- Solvent free ion exchange catalysis in the oxidation of organic compounds with sodium bromate
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The oxidation of organic compounds under solvent free ion exchange resin (IER) catalysis by sodium bromate has been studied at room temperature. Primary benzylic and secondary alcohols are converted to aldehydes and ketones and alkylarenes are oxidized to the corresponding α-ketones. The experimental procedure is simple and products are easily isolated in high yields at room temperature.
- Shaabani, Ahmad,Lee, Donald G.
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Read Online
- Deciphering Reactivity and Selectivity Patterns in Aliphatic C-H Bond Oxygenation of Cyclopentane and Cyclohexane Derivatives
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A kinetic, product, and computational study on the reactions of the cumyloxyl radical with monosubstituted cyclopentanes and cyclohexanes has been carried out. HAT rates, site-selectivities for C-H bond oxidation, and DFT computations provide quantitative information and theoretical models to explain the observed patterns. Cyclopentanes functionalize predominantly at C-1, and tertiary C-H bond activation barriers decrease on going from methyl- and tert-butylcyclopentane to phenylcyclopentane, in line with the computed C-H BDEs. With cyclohexanes, the relative importance of HAT from C-1 decreases on going from methyl- and phenylcyclohexane to ethyl-, isopropyl-, and tert-butylcyclohexane. Deactivation is also observed at C-2 with site-selectivity that progressively shifts to C-3 and C-4 with increasing substituent steric bulk. The site-selectivities observed in the corresponding oxidations promoted by ethyl(trifluoromethyl)dioxirane support this mechanistic picture. Comparison of these results with those obtained previously for C-H bond azidation and functionalizations promoted by the PINO radical of phenyl and tert-butylcyclohexane, together with new calculations, provides a mechanistic framework for understanding C-H bond functionalization of cycloalkanes. The nature of the HAT reagent, C-H bond strengths, and torsional effects are important determinants of site-selectivity, with the latter effects that play a major role in the reactions of oxygen-centered HAT reagents with monosubstituted cyclohexanes.
- Martin, Teo,Galeotti, Marco,Salamone, Michela,Liu, Fengjiao,Yu, Yanmin,Duan, Meng,Houk,Bietti, Massimo
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supporting information
p. 9925 - 9937
(2021/06/30)
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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 0094-0097; 0100-0104
(2021/05/29)
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- Trans-Selective and Switchable Arene Hydrogenation of Phenol Derivatives
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A trans-selective arene hydrogenation of abundant phenol derivatives catalyzed by a commercially available heterogeneous palladium catalyst is reported. The described method tolerates a variety of functional groups and provides access to a broad scope of trans-configurated cyclohexanols as potential building blocks for life sciences and beyond in a one-step procedure. The transformation is strategically important because arene hydrogenation preferentially delivers the opposite cis-isomers. The diastereoselectivity of the phenol hydrogenation can be switched to the cis-isomers by employing rhodium-based catalysts. Moreover, a protocol for the chemoselective hydrogenation of phenols to cyclohexanones was developed.
- Bergander, Klaus,Glorius, Frank,Heusler, Arne,Wollenburg, Marco
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p. 11365 - 11370
(2020/11/24)
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- Selective phenol hydrogenation under mild condition over Pd catalysts supported on Al2O3 and SiO2
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Cyclohexanone (CHONE) is the key intermediate in the manufacture of nylon-6 and nylon-66. Selective hydrogenation of phenol into CHONE was investigated over Pd/SiO2 and Pd/Al2O3. The results show that the yield of CHONE reaches 98% or more over Pd/Al2O3 and Pd/SiO2 at 333?K under atmospheric pressure in cyclohexane solvent. High activity of Pd/Al2O3 is promoted by Lewis acidity, and phenol can be converted 100% within 300?min. The hydrogenation of CHONE occurs until the conversion of phenol approaches completion. Pd/SiO2 with smaller Pd nano-particles presents higher selectivity. For polar solvent, such as ethanol and dichloromethane, the activity of Pd catalysts decreases greatly. Auxiliary experiments verify that phenol adsorbs on Pd catalysts via the formation of π–c with an aromatic ring. Increased hydrogen pressure not only promotes significantly the rates of hydrogenation, but also increases the selectivity for CHONE, especially over Pd/SiO2-1 catalyst.
- Li, Xinzheng,Cheng, Ling,Wang, Xingyi
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p. 1249 - 1262
(2019/02/24)
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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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- Titanium silicates as efficient catalyst for alkylation and acylation of silyl enol ethers under liquid-phase conditions
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The activity of titanium- and tin-silicate samples such as TS-1, TS-2, Ti-β and Sn-MFI has been investigated for acylation and alkylation of silyl enol ethers under mild liquid-phase conditions. Silyl enol ethers successfully react with acetyl chloride and tert-butyl chloride under dry conditions in the presence of above catalysts to produce the corresponding acylated and alkylated products, respectively. In the case of acetylation reaction, two different nucleophiles with carbon-center (C-atom) and oxygen-center (O-atom) in silyloxy group of silyl enol ether reacts with acetyl chloride to give 1,3-diketone and ketene-ester, respectively. The selectivity for alkylation is always ca. 100% and no side products are formed. Among the various solvents investigated, anhydrous THF was found to be the suitable solvent for alkylation; whereas dichloromethane exhibited high selectivity for diketones for acylation. The formation of nucleophiles from silyl enol ethers appears to be the key step for successful acetylation and tert-butylation by nucleophilic reaction mechanism. Sn-MFI showed less activity than that observed over the titanosilicates. The observed catalytic activity is explained on the basis of "oxophilic Lewis acidity" of titanium silicate molecular sieves in the absence of H 2O under dry reaction conditions.
- Sasidharan, Manickam,Bhaumik, Asim
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experimental part
p. 87 - 93
(2011/10/12)
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- Studies towards the taming of the 'carbocation' in the regioselective ring opening of epoxides to allylic alcohols
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Regioselective isomerisation of epoxides to allylic alcohols can be achieved using p-toluenesulfonic acid in the presence of 1,3- dimethylimidazolidin-2-one. Georg Thieme Verlag Stuttgart.
- Chapman, Helen A.,Herbal, Karim,Motherwell, William B.
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experimental part
p. 595 - 598
(2010/09/15)
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- Stereoselective hydrogenation of tert-butylphenols over charcoal-supported rhodium catalyst in supercritical carbon dioxide solvent
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Hydrogenation of 2-, 3-, and 4-tert-butylphenols was studied over a charcoal-supported rhodium catalyst in supercritical carbon dioxide (scCO2) solvent, and the results were compared with those in organic solvents. In the hydrogenation of 4-ter
- Hiyoshi, Norihito,Rode, Chandrashekhar V.,Sato, Osamu,Tetsuka, Hiroyuki,Shirai, Masayuki
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- α-alkylation of ketones by addition of zinc enamides to unactivated olefins
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A zinc enamide generated from the corresponding N-aryl imine undergoes addition to an unactivated olefin, such as ethylene, 1-octene, and isobutylene, to generate an α-alkylated γ-zincioimine intermediate in good to excellent yield. Terminal and gem-disubstituted olefins react with >99% regioselectivity, allowing the C-C bond formation to take place at the more hindered carbon of the double bond. The organozinc intermediate undergoes further C-C bond formation with a carbon electrophile to give, upon hydrolysis of the imine, an α-alkylated ketone bearing a variety of functionalized primary, secondary, and tertiary alkyl groups.
- Nakamura, Masaharu,Hatakeyama, Takuji,Nakamura, Eiichi
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p. 11820 - 11825
(2007/10/03)
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- Cerium(III) bromate as a new reagent in oxidation of organic compounds
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Cerium(III) bromate, prepared by the reaction of barium bromate with cerium(III) sulfate, can be used for the oxidation of alkylarenes, alcohols, and sulfides. Products are obtained in high yields under mild conditions. Ce(BrO3)3 is an unique, dual property reagent in which the anion is the oxidant and the cation a catalyst. Stoichiometric studies indicate that bromate is reduced to bromide under these conditions, making the process highly efficient.
- Shaabani, Ahmad,Lee, Donald G.
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p. 1845 - 1854
(2007/10/03)
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- Oxidation deprotection of trimethylsilyl ethers to carbonyl compounds by NaBrO3-NH4Cl reagent in aqueous acetonitrile
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Primary and secondary benzylic and secondary alkyl trimethlysilyl ethers are efficiently converted into their carbonyl compounds by NaBrO3-NH4Cl in aqueous acetonitrile. Primary alkyl silyl ethers give only the corresponding alcohols without further oxidation with NaBrO3-NH4Cl.
- Shaabani,Karimi
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p. 759 - 765
(2007/10/03)
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- Amidino derivatives useful as nitric oxide synthase inhibitors
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The current invention discloses useful pharmaceutical compositions containing amidino derivative useful as nitric oxide synthase inhibitors.
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- A practical method for alcohol oxidation with aqueous hydrogen peroxide under organic solvent- and halide-free conditions
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A catalytic system consisting of sodium tungstate and methyltrioctylammonium hydrogensulfate effects oxidation of simple secondary alcohols to ketones using 3 - 30% H2O2 without any organic solvents. The oxidation can be conducted under entirely halide-free, mildly acidic conditions. A combination of tungstic acid and an appropriate quaternary ammonium salt also effects the alcohol dehydrogenation. The organic/aqueous biphasic reaction allows easy product/catalyst separation. The turnover number, defined as tools of product per mol of catalyst, approaches 77700 (2- octanol) or 179000 (1-phenylethanol), two orders of magnitude higher than any previously reported. Ester, alkyl and t-butyldimethylsilyl ether, epoxy, carbonyl, N-alkyl carboxamide, and nitrile groups are tolerated under the reaction conditions. Secondary alcohols are preferentially oxidized over terminal olefins. Primary alkanols are oxidized directly to carboxylic acids in a moderate to high yield. Benzylic alcohols are selectively oxidized to benzaldehydes or benzoic acids under suitable conditions. This method is high-yielding, clean, safe, operationally simple, and cost-effective, and therefore suitable for practical organic synthesis. The mechanistic origin of the catalytic efficiency is discussed.
- Sato, Kazuhiko,Aoki, Masao,Takagi, Junko,Zimmermann, Klaus,Noyori, Ryoji
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p. 2287 - 2306
(2007/10/03)
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- Regioselective α-alkylation of silyl enolates using a mild catalyst- ZnCl2 doped on acidic alumina
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ZnCl2 doped acidic alumina used as a solid support acts as a better Lewis acid in the S(N)1 reaction of trimethyl silyl enol ethers with 30, allylic and benzylic halides to yield exclusively the substituted product in excellent yields. This method has been employed for the synthesis of monocyclic sesquitepene hydrocarbon, (+)-β-bisabolene and a monoterpene, 2,6-dimethyl-7-octen-4-one.
- Kad,Singh, Vasundhara,Khurana, Anupam,Chaudhary, Sangeeta,Singh, Jasvinder
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p. 3439 - 3442
(2007/10/03)
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- Oxidation of Benzylic and Secondary Alcohols to Carbonyl Compounds by NaBrO3-NH4Cl Reagent in Aqueous Acetonitrile
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NaBrO3 combined with NH4Cl is found to be an efficient reagent for the conversion, in aqueous acetonitrile and under mild conditions, of benzylic and secondary alcohols into aldehydes and ketones, respectively.
- Shaabani, Ahmad,Ameri, Majid
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p. 100 - 101
(2007/10/03)
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- Amidino dervatives useful as nitric oxide synthase inhibitors
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The current invention discloses useful pharmaceutical compositions containing azepine derivatives useful as nitric oxide synthase inhibitors.
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- The functionalization of saturated hydrocarbons. Part 24. The use of tert-butyl hydroperoxide: GoAggIV and GoAggV
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The use of tert-butyl hydroperoxide as an oxidant in Gif-type systems (GoAggIV and GoAgfV) catalyzed by various Fe(III) species is examined. Regioselectivity studids of these systems have revealed several characteristics similar to those observed for other prdviously reported Gif-type reactions. A common rdaction pathway for the GoAggIV and GoAggV oxidation systems and other Gif-type reactions (from alkane via alkyl hydroperoxide to ketone or alcohol) is seen.
- Barton, Derek H. R.,Chavasiri, Warinthorn
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- HOF·CH3CN, made directly from F2 and water, as an ecologically friendly oxidizing reagent
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The complex HOF·CH3CN, made directly from fluorine and aqueous acetonitrile, was used for oxidation of secondary alcohols and for Baeyer Villiger oxidation of ketones. By using 18O labeled reagent it was found that the ketone oxidation proceeds through the original dioxirane mechanism which Baeyer and Villiger suggested a century ago for reactions with peracids but was later discounted.
- Rozen, Shlomo,Bareket, Yifat,Kol, Moshe
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p. 8169 - 8178
(2007/10/02)
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- Axial/equatorial proportions for 2-substituted cyclohexanones
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Axial-equatorial conformational proportions have been measured for 2- substituted cyclohexanones in chloroform by the Eliel method for F, Cl, Br, I, MeO, MeS, Me2N, MeSe, and Me. For the first seven of these, at least five experimentally independent measurables were used and the resulting conformational preferences appear to be accurate to within 10%. Systematic errors degraded the results for MeSe and Me. For Me2N, the conformational preference also was measured for the first time at slow exchange in the low- temperature 13C spectrum in several solvents. In chloroform, steric and polar effects contribute to the conformational preferences, with steric effects dominant for large groups such as I and MeS.
- Basso,Kaiser,Rittner,Lambert
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p. 7865 - 7869
(2007/10/02)
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- A Convenient Preparation of Ketones by the Oxidation of Secondary Alcohols with Chromium(VI) Trioxide in Aprotic Solvent in the Presence of "Wet"-Aluminium Oxide
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The oxidation of aliphatic and alicyclic secondary alcohols with chromium(VI) trioxide in the presence of "wet"-aluminium oxide in hexane gave the corresponding ketones in excellent yields under mild conditions.
- Hirano, Masao,Nagasawa, Sonoko,Morimoto, Takashi
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p. 2857 - 2859
(2007/10/02)
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- GAS-PHASE ACID-INDUCED RING OPENING IN SUBSTITUTED 1,2-EPOXYCYCLOHEXANES
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The nature and the stereoisomeric distribution of the neutral products obtained from the gas-phase attack of radiolytically formed Broensted +, CH5+, C2H5+, and t-C4H9+> and Lewis +, t-C4H9+, and CH3FCH3+> acids on several substituted 1,2-epoxycyclohexanes have been investigated under different experimental conditions.Isolation and identification of the neutral substituted products allowed us to confirm previous indications about highly regio- and stereo-selective cationic nucleophilic displacements on these substrates occuring in the gas-phase with complete inversion of the configuration at the reaction centre (the α-C atom).In some cases, extensive acid-induced isomerization became the only observable pathway.The relative extent of the competiting substitution and isomerization was found to depend on several factors, including the structural features and internal energy of the oxonium derivative of the epoxy substrate.The results obtained from the present gas-phase experiments are discussed in relation to gas-phase and solution studies.
- Crotti, Paolo,Macchia, Franco,Pizzabiocca, Adriano,Renzi, Gabriele,Speranza, Maurizio
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p. 739 - 746
(2007/10/02)
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- Imidazolium Dichromate. A New Reagent for the Oxidation of Alcohols to Carbonyl Compounds
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Imidazolium dichromate, a stable yellow crystalline compound, is found to bee a mild selective reagent for the oxidation of allylic and benzylic alcohols to the corresponding carbonyl compounds.
- Kim, Sunggak,Lhim, Dong Chul
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p. 3297 - 3298
(2007/10/02)
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- Lewis Acids in Organic Synthesis. Approach to a Selection Strategy for Screening Experiments
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A computer-assisted strategy for selecting suitable Lewis acid catalysts in organic synthesis is described.The strategy is based on principal components (PC) analysis of measured Lewis acid properties.A two-component model accounts for 65percent of the variation in a set of 20 descriptors for 116 different Lewis acids.PC-eigenvector projections of the data allow for a systematic search of test candidates in screening experiments.The strategy is demonstrated by experimental studies on 3 Lewis acid-catalyzed reactions: alkylation of silyl enol ether, Diels-Alder reaction, and Friedel-Crafts acylation.
- Carlson, Rolf,Lundstedt, Torbjoern,Nordahl, Ake,Prochazka, Michal
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p. 522 - 533
(2007/10/02)
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- SYNTHESIS OF 1,3-DIOL DERIVATIVES FROM STERICALLY OVERCROWDED OXIRANES. RING-OPENING REACTIONS OF 1-t-BUTYL-1,2-EPOXYCYCLOHEXANE.
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The acid-catalysed ring-opening reactions of 1-t-butyl-1,2-epoxycyclohexane (1) (methanolysis, hydrolysis, and trichloroacetolysis in non-protic solvents) lead to very complex mixtures.In these reactions, in addition to the non-addition products in which the t-butyl skeleton is still present, considerable amounts of other products are formed.These compounds include 1,3-secondary addition products and other rearranged non-addition products which arise by rearrangement of the original skeleton of (1), by methyl group migration; the aldehyde (20) which is lackig both the t-butyl group and the cyclohexane skeleton is also obtained.However the opening reactions of (1) in acid media are highly regioselective, most of the reaction products arising from C-O breaking on the tertiary carbon.The structures and the configurations of all the reaction products have been well established by a study of their i.r. and n.m.r. data; however, in some cases the structures and configurations were confirmed either through unequivocal syntheses and/or chemical correlations.The stereoselectivity of the trichloroacetolysis reactions of (1) is not completely anti, even if the amounts of 1,2 adducts formed are somewhat small, and the syn/anti ratio increases with the polarity of the solvent.The results obtained were rationalized through a mechanism analogous to that previously proposed for 2-aryl- and 2-ethynyl-oxiranes in which different kinds of carbenium ion species are involved.
- Corona, Tiberio,Crotti, Paolo,Ferretti, Maria,Macchia, Franco
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p. 1607 - 1616
(2007/10/02)
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- One-pot Synthesis of 2-Substituted Cyclohexanones
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The one-pot synthesis of 2-substituted cyclohexanones involves alkylation of 2-hydroxymethylenecyclohexanone (1) in the presence of solid KOH
- Ravikumar, V. T.,Sathyamoorthi, G.,Thangaraj, K.,Rajagopalan, K.
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- N,S-DIMETHYL-S-PHENYLSULFOXIMINE. A REAGENT FOR THE OPTICAL RESOLUTION OF KETONES
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The addition of the α-lithio derivative of (+)- or (-)-N,S-dimethyl-S-phenylsulfoximine to selected dl-ketones was carried out at -78 deg C in tetrahydrofuran followed by acid quench at that temperature to produce mixtures of diastereomeric β-hydroxysulfoximines.The optically-active diastereomers were chromatographically separated on silica gel.The purified diastereomers were thermolyzed at ca. 130 deg to produce optically-active ketones and the optically-active sulfoximine which could be recycled.
- Johnson, Carl R.,Zeller, James R.
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p. 1225 - 1234
(2007/10/02)
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- Branched amides of L-aspartyl-D-amino acid dipeptides
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Amides of L-aspartyl-D-amino acid dipeptides of the formula STR1 and physiologically acceptable cationic and acid addition salts thereof wherein Ra is CH2 OH or CH2 OCH3 ; R is a branched member selected from the group consisting of fenchyl, diisopropylcarbinyl, d-methyl-t-butylcarbinyl, d-ethyl-t-butylcarbinyl, di-t-butylcarbinyl, 2-methylthio-2,4-dimethylpentan-3-yl, STR2 where at least one of R3, R4, R5, R6 is alkyl having from one to four carbon atoms and the remainder are hydrogen or alkyl having from one to four carbon atoms, X is O, S, SO, SO2, C=O or CHOH; m is zero or 1-4, n and p are each zero, 1, 2 or 3 where the sum of n+p is not greater than 3 and the sum of the carbon atoms in R3, R4, R5 and R6 is not greater than six, and when both of R3 and R4 or R5 and R6 are alkyl they are methyl or ethyl, STR3 where one of R7, R8, R9 is alkyl having from one to four carbon atoms and the remainder are hydrogen or alkyl having from one to four carbon atoms and the sum of the carbon atoms in R7, R8 and R9 is not greater than six, m and q are the same or different and each have the values previously defined for m; STR4 where each of R12 and R13 are methyl or ethyl, or R12 is hydrogen and R13 is alkyl having from one to four carbon atoms, Z is O or NH and t is 1 or 2, STR5 where W is 1-4, R14 and R16 are each alkyl having from one to four carbon atoms, R15 is H, OH, methyl or ethyl and the sum of the carbon atoms in R14, R15 and R16 is not greater than six and when both of R14 and R15 are alkyl they are methyl or ethyl, and STR6 where R17 and R19 are alkyl having from one to four carbon atoms, R18 and R20 are H or alkyl having one to two carbon atoms, A is OH and B is H, OH or CH3 and taken together A and B are STR7 where the sum of the carbon atoms in R17, R18, R19 and R20 is not greater than six and when both of R17 and R18 or R19 and R20 are alkyl they are methyl or ethyl; said amides are potent sweeteners having advantages over the prior art, edible compositions containing them, methods for their use in edible compositions and novel amide intermediates useful in their production.
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- Enones with Strained Double Bonds. 7. Precursors for Substituted Bicyclononane Systems
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Compounds 11c, 12, and 13 have been synthesized as potential precursors for the 2-substituted bicyclonon-1(2)-en-3-ones 5 (R = Ph and t-Bu).The lactone 34 and its derivatives 32 have also been synthesized as potential precursors for the parent bicyclo enone 1.
- House, Herbert O.,Outcalt, Russell J.,Cliffton, Michael D.
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p. 2413 - 2419
(2007/10/02)
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- Tertiobutylation de quelques cetones alicycliques et aliphatiques via leurs ethers d'enol trimethylsilyliques. Influence de l'environnement du carbonyle sur le deroulement de la reaction
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α-Tertiobutylation of aliphatic ketones via their trimethylsilyl enol ethers has been extended to the alicyclic series.A comparative study of the alkylation of ketones in both series with identical steric hindrance has been undertaken.The efficiency and limits of the reaction have been determinated by progressive substitution α and α' to the carbonyl.
- Lion, Claude,Dubois, Jacques-Emile
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p. 375 - 379
(2007/10/02)
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- Lewis Acid Mediated α-Alkylation of Carbonyl Compounds, VI. Optimization of the Procedure for the α-tert-Alkylation of Ketones and Aldehydes
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A simple procedure is described according to which ketones and aldehydes can be tert-alkylated at the α-position in two steps.Silyl enol ethers, which are easily accessible from the corresponding carbonyl compounds, are reacted with tert-alkyl halides in the presence of Lewis acids.Using cyclohexanone and n-butyraldehyde, the method was optimized.Tin or titanium tetrachloride in combination with tert-butyl chloride in methylene chloride at low temperatures is usually optimal.The method can be applied generally to structurally different ketones.
- Reetz, Manfred T.,Maier, Wilhelm F.,Heimbach, Horst,Giannis, Athanassios,Anastassious, Georgia
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p. 3734 - 3740
(2007/10/02)
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- Lewis Acid Mediated α-Alkylation of Carbonyl Compounds, VII. Regio and Position Specific α-tert-Alkylation of Ketones
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Structurally different ketones can be alkylated at the α-position via their silyl enol ethers with tert-alkyl halides in the presence of Lewis acids such as titanium tetrachloride (->27 - 35).Concerning the alkylation agent, the position specific introduction of branched and cyclic tert-alkyl groups is possible (->41 - 49).Bridgehead halides of the type 1-adamantyl bromide react analogously (->52 - 61).Silyl enol ethers derived from unsymmetrical ketones react regiospecifically (->63, 64, 66, 67).If the reaction partners contain additional functional groups such as aryl residues (->68, 69) or ester groups (->71) or primary alkyl halides moieties (->73), selectivity in the desired manner is observed. α,α'-Bis-tert-alkylated ketones (74 - 76) are also easily accessible, but not the α,α-isomers.
- Reetz, Manfred T.,Maier, Wilhelm F.,Chatziiosifidis, Ioannis,Giannis, Athanassios,Heimbach, Horst,Loewe, Ursula
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p. 3741 - 3757
(2007/10/02)
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