- Lipophilic indole mediated chemoselective α-monobromination of 1,3-dicarbonyl compounds
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A mild and efficient mono-selective bromination of 1,3-dicarbonyl compounds has been developed using lipophilic indole catalysts. Inexpensive and commercially available N-bromosuccinimide (NBS) was used as the brominating reagent. The selectivity was further enhanced when using stoichiometric amount of 3-bromoindole species. Mechanistic studies reveal that the indole catalyst has dual functions in the mono-bromination process.
- Wong, Jonathan,Ke, Zhihai,Yeung, Ying-Yeung
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- Functionalized Carbon Nanostructures Which are Soluble in Hydrocarbons and Method for Preparation
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Carbon nanomaterials functionalized on their surface with ester or amide functionality are made using a technique involving multiple space apart in time or dropwise additions of reactants to the carbon nanomaterials, and are soluble in hydrocarbon liquids.
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Page/Page column 5
(2011/02/18)
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- Halogenation of carbonyl compounds by an ionic liquid, [AcMIm]X, and Ceric Ammonium Nitrate (CAN)
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An ionic liquid, acetylmethylimidazolium halide ([AcMIm]X), in combination with ceric ammonium nitrate promotes halogenations of a wide variety of ketones and 1,3-keto esters at the ?-position. The ionic liquid acts here as reagent as well as reaction medium, and thus the reaction does not require any organic solvent or conventional halogenating agent. The reaction is completely arrested when the radical quencher TEMPO is used. A plausible radical mechanism is also suggested. CSIRO 2007.
- Ranu, Brindaban C.,Adak, Laksmikanta,Banerjee, Subhash
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p. 358 - 362
(2008/02/13)
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- Bromination by means of sodium monobromoisocyanurate (SMBI)
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A variety of aromatic compounds with both activating and deactivating substituents were brominated with sodium monobromoisocyanurate (SMBI) 1, diethyl ether, diethyl ether-methanesulfonic acid, trifluoroacetic acid, or sulfuric acid were employed as solvents. Thus nitrobenzene was conveniently brominated in sulfuric acid, benzene was readily monobrominated in diethyl ether-methanesulfonic acid, and phenol was selectively brominated at the ortho position under mild conditions in refluxing diethyl ether. With substituents that are easily protonated, trifluoroacetic acid may be employed as solvent in the reaction with 1, in contrast NBS was ineffective in trifluoroacetic acid. This renders 1 a superior reagent relative to NBS. In addition to aromatics, alkenes, ketones and esters were also brominated with 1. Diethyl malonate was brominated with 1 and then subjected to a Bingel reaction with NaH to afford the desired methanofullerene in reasonable yield.
- Okada, Yukihiro,Yokozawa, Masanori,Akiba, Miwa,Oishi, Kazuhiko,O-Kawa, Kyoji,Akeboshi, Tomohiro,Kawamura, Yasuo,Inokuma, Seiichi,Nakamura, Yosuke,Nishimura, Jun
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p. 2506 - 2511
(2007/10/03)
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- Synthesis and decarboxylation of Δ2-cephem-4,4-dicarboxylic acids
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Penicillin V was converted in 14 steps into Δ2-cephems having hydrogen at C-3, hydrogen or methyl at C-2, and two methoxycarbonyl, two benzyloxycarbonyl, or one methoxycarbonyl and one benzyloxycarbonyl substituent at C-4. Deprotection of these Δ2-cephem-4,4-dicarboxylic acid esters by alkaline hydrolysis (in the case of methyl esters) or hydrogenolysis (in the case of benzyl esters) led in all cases to rapid decarboxylation of the Δ2-cephem-4,4-dicarboxylic acid or Δ2-cephem-4,4-dicarboxylic acid monoester. With hydrogen at C-2, hydrolysis of the dimethyl ester with 1 equiv of base produced a Δ2-cephem. With 2 equiv of base, and with all compounds having methyl at C-2, hydrolysis or hydrogenolysis afforded 4α-substituted-Δ2-cephems. In contrast, simpler benzyl or methyl acetamidomalonates could be deprotected without difficulty to afford stable malonic acids. Reasons for the differences in ease of decarboxylation were examined using semiempirical (AM1) and ab initio (3-21G) molecular orbital calculations. The decarboxylation barriers of unionized cephem or acetamido malonic acids were found to be high (35-40 kcal mol-1). Although the monoanion of acetamidomalonic acid retained a high barrier, the epimeric monoanions of a Δ2-cephem malonic acid decarboxylated with barriers of only 2 kcal mol-1.
- Wolfe,Ro,Kim,Shi
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p. 1238 - 1258
(2007/10/03)
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- Radical cyclization of allyl α-bromocarboxylates into γ-butyrolactones. Effect of the ester structure on the cyclization
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Allyl dibromoacetate, allyl α-bromopropionate, and allyl phenylbromoacetate undergo cyclization in benzene in the presence of increased concentration of Fe(CO)5 - DMF as the initiating system to give the corresponding bromo-substituted butyrolactones.
- Terent'ev,Vasil'eva,Kuz'mina,Ikonnikov,Orlova,Mysov,Belokon'
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p. 2096 - 2098
(2007/10/03)
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- CHEMISTRY OF NITRO ESTERS XVII. METHOD FOR THE PRODUCTION OF MESOXALIC ESTERS
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A new preparative method was developed for the production of mesoxalic esters from bromomalonic esters and silver nitrate
- Kochergin, P. M.,Titkova, R. M.
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p. 1042 - 1044
(2007/10/02)
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- Electron Ionization and Chemical Ionization Mass Spectra of Pyridinium and Isoquinolinium Ylides
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Electron ionization (EI) spectra and both positive and negative chemical ionization (CI) spectra have been obtained for four isoquinolinium ylides and two pyridinium ylides.Electron transfer reactions dominate the CI mass spectra.The base peak in negative chemical ionization is the ., is relatively more intense than + showing electron transfer to be the main positive ionization process.In the positive ammonia CI spectra, proton transfer to give + is the main ionization process, but electron transfer is also observed.The EI spectra show fragmentations in which the aromatic nitrogen moiety retains the charge and fragmentation is by loss of radicals or small neutral molecules from the side-chains.Radical driven reactions are proposed to explain these spectra.
- Bowen, D. V.,Skett, P. W.,Thorpe, J.,Plunkett, A. O.
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p. 285 - 290
(2007/10/02)
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- Electrolytic α-Bromination of Some α-Substituted Active Methylene Compounds
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Electrolytic α-bromination of methyl α-substituted malonates and methyl α-substituted acetoacetates was accomplished in 73-84percent yields in dichloromethane containing tetraethylammonium bromide as an electrolyte and sodium methoxide as an enolizing reagent.
- Torii, Sigeru,Uneyama, Kenji,Yamasaki, Noritsugu
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p. 819 - 820
(2007/10/02)
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