- Highly Efficient Oxidation of Secondary Alcohols to Ketones Catalyzed by Manganese Complexes of N4 Ligands with H2O2
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The manganese complex Mn(S-PMB)(CF3SO3)2 was proven to be highly efficient in the catalytic oxidation of several benzylic and aliphatic secondary alcohols with H2O2 as the oxidant and acetic acid as the additive. A maximum turnover number of 4700 was achieved in the alcohol oxidation. In addition, the Hammett analysis unveiled the electrophilic nature of this manganese catalyst with N4 ligand. (Chemical Equation Presented).
- Shen, Duyi,Miao, Chengxia,Xu, Daqian,Xia, Chungu,Sun, Wei
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- Synthesis of a polymer–ruthenium complex Ru(pbbp)(pydic) and its catalysis in the oxidation of secondary alcohols with TBHP as oxidant
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A polymer–ruthenium complex Ru(pbbp)(pydic) was synthesized from the reaction of poly-2,6-bis(benzimidazolyl)pyridine (pbbp) with RuCl3 and disodium pyridine-2,6-dicarboxylate (pydic). The Ru(pbbp)(pydic) was characterized thoroughly by spectroscopic methods. ICP analysis revealed that the percentage of complexation of 2,6-bis(benzimidazolyl)pyridine unit in pbbp was about 83%. The complex was tested as a heterogeneous catalyst for the oxidation of secondary alcohols to their corresponding carbonyl compounds in solvent-free conditions using aqueous tert-butyl hydroperoxide as oxidant. The developed catalytic system exhibited high activity and broad functional group compatibility, allowing a variety of secondary alcohols, including substituted secondary benzylic alcohols and secondary aliphatic ones, to be oxidized to the corresponding ketones in high yields. This Ru(pbbp)(pydic) could be recycled for several times, but it dissolved in part in the reaction mixture during the catalytic run leading to gradual deactivation of the catalyst with repeated runs.
- Zhang, Yuecheng,Chu, Ruosi,Zhang, Hongyu,Zhao, Jiquan
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- Aerobic oxidation of secondary alcohols using NHPI and iron salt as catalysts at room temperature
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Aerobic oxidation of various alcohols has been accomplished by using a novel catalytic system, N-hydroxyphthalimide (NHPI) combined with Fe(NO 3)3·9H2O. Secondary alcohols, especially benzylic and aliphatic alcohols, were smoothly transformed into corresponding ketones with up to 92% yields at room temperature under one atmosphere pressure of oxygen. The influences of reaction conditions such as solvent, different metal catalyst, catalyst loading and the structure of alcohols on the promotion effect were studied. And a possible radical mechanism for the oxidation of secondary alcohols in Fe(NO3)3·9H 2O/NHPI/O2 system was proposed.
- Zhao, Hanqing,Sun, Wei,Miao, Chengxia,Zhao, Quanyi
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- Chelation-Assisted C-H and C-C Bond Activation of Allylic Alcohols by a Rh(I) Catalyst under Microwave Irradiation
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Chelation-assisted Rh(I)-catalyzed ketone synthesis from allylic alcohols and alkenes through C-H and C-C bond activations under microwave irradiation was developed. Aldimine is formed via olefin isomerization of allyl alcohol under Rh(I) catalysis and condensation with 2-amino-3-picoline, followed by continuous C-H and C-C bond activations to produce a dialkyl ketone. The addition of piperidine accelerates the reaction rate by promoting aldimine formation under microwave conditions.
- Lee, Chang-Hee,Jun, Chul-Ho
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- Efficient oxidation of secondary alcohols to ketones by NaOCl catalyzed by salen-Mn(III)/NBS
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An efficient catalytic system salen-Mn(III)/NBS for oxidation of secondary alcohols to ketones by inexpensive and readily available oxidizing agent NaOCl has been developed. The process resulted in good to excellent yields under the action of 2 mol % of salen-Mn(III) and 13 mol % of NBS at room temperature. However, such system was not efficient in oxidation of secondary benzyl alcohols with a strong electronicdonating substituent attached to the benzene ring due to bromination of the alcohols.
- Zhang,Lü,Cui,Zhao
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- Pd-H from Pd/C and triethylamine: Implications in palladium catalysed reactions involving amines
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The palladium hydride-iminium complex generated from Pd/C and triethylamine catalyses the isomerisation of allylic alcohols into carbonyl compounds, and Pd/C catalyses the conjugate reduction of activated double bonds using triethylamine as the source of the two newly incorporated hydrogen atoms via the same complex.
- Coquerel, Yoann,Brémond, Paul,Rodriguez, Jean
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- Modular counter-Fischer?indole synthesis through radical-enolate coupling
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A single-electron transfer mediated modular indole formation reaction from a 2-iodoaniline derivative and a ketone has been developed. This transition-metal-free reaction shows a broad substrate scope and unconventional regioselectivity trends. Moreover, important functional groups for further transformation are tolerated under the reaction conditions. Density functional theory studies reveal that the reaction proceeds by metal coordination, which converts a disfavored 5-endo-trig cyclization to an accessible 7-endo-trig process.
- Chung, Hyunho,Kim, Jeongyun,Gonzalez-Montiel, Gisela A.,Cheong, Paul Ha-Yeon,Lee, Hong Geun
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p. 1096 - 1102
(2021/01/26)
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- Aromatic compound hydrogenation and hydrodeoxygenation method and application thereof
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The invention belongs to the technical field of medicines, and discloses an aromatic compound hydrogenation and hydrodeoxygenation method under mild conditions and application of the method in hydrogenation and hydrodeoxygenation reactions of the aromatic compounds and related mixtures. Specifically, the method comprises the following steps: contacting the aromatic compound or a mixture containing the aromatic compound with a catalyst and hydrogen with proper pressure in a solvent under a proper temperature condition, and reacting the hydrogen, the solvent and the aromatic compound under the action of the catalyst to obtain a corresponding hydrogenation product or/and a hydrodeoxygenation product without an oxygen-containing substituent group. The invention also discloses specific implementation conditions of the method and an aromatic compound structure type applicable to the method. The hydrogenation and hydrodeoxygenation reaction method used in the invention has the advantages of mild reaction conditions, high hydrodeoxygenation efficiency, wide substrate applicability, convenient post-treatment, and good laboratory and industrial application prospects.
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Paragraph 0094-0095; 0123-0125; 0127-0130
(2021/05/29)
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- Multiple Mechanisms Mapped in Aryl Alkyl Ether Cleavage via Aqueous Electrocatalytic Hydrogenation over Skeletal Nickel
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We present here detailed mechanistic studies of electrocatalytic hydrogenation (ECH) in aqueous solution over skeletal nickel cathodes to probe the various paths of reductive catalytic C-O bond cleavage among functionalized aryl ethers relevant to energy science. Heterogeneous catalytic hydrogenolysis of aryl ethers is important both in hydrodeoxygenation of fossil fuels and in upgrading of lignin from biomass. The presence or absence of simple functionalities such as carbonyl, hydroxyl, methyl, or methoxyl groups is known to cause dramatic shifts in reactivity and cleavage selectivity between sp3 C-O and sp2 C-O bonds. Specifically, reported hydrogenolysis studies with Ni and other catalysts have hinted at different cleavage mechanisms for the C-O ether bonds in α-keto and α-hydroxy β-O-4 type aryl ether linkages of lignin. Our new rate, selectivity, and isotopic labeling results from ECH reactions confirm that these aryl ethers undergo C-O cleavage via distinct paths. For the simple 2-phenoxy-1-phenylethane or its alcohol congener, 2-phenoxy-1-phenylethanol, the benzylic site is activated via Ni C-H insertion, followed by beta elimination of the phenoxide leaving group. But in the case of the ketone, 2-phenoxyacetophenone, the polarized carbonyl πsystem apparently binds directly with the electron rich Ni cathode surface without breaking the aromaticity of the neighboring phenyl ring, leading to rapid cleavage. Substituent steric and electronic perturbations across a broad range of β-O-4 type ethers create a hierarchy of cleavage rates that supports these mechanistic ideas while offering guidance to allow rational design of the catalytic method. On the basis of the new insights, the usage of cosolvent acetone is shown to enable control of product selectivity.
- Hegg, Eric L.,Jackson, James E.,Klinger, Grace E.,Saffron, Christopher M.,Zhou, Yuting
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p. 4037 - 4050
(2020/03/10)
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- Selective hydrogenation of aromatic compounds using modified iridium nanoparticles
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Till now, Ionic liquid-stabilized metal nanoparticles were investigated as catalytic materials, mostly in the hydrogenation of simple substrates like olefins or arenes. The adjustable hydrogenation products of aromatic compounds, including quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes, are always of special interest, since they provide more choices for additional derivatization. Iridium nanoparticles (Ir NPs) were synthesized by the H2 reduction in imidazolium ionic liquid. TEM indicated that the Ir NPs is worm-like shape with the diameter around 12.2?nm and IR confirmed the modification of phosphine-functionalized ionic liquids (PFILs) to the Ir NPs. With the variation of the modifier, solvent and reaction temperature, substrate like quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes could be hydrogenated by Ir NPs with interesting adjustable catalytic activity and chemoselectivity. Ir NPs modified by PFILs are simple and efficient catalysts in challenging chemoselective hydrogenation of quinoline and relevant compounds, aromatic nitro compounds, aromatic ketones as well as aromatic aldehydes. The activity and chemoselectivity of the Ir NPs could be obviously impacted or adjusted by altering the modifier, solvent and reaction temperature.
- Jiang, He-Yan,Xu, Jie,Sun, Bin
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- Manganese complex-catalyzed oxidation and oxidative kinetic resolution of secondary alcohols by hydrogen peroxide
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The highly efficient catalytic oxidation and oxidative kinetic resolution (OKR) of secondary alcohols has been achieved using a synthetic manganese catalyst with low loading and hydrogen peroxide as an environmentally benign oxidant in the presence of a small amount of sulfuric acid as an additive. The product yields were high (up to 93%) for alcohol oxidation and the enantioselectivity was excellent (>90% ee) for the OKR of secondary alcohols. Mechanistic studies revealed that alcohol oxidation occurs via hydrogen atom (H-atom) abstraction from an α-CH bond of the alcohol substrate and a two-electron process by an electrophilic Mn-oxo species. Density functional theory calculations revealed the difference in reaction energy barriers for H-atom abstraction from the α-CH bonds of R- and S-enantiomers by a chiral high-valent manganese-oxo complex, supporting the experimental result from the OKR of secondary alcohols.
- Miao, Chengxia,Li, Xiao-Xi,Lee, Yong-Min,Xia, Chungu,Wang, Yong,Nam, Wonwoo,Sun, Wei
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p. 7476 - 7482
(2017/10/30)
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- Immobilization of Ru(terpyridine)(2,6-pyridinedicarboxylate) onto MCM-41 and its catalysis in the oxidation of alcohols
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The ruthenium complex Ru(terpyridine)(2,6-pyridinedicarboxylate) was successfully grafted onto MCM-41 using a multi-step grafting method. The immobilized ruthenium complex was characterized thoroughly using Fourier transform infrared, Raman, UV–visible diffuse reflectance and energy-dispersive X-ray spectroscopies, X-ray diffraction, N2 adsorption, scanning electron microscopy, thermogravimetric analysis and inductively coupled plasma analysis. This immobilized ruthenium complex showed excellent performance in the oxidation of various secondary alcohols to their corresponding ketones with tert-butyl hydroperoxide as oxidant under solvent-free conditions, and had the advantages of easy recovery and good reusability.
- Zhang, Yuecheng,Sun, Xiaochen,Zhang, Hongyu,Zhao, Jiquan
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p. 645 - 652
(2016/07/19)
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- Tuning the chemoselective hydrogenation of aromatic ketones, aromatic aldehydes and quinolines catalyzed by phosphine functionalized ionic liquid stabilized ruthenium nanoparticles
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Ruthenium nanoparticles (Ru NPs) stabilized by phosphine-functionalized ionic liquids (PFILs) were synthesized in an imidazolium-based ionic liquid using H2 as a reductant. Characterization showed well-dispersed particles of about 2.2 nm (TEM) and confirmed the PFIL stabilization of the Ru NPs (NMR). The Ru NPs stabilized by PFILs exhibited excellent activity and switchable chemoselectivity in the heterogeneous selective hydrogenation of aromatic ketones, aromatic aldehydes and quinolines under mild conditions.
- Jiang, He-Yan,Zheng, Xu-Xu
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p. 3728 - 3734
(2015/07/07)
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- Highly Selective Hydrogenation of Aromatic Ketones and Phenols Enabled by Cyclic (Amino)(alkyl)carbene Rhodium Complexes
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Air-stable Rh complexes ligated by strongly σ-donating cyclic (amino)(alkyl)carbenes (CAACs) show unique catalytic activity for the selective hydrogenation of aromatic ketones and phenols by reducing the aryl groups. The use of CAAC ligands is essential for achieving high selectivity and conversion. This method is characterized by its good compatibility with unsaturated ketones, esters, carboxylic acids, amides, and amino acids and is scalable without detriment to its efficiency.
- Wei, Yu,Rao, Bin,Cong, Xuefeng,Zeng, Xiaoming
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supporting information
p. 9250 - 9253
(2015/08/11)
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- 4-CH3CONH-TEMPO/Peracetic Acid System for a Shortened Electron-Transfer-Cycle-Controlled Oxidation of Secondary Alcohols
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We have developed a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) derivative catalyzed oxidation of secondary alcohols with peracetic acid as the oxidant, which was generated from H2O2 and acetic acid catalyzed by strongly acidic resins. The oxidation of alcohols proceeded well through a shortened electron-transfer cycle under metal-free conditions, avoiding the use of any other electron-transfer mediators such as halides. In addition, we demonstrated that the present system exhibited excellent efficiency under mild conditions for the oxidation of aromatic, aliphatic, and allylic secondary alcohols. Shortcut to ketones: The 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-derivative-catalyzed oxidation of secondary alcohols employing peracetic acid generated from H2O2 and acetic acid with strongly acidic resins proceeds through a shortened electron-transfer cycle without halide additives. The system not only exhibits excellent efficiency at room temperature but also has a wide substrate scope.
- Zhang, Shufang,Miao, Chengxia,Xia, Chungu,Sun, Wei
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p. 1865 - 1870
(2015/06/23)
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- Discovery of biological evaluation of pyrazole/imidazole amides as mGlu5 receptor negative allosteric modulators
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Development of SAR in a 5-aryl-3-acylpyridinyl-pyrazoles and 1-aryl-4-acylpyridinyl imidazoles series of mGlu5 receptor negative allosteric modulators (mGluR5 NAMs) using a functional cell-based assay is described in this Letter. Analysis of the Ligand-lipophilic efficiency (LipE) of compounds provided new insight for the design of potent mGluR5 negative allosteric modulators with anti-depressant activities.
- Chae, Eunhee,Shin, Yong-Je,Ryu, Eun-Ju,Ji, Mi Kyung,Ryune Cho, Nahm,Lee, Ki-Ho,Jeong, Hyun Ji,Kim, Soo-Jin,Choi, Yeonjung,Seok Oh, Kyung,Park, Chun-Eung,Soo Yoon, Young
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p. 2134 - 2139
(2013/05/09)
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- The Mn(Salen)-catalyzed oxidative kinetic resolution of secondary alcohols: reaction development and scope
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A series of chiral Mn(Salen) complexes have been synthesized and submitted to the kinetic resolution of secondary alcohols bearing a large hindrance in the biphasic system, which is composed of water and CH2Cl2. After evaluating the appropriate complex, additive, and other conditions, chiral secondary alcohols were obtained with enantiomeric excesses of up to 98.6% in 6 min.
- Cheng, Qigan,Deng, Fanguo,Xia, Chungu,Sun, Wei
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experimental part
p. 2359 - 2362
(2009/04/11)
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- Hydroboration with pyridine borane at room temperature
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Treatment of pyridine borane (Py·BH3) with iodine, bromine, or strong acids affords activated Py·BH2X complexes that are capable of hydroborating alkenes at room temperature. Evidence is presented for an unusual hydroboration mechanism involving leaving group displacement. In contrast to THF·BH3, hydroboration with Py·BH2I selectively affords the monoadducts. The crude hydroboration products are converted into synthetically useful potassium alkyltrifluoroborate salts upon treatment with methanolic KHF2. Copyright
- Clay, Julia M.,Vedejs, Edwin
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p. 5766 - 5767
(2007/10/03)
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- Synthesis, biological evaluation, and structural studies on N1 and C5 substituted cycloalkyl analogues of the pyrazole class of CB1 and CB2 ligands
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A series of N1 and C5 substituted cycloalkyl and C5 4-methylphenyl analogues of the N-(piperidin-1-yl)-4-methyl-1H-pyrazole-3-carboxamide class of cannabinoid ligands were synthesized. The analogues were evaluated for CB1 and CB2 receptor binding affinities and receptor subtype selectivity. The effects of pyrazole substitution on ligand conformation and as such receptor affinities was not readily apparent; therefore, the geometries of the N1 and C5 substituents relative to the pyrazole ring were studied using high field NMR spectroscopy and systematic molecular mechanics geometry searches. An analysis of the relative ring geometries and functional group orientations provides new insight into the structural requirements of the CB1 and CB2 ligand binding pocket.
- Krishnamurthy, Mathangi,Li, Wei,Moore II, Bob M.
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p. 393 - 404
(2007/10/03)
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- Stereocontrol in hydride addition to ketone-derived chiral N-acylhydrazones
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Chiral N-acylhydrazones derived from various aldehydes and N-amino-4-benzyl-2-oxazolidinone have previously been shown to be effective for acyclic stereocontrol of intermolecular radical and allylsilane additions. Treatment of the propionaldehyde hydrazone with tributyltin hydride in the presence of boron trifluoride etherate led to rapid chemoselective reduction of the imine bond in high yield. Preparation of similar hydrazones from ketones led to E/Z isomer mixtures, usually in ratios of 4:1 or greater. Geometry of the C=N bond was assigned by steric compression shifts in 13C NMR spectra. Reduction with tributyltin hydride and boron trifluoride etherate afforded diastereomer mixtures in ratios very similar to the original E/Z isomer ratios. The chiral auxiliary blocked the opposite face of the C=N bond relative to a related process using a chelated Lewis acid. A stereocontrol model involving monodentate interaction of the N-acylhydrazone and boron trifluoride is consistent with the observed stereochemical outcome.
- Qin, Jun,Friestad, Gregory K.
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p. 6393 - 6402
(2007/10/03)
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- Desilylation and conversion of trimethylsilylmethyl epoxides into ketones under the influence of a bulky base
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Trimethylsilylmethyl epoxides were converted into ketones through a desilylation, epoxide ring-opening, and rearrangement reaction under the influence of a bulky base in the presence of 18-crown-6.
- Ma, Yuan
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p. 310 - 315
(2007/10/03)
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- Hydrodehalogenation of halogenated aryl ketones under multiphase conditions. 6. pH effect on the chemoselectivity and preliminary mechanistic investigation
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A model halogenated aryl ketone (4-chloropropiophenone 1) was subjected to mild catalytic hydrodehalogenation (p[H2] = 1 arm, T = 50°C) in a multiphase system consisting of isooctane and an alkaline aqueous phase, in the presence of onium salts as phase-transfer agents. The chemoselectivity of the reaction was sharply influenced by the KOH concentration of the aqueous phase: thus, the formation of 1-phenyl-l-propanol 4 was favored in a highly alkaline pH range (>13.5 by 50% to 5% KOH(aq)). Instead, up to 95% selectivity toward phenyl ethyl ketone 2 was observed if the pH was controlled (8 pH 13) by adjusting the KOH(aq) concentration in the range between 5 and 1%. Further investigation of the pH effect indicated that an acidic aqueous phase directed the reaction chemoselectivity toward the formation of products arising from aromatic ring reduction (i.e., cyclohexyl ethyl ketone 7 and 1-cyclohexyl-1-propanol 8) rather than from carbonyl hydrogenation or hydrogenolysis. Also aliphatic amines, used in place of the PT onium salt, afforded good selectivities toward 2, although not as high as the ones obtained with Aliquat 336.
- Perosa, Alvise,Selva, Maurizio,Tundo, Pietro
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p. 3934 - 3939
(2007/10/03)
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- Hydrodehalogenation of Halogenated Aryl Ketones under Multiphase Conditions. 5. Chemoselectivity toward Aryl Alcohols over a Pt/C Catalyst
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Halogenated aryl ketones (XC6H4COR: X = Cl, F; R = Me, Et, Ph) and benzyl alcohols (XC6H4-CH(OH)R: X = Cl; R = Me, Et) have been reduced catalytically over Pt/C at 50 °C, by bubbling H2 at atmospheric pressure into a multiphase system consisting of a hydrocarbon solvent (isooctane) and an alkaline aqueous phase (KOH 50%) in the presence of a phase-transfer (PT) agent (onium salts or polyoxyethylene monoalkyl ethers). The chemoselectivity of the reaction is sharply modified by the PT-agent: in its absence, a wide range of products is observed, including those deriving from the complete reduction of both the aromatic ring and carbonyl functions. Instead, the presence of the PT-agent allows several different halo ketones to be transformed into their corresponding benzylic alcohols: that is, the hydrodechlorination occurs only with the partial hydrogenation of the CO group to the CH(OH) one, while further reductions are totally prevented. Under such conditions, both ionic (onium salts) and nonionic (polyoxyethylene monoalkyl ethers: Brij 35, 52, 56, and 58) compounds have been tested, and results seem to suggest that the higher their hydrophilicity is, the better the chemoselectivity toward the formation of dehalogenated alcohols is as well. Moreover, under multiphase conditions, also halo aryl alcohols lead to the corresponding dechlorinated alcohols in quantitative yields although a slower reaction is observed with respect to ketones.
- Selva, Maurizio,Tundo, Pietro,Perosa, Alvise
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p. 3266 - 3271
(2007/10/03)
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- Selective homologation of ketones and aldehydes with diazoalkanes promoted by organoaluminum reagents
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Organoaluminum-promoted single homologation or ring expansion of ketones and aldehydes with diazoalkanes has been described, and among various organoaluminium reagents, exceptionally bulky methylaluminum bis(2,6-di-tert-butyl-4-methylphenoxide) (MAD) is found to be highly effective for the selective homologation of various ketones and aldehydes.
- Maruoka,Concepcion,Yamamoto
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p. 1283 - 1290
(2007/10/02)
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- Chemoselectivity in the ruthenium-catalyzed redox isomerization of allyl alcohols
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Adjustment of oxidation level by internal hydrogen reorganization represents a highly efficient synthetic protocol. Cyclopentadienylbis(triphenylphosphine)ruthenium chloride in the presence of triethylammonium hexafluorophosphate catalyzes the redox isomerization of allyl alcohols to their saturated aldehydes or ketones. High chemoselectivity is observed since simple primary and secondary alcohols and isolated double bonds are not affected by this catalyst. The reaction is sensitive to the degree of substitution on the double bond and requires relatively unhindered olefins. Switching to indenylbis(triphenylphosphine)ruthenium chloride in the presence of triethylammonium hexafluorophosphate significantly expands the scope of the reaction to substrates bearing more substituted olefinic linkages and to cyclic substrates of rings containing eight or more members. The mechanism is probed by deuterium labeling, which shows that the metal catalyzes an intramolecular 1,3-hydrogen shift of the carbinol hydrogen to the terminal olefinic position.
- Trost, Barry M.,Kulawiec, Robert J.
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p. 2027 - 2036
(2007/10/02)
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- Stereoselective Reduction of γ-Oxobutanoic Acids Using DIBAL-H and ZnCl2
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A variety of γ-aromatic γ-ketobutanoic acids can be reduced selectively, under optimized conditions, by the use of DIBAL-H and ZnCl2 to provide the (RS,SR)-γ-aryl-γ-hydroxy-β-methylbutanoic acids.Further evidence has been gathered to support the hypothesis that the reaction proceeds by formation of a seven-membered ring complex with the aluminium or zinc atom bridging the ketone and carboxyl groups which preceeds the reduction step and that this templated reduction accounts for observed high diastereoselectivity.Also we have shown that some γ-aryl-γ-butyrolactones can be easily transformed via an oxidative cleavage of the aromatic ring to provide selective synthesis of either cis- or trans-tetrahydro-3-methyl-5-oxo-2-furancarboxylic acid derivatives.
- Frenette, R.,Monette, M.,Bernstein, M. A.,Young, R. N.,Verhoeven, T. R.
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p. 3083 - 3089
(2007/10/02)
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- A chemoselective internal redox of allyl alcohols to saturated aldehydes or ketones
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Cp(Ph3P)2RuCl efficiently isomerizes allyl alcohols to saturated aldehydes or ketones even in the presence of other olefins and saturated alcohols.
- Trost, Barry M.,Kulawiec, Robert J.
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p. 3039 - 3042
(2007/10/02)
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- ADDITION RADICALAIRE DU PROPANAL A DIVERS ALCENES ET CYCLENES : ASPECTS STERIQUES ET POLAIRES
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Free radical addition of propanal to double bonds, initiated by benzoyl peroxide, mainly leads to two adducts, an aldehyde and a ketone, when the double bond has a methylene group ; these results are explained in terms of polar effects in the free radical transfert reactions.When the double bond has no methylene group, only the ketonic adduct is obtained ; the steric effects in the free radical addition step explain these results.
- Tabbaa, I.,Cazaux, M.,Lalande, R.
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p. 1011 - 1018
(2007/10/02)
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- Dipole-Stabilized Carbanions from Esters: α-Oxo Lithiations of 2,6-Substituted Benzoates of Primary Alcohols
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The synthetic utility of dipole-stabilized carbanions from esters is illustrated by the preparations, α-oxo lithiations, electrophilic substitutions, and cleavages of the 2,4,6-triisopropylbenzoates and the 2,6-bis(dimethylamino)-3,5-diisopropylbenzoates of primary alcohols, 2 and 3, respectively.Typical electrophiles used in this methodology include primary alkyl halides, aldehydes, ketones, trimethylsilyl chloride, and tri-n-butyltin chloride.Cleavages of the substituted esters of 2 are accomplished with lithium aluminum hydride while hydrolyses of derivatives of3 can be achieved under acidic conditions.The 2,6-substitutions of 2 and 3 are considered to enforce orthogonality of the carbonyl group and the phenyl ring and thereby to inhibit addition to the carbonyl by the organolithium base used for the metalation by placing the substituents in the trajectory for nucleophilic addition along the LUMO of the carbonyl.The acidic hydrolysis of 3 under conditions where 2 is stable is attributed to protonation of the dimethylamino group which provides subsequent assistance for nucleophilic addition.These metalations provide the key steps in the preparation of secondary α-lithio alcohol synthetic equivalents from primary alcohols.Lithiation of 1'-methylbenzyl 2,4,6-triisopropylbenzoate proceeds α to oxygen as expected, but attempts to prepare analogous unactivated tertiary α-lithio esters were unsuccessful.The lithiation of 2'-methoxyethyl 2,4,6-triisopropylbenzoate is followed by elimination of methoxide and α-oxo metalation of the resulting vinyl ester.Lithiation of allyl 2,4,6-triisopropylbenzoate provides 1-(2,4,6-triisopropylphenyl)-1,2-butanedione by rearrangement.
- Beak, Peter,Carter, Linda G.
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p. 2363 - 2373
(2007/10/02)
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- Ketone synthesis by hydroacylation
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The invention is a generalized hydroacylation reaction. The reaction involves the activation of a selected aldehyde by converting by iminization to an aldimine or an aminal. The imine group replaces the carbonyl group. The imine C-H bond is then susceptible to attack by a chosen olefin, and hydrolysis to yield the ketone. One moiety of the ketone derives from the aldehyde and the other from the olefin added later. Therefore, the ketone may be symmetrical or unsymmetrical. Both aromatic and aliphatic aldehydes may be activated according to this process.
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- ANOMALOUS CLEAVAGE OF GLYCIDIC ACIDS
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The esters of 3-cyclohexyl- and 3-(2,2-dimethyl-4-tetrahydropyranyl)-2-methyl-2,3-epoxypropionic acids were obtained by the reaction of cyclohexanecarbaldehyde and 2,2-dimethyltetrahydro-4-pyrancarbaldehye with 2-chloropropionic esters.Decarboxylation of the acids corresponding to the obtained esters takes place through cleavage of the oxide ring at the C2 atom.
- Kuroyan, R. A.,Markosyan, A. I.,Engoyan, A. P.,Vartanyan, S. A.
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p. 2219 - 2221
(2007/10/02)
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- Malonate Anion Induced Favorskii-Type Rearrangement. Reaction of Cyclic α-Halo Ketones with Sodiomalonates
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The reaction of 2-chlorocyclohexanone (1b) with ethyl sodiomalonate in benzene at 0-25 deg C gave 6-bicyclohexan-6-ol (4c), the Favorskii-type intermediate, in 49percent yield, in place of the substitution product ethyl C-(2-oxocyclohexyl)malonate (3).Derivatives of bicycloheptan-7-ol (4a,b) and those of bicyclohexan-6-ol (4d,e) were also obtained in good yields by similar means.Compound 4c was transformed into 3 readily by heating with 0.05 equiv of NaH in benzene.The hydrolysis of 4a-d with 0.2 N NaOH followed by pyrolysis at 110-120 deg C gave the ring-contracted β-keto esters 9a-d.Pyrolysis after the hydrolysis with 2N NaOH gave the corresponding ketones 11a-d in good yields.Oxidation of 4c with CrO3 and HClO4 afforded ethyl C-(2-hydroxycyclopentanecarbonyl)malonate (14) in 45 percent yield.Treatment of 4c with Br2 gave ethyl C-(1-bromocyclopentanecarbonyl)malonate (18) in 64 percent yield.
- Sakai, Takashi,Amano, Eiichiro,Kawabata, Akifumi,Takeda, Akira
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- Acyl anion equivalents: Synthesis of ketones and enones from α-phenylthioalkylphosphine oxides
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The sulphenylated phosphine oxides Ph2P(O)·CH(SR2R1, easily prepared from triphenylphosphine, diphenyl or dimethyl disulphide, and an alkyl halide, form anions which act as acyl anion equivalents. Reaction with aldehydes and ketones gives vinyl sulphides, which can be hydrolysed to carbonyl compounds. Reaction with α-phenylthio-and α-methoxy-aldehydes and ketones gives enone precursors. The scope and limitations of the method are described.
- Grayson, J. Ian,Warren, Stuart
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p. 2263 - 2272
(2007/10/05)
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