- Design and synthesis of sulfonated carbons with amphiphilic properties
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A new type of sulfonated carbon material with amphiphilic properties was synthesized by the hydrothermal carbonization of a mixture of furfural-sodium dodecylbenzene sulfonate at 180 °C in an autoclave. The addition of SDBS is necessary for the production of materials with long carbon chains and is possibly used to improve the solubilization of long carbon-chain and steric compounds such as pivalic acid. The resulting material was characterized by N2 adsorption, XPS, 13C NMR, XRD and FTIR. The synthesized material was proven to be a highly efficient solid-acid catalyst in reactions such as the esterification of pivalic acid with alcohols, and catalytic performance much better than that of conventional solid acid catalysts, e.g. Amberlyst-15 and Nafion resin, was observed.
- Jia, Rong,Ren, Jiawen,Liu, Xiaohui,Lu, Guanzhong,Wang, Yanqin
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p. 11195 - 11201
(2014/07/21)
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- Nucleophilic acyl substitutions of anhydrides with protic nucleophiles catalyzed by amphoteric, oxomolybdenum species
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(Chemical Equation Presented) Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride-MoO2Cl2 adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-α-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl2(O2-CBu t)2 between pivalic anhydride and MoO2Cl 2 as the catalyst.
- Chen, Chien-Tien,Kuo, Jen-Huang,Pawar, Vijay D.,Munot, Yogesh S.,Weng, Shieu-Shien,Ku, Cheng-Hsiu,Liu, Cheng-Yuan
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p. 1188 - 1197
(2007/10/03)
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- Hindered ester formation by SN2 azidation of N-acetoxy-N-alkoxyamides and N-alkoxy-N-chloroamides-novel application of HERON rearrangements
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Treatment of N-acetoxy-N-alkoxyamides or N-alkoxy-N-chloroamides with sodium azide in aqueous acetonitrile results in SN2 displacement of chloride and the formation of reactive N-alkoxy-N-azidoamides. The reaction with N-acetoxy-N-benzyloxybenzamide has been studied kinetically (k294 = 2 L mol-1 s-1) and azidation of N-formyloxy-N-methoxyformamide has been modeled computationally at the pBP/DN*//HF/6-31G* level of theory. The anomeric amides N-alkoxy-N-azidoamides decompose intermolecularly and spontaneously to esters and two equivalents of nitrogen. This extremely exothermic process facilitates the formation, in excellent yields, of highly hindered esters.
- Glover, Stephen A.,Mo, Guoning
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p. 1728 - 1739
(2007/10/03)
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- 1-(2,5-dichlorophenyl)-2,2-bis(methylsulfanyl)vinyl esters as highly efficient chemoselective acylating reagents
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1-(2,5-Dichlorophenyl)-2,2-bis(methylsulfanyl)vinyl esters 4f-k were prepared in yields usually greater than 90%, by reacting acyl chlorides with 1-(2,5-dichlorophenyl)-2,2-bis(methylsulfanyl)ethanone enolate. These esters were demonstrated to be excellent chemoselective reagents for the acylation of amines, alcohols, thiols, pyrrole and indole. From all the acylation reactions the dimethyl α-oxo dithioacetal 2d, recyclable for the preparation of esters 4f-k, could be recovered in 90-100% yield.
- Degani,Dughera,Fochi,Serra
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p. 1200 - 1208
(2007/10/03)
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- 'New' catalysts for the ester-interchange reaction: The role of alkali-metal alkoxide clusters in achieving unprecedented reaction rates
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The catalytic effect of alkali-metal tert-butoxide clusters on the rate of ester interchange for several pairs of esters has been determined in nonpolar and weakly polar solvents. Reactivities increase in the order (Li+ + + + +) with the fastest rates reaching 107 catalytic turnovers per hour (TO/h). Ester interchange rates were sensitive to the size of both the transferring OR groups and the ester substituent. Phenyl esters did not exchange with aliphatic esters due to nonstatistical breakdown patterns in the tetrahedral intermediate. A first-order equilibration analysis on the interchange between tert-butyl acetate (tBuAc) and methyl benzoate (MeBz) (5 mol % NaOtBu) indicated enhanced reaction rates as the reaction proceeded. Isolation and quenching (DCl/D2O) of precipitated catalyst points to a mechanism whereby sequential methoxy incorporation into the catalyst cluster increases activity, but eventually precipitates out of solution as a 3:1 OMe:OtBu cluster. The rate law was determined to be k(obs)[MeBz]1[tBuAc]0[NaOtBu](x), where x = 1.2(1), 1.4(1), and 0.85(1) in hexane, ether, and THF, respectively, under conditions where tetrameric catalyst aggregates are expected. Reaction rates were generally observed to be higher in nonpolar solvents (hexane > toluene, ether > THF). Eyring analysis over a 40°C range yielded ΔH(≠) = 10.0(1) kcal mol-1 and ΔS(≠) = -32(3) eu. A Hammett (σ) plot generated with para-substituted methyl benzoates gave ρ +2.35 (R 0.996). These results are interpreted in terms of a catalytic cycle composed of two coupled transesterification reactions with a turnover-limiting addition of a tert-butoxy-containing cluster (tetramer) to methyl benzoate. Catalyst relative reactivities (Cs+ > Rb+ > K+ > Na+ > Li+) are interpreted in terms of competitive electrostatic interactions between the alkali-metal and ground-state and transition-state anions. This analysis predicts the observed linear dependence between log(k(obs)) and l/r(ionic).
- Stanton, Matthew G.
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p. 5981 - 5989
(2007/10/03)
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- Nitrolysis of carboxylic t-butyl and 1-adamantyl esters
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A cheap, less problematic, efficient and selective reagent for the removal of the t-butyl and 1-adamantyl protecting groups from carboxylic esters was found to be commercial 100% HNO3 in CH2Cl2. Incidentally, 1,1- dimethylethyl nitrate and tricyclo[3.3.1.13,7]dec-1-yl (1-adamantyl) nitrate are coproducts in a clean reaction. The procedure is in many ways superior to the method employing CF3COOH.
- Strazzolini, Paolo,Dali'Arche, Maria Grazia,Giumanini, Angelo G.
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p. 9255 - 9258
(2007/10/03)
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- Zinc promoted mild and efficient method for the esterification of acid chlorides with alcohols
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The esterification of variety of acid chlorides with alcohols in the presence of zinc is described. The easy formation of t-butyl and pivaloyl esters are the additional importance of this procedure.
- Yadav,Reddy, Gondi Sudershan,Srinivas, Dale,Himabindu, Konuru
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p. 2337 - 2342
(2007/10/03)
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- A novel, general route to the synthesis of carboxylic acid esters and thiolesters
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Carboxylic acids were conveniently esterified with alcohols and thiols by the use of triphenylphosphine and N-bromo/Iodo succinimide to afford the corresponding esters and thiol esters.
- Sucheta,Reddy,Ravi,Rama Rao
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p. 4415 - 4416
(2007/10/02)
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- A Mild and Efficient Alumina-Promoted Synthesis of t-Butyl Esters
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A wide variety of aliphatic acid chlorides including an optically active one has been efficiently converted to their t-butyl esters under very mild reaction conditions by employing activated alumina as a catalyst.
- Nagasawa, Kazuo,Yoshitake, Shinji,Amiya, Takao,Ito, Keiichi
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p. 2033 - 2040
(2007/10/02)
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- DECARBOXYLATION OF ALKOXYCARBONYLCOBALT CARBONYLS
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Alkoxycarbonylcobalt tetracarbonyls undergo thermal decarboxylation between 25 and 90 deg C yielding up to 67percent CO2/Co atom; the decarboxylation is favoured by ligand excess (CO, PR3, NEt3).
- Bartik, Tamas,Kruemmling, Thomas,Marko, Laszlo,Palyi, Gyula
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p. 307 - 308
(2007/10/02)
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- An Improved and Convenient Synthesis of Esters Using 1,1'-Carbonyldiimidazole and a Reactive Halide
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The esterification of carboxylic acid proceeded easily in a one-pot reaction with 1,1'-carbonyldiimidazole in the presence of a reactive halide under neutral reaction conditions in high yields. Keywords - esterification: 1,1'-carbonyldiimidazole; formylation; tert-butyl ester; imidazolium salt; one-pot reaction
- Kamijo, Tetsuhide,Harada, Hiromu,Iizuka, Kinji
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p. 5044 - 5047
(2007/10/02)
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- Formation of Iodides and Esters from Alcohols and Tributyldiiodophosphorane and Diiodotriphenylphosphorane
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Tributyldiiodophosphorane and diiodotriphenylphosphorane, prepared in situ from the corresponding phosphine and iodine, are generally able to convert primary and secondary alcohols into iodides at room temperature in diethyl ether or benzene containing two equivalents of hexamethylphosphoric triamide.Tertiary alcohols, as gauged by the lack of the reactivity of t-butyl alcohol, are, however, inert to this iodinating agents. 6-Hydroxyhexanoic acid yields a mixture of 6-iodohexanoic acid and 7-heptanolide.The first reagent also promotes facile condensation of secondaryand tertiary alcohols with carboxylic acids to form hindered esters in good yields.The phosphorane derived from tris(dimethylamino)phosphine and iodine, while less effective as an iodinating agent, rapidly converts 6-hydroxyhexanoic acid into 6-iodo-N,N-dimethylhexanamide, and hexanoic and benzoic acids into the corresponding N,N-dimethylamides in excellent yields at room temperature.Treatment of 3β-tosylocholest-5-ene with lithium iodide yields 3β-iodocholest-5-ene, and not 3α-iodocholest-5-ene, as previously reported.
- Haynes, Richard K.,Holden, Malcolm
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p. 517 - 524
(2007/10/02)
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- Esterification of Carboxylic Acids by Alcohols with 2-Chloro-1,3,5-trinitrobenzene as Condensing Agent
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When mixtures of carboxylic acids or their sodium salts and alcohols were treatment with 2-chloro-1,3,5-trinitrobenzene in the presence of pyridine under mild conditions, the corresponding carboxylic esters were formed.The yields and the rates of the ester formation depended on the types of the acids and the alcohols used.
- Takimoto, Seiji,Inanaga, Junji,Katsuki, Tsutomu,Yamaguchi, Masaru
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p. 1470 - 1473
(2007/10/02)
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- Synthesis and Reactions of N-Protected 2-Lithiated Pyrroles and Indoles. The tert-Butoxycarbonyl Substituent as a Protecting Group
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N-(tert-Butoxycarbonyl)pyrrole and N-(tert-butoxycarbonyl)indole have been prepared and lithiated at the 2-position with lithium 2,2,6,6-tetramethylpiperidide and tert-butyllithium, respectively.These lithium reagents react with a variety of electrophiles to give the 2-substituted N-(tert-butoxycarbonyl)pyrroles and N-(tert-butoxycarbonyl)indoles.The N-(tert-butoxycarbonyl) substituent may be removed rapidly and in high yield from the pyrrole derivatives under basic conditions.For the indole derivatives, the protecting group may be removed with either acidic or basic conditions.
- Hasan, Iltifat,Marinelli, Edmund R.,Lin, Li-Ching Chang,Fowler, Frank W.,Levy, Alan B.
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p. 157 - 164
(2007/10/02)
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