- ATOMIC FORCE MICROSCOPY AND SOLID-STATE REARRANGEMENT OF BENZOPINACOL
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The solid-solid chemical reaction of benzopinacol (1) with p-toluenesulphonic acid monohydrate (2) to give a quantitatively proton-catalysed pinacol rearrangement with formation of triphenylacetophenone (3) in the absence of a solvent was studied preparatively and mechanistically using atomic force microscopy (AFM) measurements and known crystal structure data.The reaction rate is dramatically enhanced if the water of reaction is continuously removed.AFM reveals that no reaction occurs on (001) of 1 whereas (100) exhibits distance dependent craters and volcano-like mounds over areas extending to 1.5 mm from the contact edge of the crystal with 1 undergoing phase rebuilding while reacting.A mechanism resembling the formation of membrane potentials is seen for the first time in crystals.This it appears that catalytic protons migrate without their counterions from one molecular compartment to the next by proton consumption at its inside and proton liberation at its outside, which is the inside of the next compartment.The uppermost molecular layer determines reactivity or non-reactivity.On (001) of 1 the hydroxyl groups occur with their hydrogens up.Hence no AFM features are found and crystals of 2 do not become adhered to 1.However, on (100) the hydroxyl hydrogens point down (free electron pair up).Protonation is possible, chemical reaction is indicated by the formation of the AFM features and crystals of 2 adhere firmly to the surface of 1 after reaction.
- Kaupp, Gerd,Haak, Michael,Toda, Fumio
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Read Online
- Solvent-washable polymer templated synthesis of mesoporous materials and solid-acid nanocatalysts in one-pot
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We report a new and simple one-pot synthetic method to produce mesoporous silica and nanoporous solid acid catalyst capable of catalyzing pinacole-pinacolone rearrangement and esterification reactions, by preparing a solvent washable phosphonated triblock copolymer template and self-assembling it in the presence of alkoxysilane.
- Mishler Ii, Richard E.,Biradar, Ankush V.,Duncan, Cole T.,Schiff, Eric A.,Asefa, Tewodros
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Read Online
- Method for preparing substituted carbonyl compound by catalyzing pinacol rearrangement reaction through molecular sieve
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The invention discloses a method for preparing a substituted carbonyl compound by catalyzing pinacol rearrangement reaction through a molecular sieve. The method is characterized in that substituted pinacol as a substrate and toluene as solvent are subjected to a rearrangement reaction for 2-5h under the catalysis of an MCM-41, SBA-15, USY, Beta ZSM-5 or other aluminum-containing H-type acidic molecular sieve, the reaction temperature is 80-110 DEG C, the mass ratio of the substituted pinacol to the toluene to the catalyst is 100: 100: (10-50), the catalyst is filtered out after the reaction is finished, and purifying is performed to obtain a product, namely, the substituted carbonyl compound. Compared with the prior art, the method provided by the invention has the advantages of wide substrate application range, cheap catalyst, easy preparation, stability, no pollution to the environment, recyclability, realization of gram-scale preparation, and high reaction yield.
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Paragraph 0021-0026
(2020/09/12)
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- 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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- Lewis Acid Assisted Electrophilic Fluorine-Catalyzed Pinacol Rearrangement of Hydrobenzoin Substrates: One-Pot Synthesis of (±)-Latifine and (±)-Cherylline
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A microwave-irradiated solvent-free pinacol rearrangement of hydrobenzoin substrates catalyzed by a combination of N-fluorobenzenesulfonimide and FeCl3·6H2O was developed. Its selectivity was first investigated by density functional theory (DFT) calculations. Then the functional group tolerance was examined by synthesizing a series of substrates designed based on the insight provided by the DFT calculations. The application of the methodology was demonstrated by the efficient one-pot synthesis of (±)-latifine and (±)-cherylline, both are 4-aryltetrahydroisoquinoline alkaloids isolated from Amaryllidacecae plants.
- Shi, Hui,Du, Chuan,Zhang, Xinhang,Xie, Fukai,Wang, Xiaoyu,Cui, Shanshan,Peng, Xiaoshi,Cheng, Maosheng,Lin, Bin,Liu, Yongxiang
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p. 1312 - 1319
(2018/02/09)
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- Pinacol Rearrangement and Direct Nucleophilic Substitution of Allylic Alcohols Promoted by Graphene Oxide and Graphene Oxide CO2H
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Graphene oxide (GO) and carboxylic acid functionalized GO (GO–CO2H) have been found to efficiently promote the heterogeneous and environmentally friendly pinacol rearrangement of 1,2-diols and the direct nucleophilic substitution of allylic alcohols. In general, high yields and regioselectivities are obtained in both reactions using 20 wt % of catalyst loading and mild reaction conditions.
- Gómez-Martínez, Melania,Baeza, Alejandro,Alonso, Diego A.
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p. 1032 - 1039
(2017/03/27)
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- Tetraarylethylenes from Diarylmethanones and Hexachlorodisilane: The “Sila-McMurry” Reaction
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Hexachlorodisilane reacts with diarylmethanones (aryl=C6H5, 4-MeC6H4, 4-tBuC6H4, 4-ClC6H4, 4-BrC6H4) to furnish the corresponding tetraarylethylenes in good yields. The reductive conversion requires temperatures of about 160 °C and reaction times of 60–72 h. In the initial step, the Lewis-basic carbonyl groups likely generate low-valent [SiCl2] as an analogue of [TiCl2] in the classical McMurry reaction. The coupling sequence further proceeds via benzopinacolones, which have been isolated as key intermediates.
- Moxter, Maximilian,Tillmann, Jan,Füser, Matthias,Bolte, Michael,Lerner, Hans-Wolfram,Wagner, Matthias
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supporting information
p. 16028 - 16031
(2016/10/26)
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- New insights into the bifunctionality of vanadium phosphorous oxides: A chemical switch between oxidative scission and pinacol rearrangement of vicinal diols
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New insights into the bifunctionality of vanadium phosphorus oxides (VPOs) were obtained. This study reports the precise tuning of experimental conditions, which act as the switch to direct the course of reaction selectively to obtain either CC oxidative scission or an acid-catalysed rearrangement of vicinal diols. The catalyst was synthesized and characterized to identify the active vanadyl pyrophosphate phase. The present method was extended further to develop a new environmentally benign and green catalytic protocol for oxidative cleavage of a variety of vicinal diols with 100% selectivity towards the corresponding aldehydes or ketones using H2O2 as the oxidizing agent.
- Upadhyaya, Dharita J.,Samant, Shriniwas D.
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- o-benzenedisulfonimide as reusable bronsted acid catalyst for acid-catalyzed organic reactions
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Acid-catalyzed organic reactions, such as etherification, esterification, acetal synthesis, cleavage, and interconversion, and pinacol rearrangement were carried out in the presence of catalytic amounts of o-benzenedisulfonimide as Bronsted acid catalyst; the conditions were mild and selective. The catalyst was easily recovered and purified, ready to be used in further reactions, with economic and ecological advantages. Georg Thieme Verlag Stuttgart.
- Barbero, Margherita,Cadamuro, Silvano,Dughera, Stefano,Venturello, Paolo
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p. 1379 - 1388
(2008/12/21)
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- SiCl4-Zn induced reductive coupling of carbonyl compounds: novel and efficient routes for one-pot syntheses of 1,2,3-triaryl-2-propen-1-ones and pinacolones at room temperature
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An unprecedented one-pot reductive trimerization of aromatic aldehydes to 1,2,3-triaryl-2-propen-1-ones as well as tandem reductive coupling-rearrangements of aryl ketones to pinacolone analogues was efficiently achieved using tetrachlorosilane-zinc at room temperature.
- Salama, Tarek A.,Elmorsy, Saad S.,Khalil, Abdel-Galel M.
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p. 4395 - 4398
(2008/02/03)
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- BF3·2CF3CH2OH (BF 3·2TFE), an efficient superacidic catalyst for some organic synthetic transformations
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BF3 · 2CF3CH2OH complex was found to be a very effective superacidic catalyst comparable in acid strength to at least that of 100% anhydrous sulfuric acid for various acid-catalyzed organic transformations such as isomerizations, rearrangements, ionic hydrogenation of various ketones, and aromatics with triethylsilane and nitration of aromatics with metal nitrate. Studies of the pivalaldehyde-methyl isopropyl ketone rearrangement and the benzopinacol to phenanthrene transformation suggest that the complex has an acidity comparable to that of 100% anhydrous sulfuric acid. The structure and properties of the 1:2 boron trifluoride-trifluoroethanol complex have been further studied using NMR (1H, 13C, 19F, 11B) and DFT calculations at the B3LYP/6- 311++G**//B3LYP/6-31G* level.
- Prakash, G. K. Surya,Mathew, Thomas,Marinez, Eric R.,Esteves, Pierre M.,Rasul, Golam,Olah, George A.
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p. 3952 - 3958
(2007/10/03)
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- Aminium hexachloroantimonate salts as latent sources of antimony pentachloride in pinacolic rearrangement of vicinal diols
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Rearrangements of various vicinal diols (1a-f) induced by hexachloroantimonate aminium salts A or B were found to occur in a similar manner when antimony pentachloride was used instead of aminium salts. Antimony pentachloride is proposed as the active catalytic species, possibly deriving from the oxidation of the hexachloroantimonate anion Sbcl6 - by the aminium counterpart. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005.
- Ciminale, Francesco,Lopez, Luigi,Nacci, Angelo,D'Accolti, Lucia,Vitale, Floriana
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p. 1597 - 1603
(2007/10/03)
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- Pinacol-Pinacolone Rearrangement on FeCl3 Modified Montmorillonite K10
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Pinacol-pinacolone rearrangement was investigated over Fe-modified montmorillonite K10 catalysts in liquid phase. Exceptional activity was found to be associated with FeCl3 impregnated on K10 through its acetonitrile solution. 100% conversion of benzopinacol was observed in 10 minutes. The catalysts are recyclable.
- Shinde, Ajit B.,Shrigadi, Nilesh B.,Bhat, Ramakrishna P.,Samant, Shriniwas D.
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p. 309 - 314
(2007/10/03)
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- Reactions of aniline with alkali metal diphenylketyls and dianions derived from benzophenone and Michler's ketone
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Potassium diphenylketyl and benzophenone dianion react with aniline to afford N-(diphenylmethylene) aniline. Under analogous conditions, the corresponding sodium and lithium derivatives undergo disproportionation with formation of triphenylmethanol, benzo
- Turaeva,Kurbatov
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p. 1787 - 1790
(2007/10/03)
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- 4,4,6-Trimethyl-2-vinyl-1,3,2-dioxaborinane: A superior 2-carbon building block for vinylboronate Heck couplings
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4,4,6-Trimethyl-2-vinyl-1,3,2-dioxaborinane is a superior reagent in terms of stability and reactivity in comparison to the vinylboronate pinacol ester, giving improved selectivity for Heck versus Suzuki coupling with both aryl iodides and bromides, and being easier to prepare and store.
- Lightfoot, Andrew P.,Maw, Graham,Thirsk, Carl,Twiddle, Steven J. R.,Whiting, Andrew
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p. 7645 - 7648
(2007/10/03)
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- Method for preparing chiral diphosphines
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The invention concerns a method for preparing a compound of formula (1) wherein: A represents naphthyl or phenyl optionally substituted; and Ar1, Ar2independently represent a saturated or aromatic carbocyclic group, optionally substituted.
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- Pinacol reduction-cum-rearrangement. A re-examination of the reduction of aryl alkyl ketones by zinc-aluminum chloride
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Reduction of alkyl phenyl ketones by zinc and aluminum chloride in acetonitrile results in pinacol condensation followed by rearrangement. The phenyl group migrates in every instance.
- Grant, Anya A.,Allukian, Myron,Fry, Albert J.
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p. 4391 - 4393
(2007/10/03)
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- Novel bronsted acidic ionic liquids and their use as dual solvent-catalysts
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The reaction of triphenylphosphine or N-butylimidazole with cyclic sultones gives zwitterions that are subsequently converted into ionic liquids by reaction with trifluoromethane sulfonic acid or p-toluenesulfonic acid. The resulting ionic liquids have cations to which are tethered alkane sulfonic acid groups. These Bronsted acidic ionic liquids are useful solvent/catalysts for several organic reactions, including Fischer esterification, alcohol dehydrodimerization and the pinacol rearrangement. The new ionic liquids combine the low volatility and ease of separation from product normally associated with solid acid catalysts, with the higher activity and yields normally found using conventional liquid acids. Copyright
- Cole, Amanda C.,Jensen, Jessica L.,Ntai, Ioanna,Tran, Kim Loan T.,Weaver, Kristin J.,Forbes, David C.,Davis Jr., James H.
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p. 5962 - 5963
(2007/10/03)
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- Ozonation of 1,1,2,2-tetraphenylethene revisited: Evidence for electron- transfer oxygenations
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Ozonolyses of 1,1,2,2-tetraphenylethene (TPE, 1) have been described many times in the literature, but the reports are contradictory. This reaction is particularly important for understanding the mechanism of alkene ozonolysis, in view of possible stabilization of reactive intermediates by aryl groups. Thus, systematic investigations of ozonolysis in both aprotic solvents and in protic solvents are reported here. Attention is directed to the following details that have been underestimated in the past: i) the actual electronic structure of ground-state ozone (O3), ii) differentiation between strained and unstrained alkenes, iii) the significance of both the O3 concentration and the TPE concentration, iv) the influence of various solvents, including pyridine, v) the influence of the reaction temperature, vi) the role of electron-transfer catalysis (ETC) and, yii) the effect of structural modifications. Our results suggest that ozonolysis of TPE (1) does not include a 1,3-dipolar reaction step, but represents a particularly interesting example of electron-donor (TPE)/electron-acceptor (O3) redox chemistry. The present investigations include several crucial results. First, pure 3,3,6,6-tetraphenyltetroxane (3, m.p. 221°(dec.)) and pure tetraphenylethylene ozonide (4, m.p. 153°(dec.)) are prepared for the first time, although 3 and 4 have long been known. Second, the singlet diradical character of O3, lessened by means of hypervalent-electron interaction and predicted by different calculations, is evidenced via reaction with the spintrap galvinoxyl (2,6-bis(1-1-dimethylethyl)-4-{[3,5-bis(1,1- dimethylethyl)-4-oxocyclohexa-2,5-dien-1-ylidene]methyl}phenoxy; 8), and the zwitterionic reaction behavior of ground-state O3 is ruled out. Third, the electronacceptor ability of O3 is evidenced by reactions with suitable tetraaryl ethylenes: it is enhanced by addition of catalytic amounts of protons or Lewis acids. Fourth, the observed distribution of the O3 O-atoms to the two different olefinic C-atoms of the unsymmetric alkene 27b is in full agreement with an initial single-electron transfer (SET) step, followed by a radical mono-oxygenation to cause the crucial C,C cleavage. Final dioxygenation should lead to the generally known products (ozonides, tetroxanes, hydroperoxides). The regioselectivity is found to be inconsistent with the expected decay of an intermediate primary ozonide. Finally, the treatment of 1,2-bis(4-methoxyphenyl)acenaphthylene (36) with O3 (simultaneous transfer of three O-atoms) leads to the same experimental result as a stepwise transfer of one O-atom followed by a transfer of two O- atoms.
- Schank, Kurt,Beck, Horst,Buschlinger, Michael,Eder, Joerg,Heisel, Thomas,Pistorius, Susanne,Wagner, Christiane
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p. 801 - 826
(2007/10/03)
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- Acid catalysis vs. electron-transfer catalysis via organic cations or cation-radicals as the reactive intermediate. Are these distinctive mechanisms?
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Proton transfer to aromatic and olefinic donors (D) leads to the facile interchange of transient carbocations (DH+) and cation-radical (D+.). The same types of cation and cation-radical are reactive intermediates in the acid catalysis and the electron-transfer catalysis of such organic transformations as benzylic coupling, epoxide/pinacol rearrangements and cis-trans isomerization of stilbenes when they are both carried out under otherwise identical reaction conditions. However, the rapid exchange of diamagnetic cations and paramagnetic cation-radicals blurs the traditional view of separate electrophilic and homolytic processes, and rigorous experimental evidence is required to establish whether acid catalysis and electron-transfer catalysis actually represent distinct mechanistic categories. Acta Chemica Scandinavica 1998.
- Rathore, Rajendra,Kochi, Jay K.
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p. 114 - 130
(2007/10/03)
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- Preparation of Condensed Aromatics by Superacidic Dehydrative Cyclization of Arvl Pinacols and Eooxides
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Aryl pinacols and epoxides, respectively, are cleanly and in high yield converted via superacidic dehydrative cyclization to the corresponding condensed aromatics. Dehydrative cyclization of benzopinacol (1a), triphenylacetophenone (2), and tetraphenylethylene oxide (9) give 9,10-diphenylphenanthrene (3a) as the major product in acidic media stronger than Ho = -11. Aryl pinacol 12a forms the condensed aromatic 13a as the major product in acidic media stronger than Ho = -13.5. It is proposed that the dehydrative cyclizations to provide aromatics 3a and 13a occurs through dicationic intermediates. Substituted benzopinacols 1f, 1g, and 1j are prepared and give the corresponding phenanthrenes (3f, 3g, and 3j) in high yields. The regiochemistry of the cyclization of substituted benzopinacols is controlled by deactivating substituents on the aryl rings. Aryl pinacols (12a-d) derived from acenaphthenequinone and pinacol 15 also give condensed aromatics (13a-d and 16, repectively) with superacidic triflic acid.
- Klumpp, Douglas A.,Baek, Donald N.,Prakash, G.K. Surya,Olah, George A.
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p. 6666 - 6671
(2007/10/03)
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- Proximity, photochemical reactivity, and intermolecular 1H-13C cross polarization in benzophenone-d10 and cyclohexane in the zeolite NaX
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The photochemistry, photophysics, and solid-state 13C CPMAS NMR of benzophenone and cyclohexane in the zeolite NaX have been analyzed to investigate their proximity, relative mobility, and intermolecular reactivity. Photochemical irradiation of benzophenone in pure cyclohexane yields benzopinacol and benzhydrol as the predominant products. In contrast, irradiation in the solid state leads to 1-cyclohexyl-1,1-diphenylmethanol as the only product by collapse of the radical pair formed after hydrogen abstraction from cyclohexane by excited benzophenone. Phosphorescence analysis at 77 K suggests a highly polar environment, but lack of emission at 300 K in the presence of cyclohexane is assigned to triplet decay via an efficient hydrogen abstraction reaction. Spectral analysis by 13C CPMAS NMR reveals that benzophenone and cyclohexane are adsorbed in an approximate 1:2 ratio. Changes observed in spinning and static samples before and after photolysis are interpreted in terms of molecular motions that are capable of affecting the spectral line width. That benzophenone and cyclohexane share the zeolite supercages in a close packed arrangement was shown by a relatively efficient 1H-13C intermolecular cross polarization from cyclohexane to benzophenone-d10. Comparison of the CPMAS intensities measured with deuterated and nondeuterated benzophenone samples under identical conditions suggest that intermolecular C-D···H-R distances between carbon atoms of deuterated benzophenone and hydrogens of cyclohexane have an average value of ca. 2.2 A?.
- Cizmeciyan, Deniz,Sonnichsen, Laura B.,Garcia-Garibay, Miguel A.
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p. 184 - 188
(2007/10/03)
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- Reactions of pinacols with one-electron oxidants
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Oxidation of the tetraarylpinacols (Ar2COH)2, 1a-e, in which Ar = C6H5 (1a), 4-ClC6H4 (1b), 4-MeC6H4 (1c), 4-MeOC6H4 (1d) and 4-Me2NC6H4 (1e), by thianthrene cation radical (Th?+) in CH3-CN and in CH2Cl2 led quantitatively to the corresponding diaryl ketones Ar2C=O (2a-e), provided a sufficient amount of base, 2,6-di-tert-butyl-4-methylpyridine (DTBMP), was present to prevent presumed acid-catalyzed rearrangement. In the case of 1e, continued oxidation of 2e was also observed. Oxidation of 1a by (4-BrC6H4)3N?+SbCl 6- and (4-BrC6H4)3N?+SbF 6- (Ar3N?+) occurred analogously. Evidence for the catalytic, cation-radical rearrangement of 1a by Ar3N?+ (reported in earlier literature) and by Th?+ could not be found. Quantitative oxidation of 1a to 2a and of 1d to 2d was obtained also with NOBF4, again provided that sufficient DTBMP was present to prevent acid-catalyzed rearrangement. Catalytic, oxidative rearrangement of 1d at room temperature and (as reported in earlier literature) at -5 °C was not observed. Oxidation was also observed of 2,3-diphenyl-2,3-butanediol (3) to acetophenone (9) and of 1,1-dimethyl-2,2-diphenylethanediol (4) to 2a and acetone by Th?+. Oxidation of 2,3-dimethyl-2,3-butanediol (5) by Th?+ was not observed. Instead, even in the presence of DTBMP, pinacolone (10) and tetramethyloxirane (11) were formed, through, it is proposed, a mechanism involving complexation with Th?+.
- Han, Dong Sul,Shine, Henry J.
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p. 3977 - 3982
(2007/10/03)
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- Catalytic epoxidation of hindered olefins with dioxygen. Fast oxygen atom transfer to olefin cation radicals from nitrogen oxides
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Hindered olefins are efficiently converted to epoxides by dioxygen at 25°C in dichloromethane containing catalytic amounts of nitrogen oxides (NO2, NO+, NO, etc.). Nitrogen dioxide also effects the direct (stoichiometric) epoxidation of the same hindered olefins. Olefin cation radicals are spectrally identified as the first observable intermediate, and separate experiments confirm the facile transfer of an oxygen atom from nitrogen dioxide to olefin cation radicals to produce epoxides. At low temperature (-78°C), the epoxidation is rapidly initiated by added 1-electron oxidants such as tris(2,4-dibromophenyl)amine cation radical and nitrosonium (NO+). Scheme 3 presents the complete sequence of redox changes that are mediated by the nitrogen oxides in the catalytic conversion of hindered olefins to epoxides via the cation radical. The deliberate irradiation of the charge-transfer absorption band of the corresponding olefin electron donor-acceptor complexes with tetranitromethane also establishes the formation of epoxides to occur via the same reactive pair, i.e., the olefin cation radical and NO2. The mechanistic implication of rapid oxygen atom transfer to olefin cation radicals is underscored in the general consideration of catalytic epoxidations with dioxygen.
- Bosch, Eric,Kochi, Jay K.
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p. 1319 - 1329
(2007/10/03)
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- AFM in organic solid state reactions
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Organic solid-state reactions are probed with the atomic force microscope (AFM). In all cases phase rebuilding gives rise to characteristic submicroscopic features which change in shape due to phase transformation in later stages of the chemical reaction. Photo-(E/Z)-isomerization of olefin 1 occurs in the crystal, photodimerization of 9-chloroanthracene 3 is used as a probe for characterizing the luminosity distribution of SNOM-tips. Gas/solid imbibition in chiral host 5 proceeds enantiospecifically. Histidine crystals form the dihydrochloride with HCl, ammonia and methylamine react face-selectively with crystalline adipic acid 8, furane-2-carboxylic acid 10 and 2-mercaptobenzothiazole 12. Crystals of olefin 14 add chlorine. Solid-state diazotations and subsequent transformations of the solid diazonium nitrates into triazenes occur quantitatively. Solid/solid pinacol- and benzilic acid rearrangements are probed with the AFM. The features formed by long range molecular movements relate to the crystal packing and are thus different on different faces. Correlations with X-ray structural data are demonstrated. All reactions proceed to completion on a preparative scale and do not produce wastes as do their less selective counterparts if performed in solution. Organic solid-state reactions, AFM, SNOM-tip, imbibition, salt formations, chlorination, diazotations, triazene, gas/solid-reactions, solid/solid-reactions, crystal packing, waste-free reactions.
- Kaupp, Gerd,Schmeyers, Jens,Haak, Michael,Marquardt, Thorsten,Herrmann, Andreas
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p. 315 - 317
(2007/10/03)
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- Synthesis of 2-Cyano-1,1,2,2-tetraphenylethyl Cation and Silver Ion Assisted Solvolysis of sym-Tetraphenylethylene Dichloride
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The reaction of 3-chloro-2,2,3,3-tetraphenylpropanenitrile (2) with AgSbF6 or SbCl5 below -55 deg C in methylene chloride produces the stable, long-lived cation 2-cyano-1,1,2,2-tetraphenylethyl cation (5).Treatment of 5 with TMSCN affords a 98percent yield of 2,2,3,3-tetraphenylsuccinonitrile.It was also found that cation 5 generated with AlCl3 at 0 deg C can undergo intramolecular aromatic substitution to give 9-(cyanodiphenylmethyl)fluorene (8).In the reactions of sym-tetraphenylethylene dichloride (1) with CF3COOAg in the presence of methanol, it was found that tetraphenylethanone dimethyl ketal (9) can be synthesized in 91percent yield.Because rearrangement occured, 1-methoxy-1,2,2,2-tetraphenylethyl cation (15) is proposed as a reaction intermediate.In contrast, treatment of dichloride 1 with CF3CO2Ag in the presence of phenol or isopropyl or allyl alcohol did not produce the corresponding ketals but the 1,3-dioxolane ortho esters 19, 20, or 21 (2-alkoxy-2-trifluoromethyl)-4,4,5,5-tetraphenyl-1,3-dioxolanes).
- Wo, Shiming,Zieger, Herman E.,Millar, Michelle M.,Koch, Stephen A.
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p. 5925 - 5930
(2007/10/03)
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- REACTIONS ON VICINAL DIOLS INDUCED BY AMINIUM SALTS. PROTIC-ACID- OR RADICAL-CATION-CATALYZED PROCESSES
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Vicinal diols by reaction with aminium salts lead, in strongly acidic media, to reaction products, which might arise from a chain electron-transfer mechanism, or through the intermediate formation of a β-hydroxy carbocation.
- Lopez, Luigi,Mele, Giuseppe
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p. 403 - 408
(2007/10/02)
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- Pinacol-Pinacolone Rearrangement Induced By Aminium Salts
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Catalytic amounts of aminium salts induce a quantitative and mild pinacol-pinacolone rearrangement of several vicinol diols in methylene dichloride solutions.
- Lopez, Luigi,Mele, Giuseppe,Mazzeo, Costanza
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p. 779 - 782
(2007/10/02)
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- Aerobic Epoxidation of Hindered Olefins and Enol Ethers Catalyzed by a Polymerizable β-Ketoesterate Complex of Iron(III).
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Peculiar hindered olefins and derivatives have been epoxidized, under Mukaiyama's conditions, using iron(II) catalytic centres.The experimental results allow to rule out the involvement of singlet oxygen and free peroxyacids as active species.
- Lopez, Luigi,Mastrorilli, Piero,Mele, Guiseppe,Nobile, Cosimo F.
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p. 3633 - 3636
(2007/10/02)
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- "Site Selective" Formation of Low-Valent Titanium Reagents: An "Instant" Procedure for the Reductive Coupling of Oxo Amides to Indoles
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Aromatic acylamido carbonyl compounds are readily cyclized to indole derivatives upon treatment with low-valent titanium reagents of the formal oxidation states 0, +1, and +2.Other strong reducing agents such as SmI2 and low-valent zirconium, niobium, and tungsten complexes are also capable of effecting such intramolecular alkylidenation reactions of amides.From the preparative point of view these heterocycle syntheses are best effected with an active titanium species which is prepared in the presence of the carbonyl compound upon coordination of TiCln (n = 3, 4) to the oxo amide substrate and reduction of this complex with zinc dust ("instant" method).This procedure turned out to be as effective as the titanium-graphite-based methodology previously described but is much easier to perform as all hazardous reagents are avoided. "Instant" cyclizations can also be run in nonetheral solvents such as DMF, ethyl acetate, or acetonitrile and turned out to be compatible with many functional groups.The method was used to cyclize oxo amide 15 to (+)-aristoteline, and it applies nicely to the synthesis of strained indole derivatives, the formation of benzofurans, conventional McMurry reactions of aldehydes and ketones, and the dimerization of alkynes.Metals such as zirconium can also be activated in situ by reduction of ZrCl4 in the presence of a carbonyl compound.On the basis of the results obtained with substrates bearing appropriate structural probes a mechanism for such intramolecular keto-amide coupling processes is proposed.Carbonyl dianions, formed upon two-electron reduction of the keto group, are the most likely reactive intermediates.Electrochemical investigations support this mechanistic interpretation.
- Fuerstner, Alois,Hupperts, Achim,Ptock, Arne,Janssen, Edo
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p. 5215 - 5229
(2007/10/02)
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- N-Fluorobisimides: Reactions with Some Olefins via α-Fluoro Carbocationic Intermediates
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N-Fluorobisimides are a new class of electrophilic fluorinating agents.Reaction of (CF3SO2)2NF (1) with olefins gave various products, depending on the reaction conditions and the structure of the substrate.In solvents of higher nucleophilicity such as H2O, acetic acid, aqueous HCl, and (HF)nPy, α-fluorohydrins and their acetates, α,β-chlorofluoro- and α,β-difluoroalkanes were obtained.In acetic acid, trans-stilbene and tetraphenylethylene produced the rearranged, nonfluorinated aldehyde and ketone.Evidence is presented for the reactions proceeding via a one-electron transfer mechanism involving α-fluorocarbocationic intermediates.
- DesMarteau, Darryl D.,Xu, Ze-Qi,Witz, Michael
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p. 629 - 635
(2007/10/02)
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- TELLURIUM TETRACHLORIDE AS A MILD DEPROTECTION REAGENT FOR ACETALS AND THIOACETALS
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On treatment with tellurium tetrachloride in dichloromethane at room temperature, acetals and thioacetals are easily cleaved to regenerate original carbonyl compounds in good yields.
- Tani, Hiroyuki,Inamasu, Tokuo,Masumoto, Kazunori,Tamura, Rui,Shimizu, Hiroshi,Suzuki, Hitomi
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p. 261 - 266
(2007/10/02)
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- The Catalytic Pinacol Rearrangement of 1,2-Diols Using an Antimony(V)Salt
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In the presence of a catalytic amount of antimony(V)chloride or antimony(V)salt generated from antimony(V)chloride and silver hexafluoroantimonate, the pinacol rearrangement of several 1,2-diols or their trimethylsilyl ethers proceeds smoothly to give the corresponding ketones in good yields.
- Harada, Tsunehiro,Mukaiyama, Teruaki
-
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- Facile reductive dimerisation of aryl ketones using Zn-Ac2O
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A simple reductive dimerisation of aryl ketones by zinc-acetic anhydride, resulting in the formation of pinacolones and related compounds is reported.
- Nair, C. K. Snehalatha,Krishnakumari, B.,Pardhasaradhi, M.
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p. 540 - 542
(2007/10/02)
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- Zinc-Promoted Reactions. 1. Mechanism of the Clemmensen Reaction. Reduction of Benzophenone in Glacial Acetic Acid
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The mechanism of the Clemmensen reduction of diaryl ketones was investigated by reducing benzophenone, benzhydryl chloride, and dichlorodiphenylmethane in AcOH under a variety of conditions.Besides diphenylmethane, dimeric products were isolated that were indicative of the formation of radical species.Different product distributions were obtained from reactions run under different conditions.The reduction of deuteriated benzhydryl chloride was also performed.A quite complicated mechanistic pattern, involving ionic and nonionic reactions, emerged from the experimental p icture.Two pathways, connected through the protonated substrate, were recognized.According to the first pathway the reduction is promoted by a SET from Zn to the substrate, leading to the formation of a carbon radical having one zinc atom bound to the oxygen of the carbonyl group.Benzhydryl chloride, benzhydryl acetate, and dichlorodiphenylmethane are involved in the process.The product distributions suggest the occurrence of several SETs, which involve the formation of different radical species.Ionic reactions are responsible for the second route to the reduced products.Nucleophilic displacements also participate to the complex mechanism.
- Vona, Maria Luisa Di,Rosnati, Vittorio
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p. 4269 - 4273
(2007/10/02)
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- High Catalytic Activities of Pseudoliquid Phase of Dodecatungstophosphoric Acid for Reactions of Polar Molecules
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A solid H3PW12O40 exhibited very high catalytic activities for the reations of polar molecules in the liqiud phase, while it was much less active for the reactions of nonpolar molecules.It was confirmed that the pseudoliquid phase behavior of H3PW12O40 is responsible for the high activities.
- Nishimura, Toru,Okuhara, Toshio,Misono, Makoto
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p. 1695 - 1698
(2007/10/02)
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- SINGLE ELECTRON TRANSFERS IN ZINC-PROMOTED REACTIONS. THE MECHANISMS OF THE CLEMMENSEN REDUCTION AND RELATED REACTIONS.
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A parallel study of the Clemmensen reaction of benzophenone, 1, benzhydryl chloride, 2, and dichlorodiphenylmethane, 3, suggests new hypotheses about the mechanism of this reduction of diarylketones.Two main pathways have been recognized, both involving ionic and non-ionic reactions.The devised mechanisms provide a tool for interpreting literature data not understood hitherto, concerning Clemmensen-type as well as other zinc-promoted reactions.
- Vona, M. L. Di,Floris, B.,Luchetti, L.,Rosnati, V.
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p. 6081 - 6084
(2007/10/02)
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- Novel reductive couplinog-rearrangement of carbonyl compounds with metal/Lewis acid under irradiation of ultrasonic wave
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Novel reductive coupling-rearrangement of carbonyl compounds such as benzophenones with Al or Zn/ AlCl3 in CH3CN under irradiation of ultrasonic wave gave benzopinacolones via epoxides in good yields.
- Sato, Ryu,Nagaoka, Takeshi,Saito, Minoru
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p. 4165 - 4168
(2007/10/02)
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- ELECTRON-TRANSFER CHAIN ISOMERIZATION OF EPOXIDES INDUCED BY ONE-ELECTRON OXIDIZING AGENTS
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One electron oxidizing agents have been employed to achieve the isomerization of epoxides to ketones.The reactions most likely proceed via a radical cation chain electron-transfer mechanism.
- Lopez, Luigi,Troisi, Luigino
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p. 3097 - 3100
(2007/10/02)
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- Pinacol-Pinacolone Rearrangement Promoted by Polyphosphoric Acid Trimethylsilyl Ester (PPSE)
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Pinacols afforded the corresponding pinacolones in high yields in the presence of the polyphosphoric acid trimethylsilyl ester (PPSE) at a temperature above 80 deg C.Tetraphenylethylene oxide, in addition to benzopinacolone, was obtained in the reaction of benzopinacol under milder conditions.The solvent effect suggested that the rearrangement proceeded via the carbonium-ion intermediate.
- Kakimoto, Masa-aki,Seri, Takuya,Imai, Yoshio
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p. 2643 - 2644
(2007/10/02)
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- PINACOL CLEAVAGE USING IRON(III)TRISPHENANTHROLINE COMPLEXES
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Oxidative bond cleavage of benzpinacol and 2,3-diphenyl-2,3-butanediol have been effected with two Fe(III)(1,10-phenantroline)3 complexes which are thought to undergo electron transfer reactions by an outer sphere mechanism.The products of these reactions are exclusively the corresponding ketones when 2,6-di-t-butylpyridine is added to the solution.In contrast to the facile oxidations of these aromatic substrates, pinacol is not cleaved under these reaction conditions.
- Penn, John H.,Deng, Dao-Li,Chai, Kyung-Jin
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p. 3635 - 3638
(2007/10/02)
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- REACTION OF CHLOROSULFONYL ISOCYANATE WITH 1,2-DIOLS: REARRANGEMENT AND FORMATION OF CARBONATES
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1,2-Diols, 1a-e, upon reaction with chlorosulfonyl isocyanate (CSI) gave the ketones, 3a-e.Under similar experimental conditions, 1,2-diols, 1f-k, gave carbonyl compounds, 3f-k, carbonates, 6f-k, carboxamides, 7h,i, and the epoxide, 5i.
- Joseph, Sajan P.,Dhar, D. N.
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p. 2295 - 2302
(2007/10/02)
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- Pentavalent Organobismuth Reagents. Part 3. Phenylation of Enols and of Enolate and other Anions
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The phenylation of enols and of enolate anions of ketones, β-diketones and keto esters has been studied using a range of Bi reagents.Under basic conditions C-phenylation is observed and, even hindered, perphenylated compounds are easily synthesized.Under neutral and acidic conditions ordinary ketones do not react and enolic systems give O-phenylation.A number of other anions have been phenylated under basic conditions, including the key compound indole wich mainly gave 3-C-phenylation.All these reactions can be supposed to have one of two alternative mechanisms, which parallel the two mechanisms proposed for the phenylation of phenols.
- Barton, Derek H. R.,Blazejewski, Jean-Claude,Charpiot, Brigitte,Finet, Jean-Pierre,Motherwell, William B.,et al.
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p. 2667 - 2676
(2007/10/02)
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- The Reaction of Chlorosulfonyl Isocyanate with Epoxides. A Novel Conversion of Epoxides to Cyclic Carbonates
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The facile reaction of chlorosulfonyl isocyanate (CSI) with epoxides is described.The initially formed 2-chlorosulfonylimino-1,3-dioxolane 2a-e and N-chlorosulfonyl-1,3-oxazolidin-2-one 3a-e derivatives undergo smooth hydrolysis to yield the corresponding 1,3-dioxolan-2-one 4a-e and 1,3-oxazolidin-2-one 5a-e derivatives respectively.This reaction sequence provides a convenient one-pot method for the conversion of epoxides to cylic carbonates.Substrates such as 1g-i are exceptions to this otherwise general reaction pathway.
- Keshava Murthy, K. S.,Dhar, D. N.
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p. 1721 - 1725
(2007/10/02)
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- ELECTROGENERATED ACID AS A POWERFUL CATALYST FOR TRANSFORMATION OF EPOXIDES TO KETONES AND ACETONIDES
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Electrochemical Transformation of epoxides 1 to ketones 2 and acetonides 3 were achieved by using an electrogenerated acid-catalyst.A combination of M(ClO4)n with polar aprotic solvents is useful for the electrochemical transformation.
- Uneyama, Kenji,Isimura, Akihiro,Fujii, Kazuyuki,Torii, Sigeru
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p. 2857 - 2860
(2007/10/02)
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- Anodic Behaviour of Epoxides: Conditions for an Electron-transfer Chain Isomerisation induced by the Electrode
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The electrocatalytic isomerisation of epoxides is observed anodically in acetonitrile free from strong nucleophiles; the electrochemically induced isomerisation and the similar isomerisation caused by strong acids are compared.
- Delaunay, Jacques,Lebouc, Alain,Tallec, Andre,Simonet, Jacques
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p. 387 - 388
(2007/10/02)
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- Oxidizing Action of Complex of N,N-Dimethylbenzylamine Oxide with SbCl5
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A 1:1 complex of N,N-dimethylbenzylamine oxide-SbCl5 (1) was prepared in carbon tetrachloride quantitatively.Complex 1 was found to be a better reagent for oxidation of benzoin, furoin, benzyl alchols and pinacols than the complexes pyridine N-oxide-SbCl5 and trimethylamine oxide-SbCl5.The reaction path in oxidation of benzhydrol with 1 is described.
- Yamamoto, Jiro,Tanioka, Yukio,Umezu, Masahiro
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p. 3035 - 3036
(2007/10/02)
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- Derivatives of 1,3,5-Triazine : Part II - Reactions of Cyanuric Chloride, a New Condensing Agent
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Cyanuric chloride, a new condensing agent, has been found to be useful in the preparation of acid chlorides, amides and esters in good yields from carboxylic acids, picryl chloride from picric acid, and in bringing about the pinacol rearrangment of substituted ethanediol derivatives and lactonization of (R)-(+)-ricinelaidic acid.Treatment of cyanuric chloride with ethanol and formamide at room temperature gives triethyl orthoformate in 28percent yield.
- Lahoti, R. J.,Wagle, D. R.
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p. 852 - 855
(2007/10/02)
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- Preparation and Properties of, and Reactions with, Metal-Containing Heterocycles, XI. Preparation and Properties of Ethanediyl-, Propanediyl-, Pentanediyl-, and Decanediyl Bis(trifluoromethanesulfonate)
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The alkanediyl bis(trifluoromethanesulfonates) CF3SO2OCH2-n-CH2OO2SCF3 (1, 2, 2', 3, 4) are obtained from the diols HOCH2-n-CH2OH with (CF3SO2)2O in the presence of pyridine , and from tetrahydro-2H-pyran with (CF3SO2)2O , respectively.The instability of 2 can be traced back to a dipolar interaction between the protons and the CF3SO3- residues attached to the 1,3-carbon atoms.
- Lindner, Ekkehard,Au, Guenter von,Eberle, Hans-Juergen
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p. 810 - 813
(2007/10/02)
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