors
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The disclosure generally relates to the novel compounds of formula I, including their salts, which inhibit HIV integrase and prevent viral integration into human DNA. This action makes the compounds useful for treating HIV infection and AIDS. The invention also encompasses pharmaceutical compositions and methods for treating those infected with HIV.
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Page/Page column 76
(2009/10/17)
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- Layered double hydroxides-supported diisopropylamide: Synthesis, characterization and application in organic reactions
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The layered double hydroxides-supported diisopropylamide (LDH-DA) catalyst is found to be an efficient and selective solid base for aldol, Knoevenagel, Henry, Michael, transesterification and epoxidation reactions under liquid phase conditions. LDH-DA is synthesized by the interaction of lithium diisopropylamide with LDH-NO3 (as-synthesized) and calcined LDH-NO3. The LDH-DA (Mg/Al, 3/1) and their precursors are well characterized by using various instrumental techniques such as FT-IR, TGA and DTA, powder XRD, solid state 27Al MAS NMR spectroscopy, SEM and XPS (ESCA).
- Kantam, M. Lakshmi,Ravindra,Reddy, Ch. Venkat,Sreedhar,Choudary
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p. 569 - 578
(2007/10/03)
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- 1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD) catalyzed Michael reactions
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1,5,7-Triazabicyclo[4.4.0]dec-5-ene (TBD), a bicyclic guanidine base, has been found to be an excellent catalyst for Michael and Michael-type reactions. A wide variety of Michael donors and acceptors can participate in these reactions using 10-20 mol % of
- Ye, Weiping,Xu, Junye,Tan, Chin-Tong,Tan, Choon-Hong
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p. 6875 - 6878
(2007/10/03)
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- Anodic oxidations of electron-rich olefins: Radical cation based approaches to the synthesis of bridged bicyclic ring skeletons
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The use of intramolecular anodic olefin coupling reactions for building bicyclo[3.2.1]octane ring skeletons has been examined. While simple model systems using bis enol ether substrates readily led to the formation of bicyclic products, application of the reactions to total synthesis efforts were hindered by reactions forming dimethoxy acetal groups at both the terminating and initiating ends of the cyclization reactions. In an effort to solve this problem, ketene acetal based initiating groups have been studied. The use of a ketene dithioacetal group proved especially useful for this purpose.
- Reddy, S.Hari Krishna,Chiba, Kazuhiro,Sun, Yongmao,Moeller, Kevin D
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p. 5183 - 5197
(2007/10/03)
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- Reaction of Dicarbomethoxycarbene with Acetaldehyde and Simple Ketones
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Singlet dicarbomethoxycarbene reacts with acetaldehyde to give dioxolane 8, the ultimate product of formation of ylide 10 and subsequent addition of a second molecule of aldehyde.Photosensitized generation of the carbene gives increased hydrogen abstraction and decreased products derived from the ylide.Replacement of the aldehyde with a ketone changes the course of the reaction and dioxolanes (11, 20, and 26) become the major products.Suggestions are made for the mechanisms of the singlet and triplet reactions and for the peculiar behavior of acetone in which generation of singlet and triplet carbene gives the same product slate.
- L'Esperance, Robert P.,Ford, Thomas M.,Jones, Maitland
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p. 209 - 213
(2007/10/02)
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