- Efficient condensation of carboxylic acids with alcohols catalyzed by fluorous ammonium triflates
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The use of fluorous ammonium salts as metal-free catalysts for the direct condensation of equimolar amounts of carboxylic acids and aliphatic alcohols has been investigated. Esterification reactions were thus conveniently carried out under mild fluorous biphasic conditions, in the presence of 1 mol % of fluorous ammonium triflate and without recourse to any additional water removal technique. Good to excellent ester yields were obtained in the case of primary and secondary aliphatic alcohols. The fluorous salt was easily recovered by simple phase separation and reused at least three times without considerable loss of activity.
- Mercs, László,Pozzi, Gianluca,Quici, Silvio
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p. 3053 - 3056
(2007/10/03)
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- Highly efficient solvent-free condensation of carboxylic acids with alcohols catalysed by zinc perchlorate hexahydrate, Zn(ClO4) 2·6 H2O
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Zinc perchlorate hexahydrate, Zn(ClO4)2· 6 H2O, efficiently catalyses the esterification between nearly equimolar amounts of carboxylic acids and alcohols. The reaction works under solvent-free conditions at relatively low temperatures. Excellent results were obtained with a wide range of substrates.
- Bartoli,Boeglin,Bosco,Locatelli,Massaccesi,Melchiorre,Sambri
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- 4-(Nitro)-diphenylammonium triflate(NDPAT) catalysed esterification of carboxylic acids with alcohols
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4-(Nitro)-diphenylammonium triflate(NDPAT) efficiently catalysed the esterification between equimolar amounts of carboxylic acids and alcohols in good yield under mild reaction conditions.
- Liu, Xuan-Gan,Hu, Wei-Xiao
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p. 564 - 565
(2007/10/03)
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- Novel and efficient method for esterification, amidation between carboxylic acids and equimolar amounts of alcohols, and amines utilizing Me2NSO2Cl and N,N-dimethylamines; Its application to the synthesis of coumaperine, a natural chemopreventive dieneamide
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Various carboxylic esters or amides were prepared in good to excellent yield between carboxylic acids and equimolar amounts of alcohols or amines under very mild conditions (0-45°C; within 3 h) using dimethylsulfamoyl chloride (Me2NSO2Cl; 1) combined with N,N-dimethylamines (Me2NR: 2a; R=Me, 2b; R=Bu). The choice of the sulfamoyl chloride and the amine is crucial for the reaction; that is, sterically uncrowded amines accelerated the present esterification and amidation. This agent had some advantages over methanesulfonyl chloride (3)/amines as for the atom-economy, avoidance of side reactions, and had very high chemoselectivity toward the carboxyl group vs the hydroxyl group; the experiment was performed by the addition of 1 to the mixture of carboxylic acids and alcohols. Application of this method to the synthesis of coumaperine, a chemopreventive natural product, was performed using the present amidation as a key step.
- Wakasugi, Kazunori,Nakamura, Atsushi,Iida, Akira,Nishii, Yoshinori,Nakatani, Nobuji,Fukushima, Shoji,Tanabe, Yoo
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p. 5337 - 5345
(2007/10/03)
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- Simple, Mild, and Practical Esterification, Thioesterification, and Amide Formation Utilizing p-Toluenesulfonyl Chloride and N-Methylimidazole
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We have developed an efficient method for the esterification or thioesterification of equimolar amounts of carboxylic acids and alcohols or thiols using a novel reagent, p-toluenesulfonyl chloride (TsCl) together with N-methylimidazole. The present method is simple, mild, and reactive, uses readily available and economical reagents. The choice of amine is critical for the present method. The amine, N-methylimidazole, has two roles: (i) as an HCl scavenger for the initial smooth generation of mixed anhydrides between carboxylic acids and TsCl and (ii) successive formation of highly reactive ammonium intermediates from mixed anhydrides. This method could be applied to various types of carboxylic acids, alcohols, and thiols: a) several functionalities were tolerated; b) two N-Cbz amino acids were smoothly esterified without racemization; and c) the labile 1β-methylcarbapenem key intermediate and a pyrethroid insecticide, prallethrin, were successfully prepared. The related amide formation between carboxylic acids and primary or secondary amines was also performed. The proposed reaction mechanism involves a novel method for producing the reactive acylammonium intermediates. The production of these intermediates was rationally supported by a careful 1H NMR monitoring study.
- Wakasugi, Kazunori,Iida, Akira,Misaki, Tomonori,Nishii, Yoshinori,Tanabe, Yoo
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p. 1209 - 1214
(2007/10/03)
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- Fluoroalkyldistannoxane Catalysts for Transesterification in Fluorous Biphase Technology
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Novel, practical protocols of transesterification have been advanced with recourse to fluorous biphase technology. The fluoroalkyldistannoxane catalysts enable transesterification in FC-72 solvent to furnish 100% yields of the desired esters by use of reactants ester and alcohol in a 1:1 ratio. The catalysts also work in FC-72/organic solvent system as well as in toluene alone. A number of esters and alcohols bearing various functional groups are employable. The catalysts can be totally recovered and reused. More conveniently, the catalyst solution in FC-72 which is separated from the reaction mixture is directly used for the next reaction.
- Xiang, Jiannan,Orita, Akihiro,Otera, Junzo
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- A practical and green chemical process: Fluoroalkyldistannoxane-catalyzed biphasic transesterification
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There is no need for the recovery of the catalyst in the fluorous biphasic transesterification catalyzed by [{Cl(C6F13CH2CH2)2 SnOSn(C6F13CH2CH2) 2Cl}2] (1; see scheme), which results in quantitative conversions and yields. An FC-72 solution of the dimeric flouroalkyldistannoxane 1 can be recycled repeatedly without having to recover the neat catalyst.
- Xiang, Jiannan,Toyoshima, Shinji,Orita, Akihiro,Otera, Junzo
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p. 3670 - 3672
(2007/10/03)
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- Me2NSO2Cl and N,N-dimethylamines; a novel and efficient agent for esterification, amidation between carboxylic acids, and equimolar amounts of alcohols and amines
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Various carboxylic esters or amides were prepared in good to excellent yields between carboxylic acids and equimolar amounts of alcohols or amines under very mild conditions using dimethylsulfamoyl chloride (Me2NSO2Cl) combined with N,N-dimethylamines. The choice of the sulfamoyl chloride and the amine is crucial for the reactions.
- Wakasugi, Kazunori,Nakamura, Atsushi,Tanabe, Yoo
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p. 7427 - 7430
(2007/10/03)
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- Diphenylammonium triflate (DPAT): Efficient catalyst for esterification of carboxylic acids and for transesterification of carboxylic esters with nearly equimolar amounts of alcohols
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Diphenylammonium triflate (DPAT) efficiently catalyzed esterification between equimolar amounts of carboxylic acids and alcohols in good to excellent yields under mild reaction conditions. Transesterification of carboxylic esters with a slight excess of alcohols also proceeded using DPAT as catalyst with TMSCl as a co-catalyst. (C) 2000 Elsevier Science Ltd.
- Wakasugi, Kazunori,Misaki, Tomonori,Yamada, Kayo,Tanabe, Yoo
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p. 5249 - 5252
(2007/10/03)
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- Efficient acylation of alcohols with acylthiazolidine-2-thiones and cesium fluoride
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Primary alcohols are acylated in good yield under almost neutral conditions with 3-acylthiazolidine-2-thiones and cesium fluoride.For secondary alcohols, the yield is improved by the addition of zinc bromide. t-Butanol is not acylated.
- Yamada, M.,Yahiro, S.,Yamano, T.,Nakatani, Y.,Ourisson, G.
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p. 824 - 829
(2007/10/02)
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