- Enantioselective acyl-transfer catalysis by fluoride ions
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The asymmetric nucleophilic catalysis by fluoride ions at a carbon-based electrophile has been demonstrated for the first time. Using a library of ad hoc designed bifunctional phase-transfer catalysts in which both the anion and the cation are directly involved in the reaction, the desymmetrisation of meso-succinic and -glutaric anhydrides is possible.19F NMR spectroscopic studies support the intermediacy of an acyl fluoride intermediate.
- Craig, Ryan,Litvajova, Mili,Cronin, Sarah A.,Connon, Stephen J.
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supporting information
p. 10108 - 10111
(2018/09/18)
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- A simple method for resolution of endo-/exo-monoesters of trans-norborn-5-ene-2,3-dicarboxylic acids into their enantiomers
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Separation of optical isomers obtainable from trans-norborn-5-ene-2,3-dicarboxylic acid methyl and tert-butyl monoesters was performed by crystallization of the respective salts prepared with (R)- and (S)-1-phenylethylamine. Starting from racemic endo-monomethyl ester of trans-norborn-5-ene-2,3-dicarboxylic acid, prepared by partial hydrolysis of the cyclopentadiene-dimethyl fumarate adduct, the corresponding (2R, 3R)-endo-monoester was isolated in 97% enantiomeric excess (ee) yield after seven repeated crystallizations from tetrachloromethane. Starting from exo-mono-tert-butyl ester of the same acid, prepared by alcoholysis of the cyclopentadiene-maleic anhydride adduct followed by isomerization, (2R, 3R)-exo-monoester was isolated in >98% ee yield after four repeated crystallizations from ethanol. Crystallization of the acids from the mother liquor yielded products with inverse stereochemical configuration.
- Kovalenko, Vitaly N.,Kozyrkov, Yurii Yu.
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p. 151 - 155
(2015/03/04)
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- New exo/endo selectivity observed in monohydrolysis of dialkyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates
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New monohydrolysis reactions of several exo or endo dimethyl or diethyl bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylates showed higher selectivity toward monohydrolyses of exo-carboalkoxy groups, although the reaction centers are located away from the norborne
- Niwayama, Satomi,Hiraga, Yoshikazu
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p. 8567 - 8570
(2007/10/03)
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- 1H NMR study of esterification of norbornenedicarboxylic acid anhydride by lower aliphatic alcohols
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Kinetics of esterification of norbornenedicarboxylic acid anhydride by methanol, ethanol, and isopropyl alcohol (both absolute and moist) were studied by 1H NMR spectroscopy. Dependence of the reaction rate on the nature of alcohol was determined. Copyright
- Artem'eva,Kudryavtsev,Chupans,Denisov
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p. 440 - 442
(2007/10/03)
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- Enzymatic optical resolution of norbornanecarboxylic esters using Pig Liver Esterase
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The hydrolysis of a series of norbornane-type carboxylic esters catalyzed by pig liver esterase (PLE) has been investigated.It was found that an exo-ester function (syn to the C7 methylene group) is hydrolyzed with high preference.Enantioselective hydrolysis can be accomplished when a vicinal carbonyl-containing function (ester, formyl, acetyl) is present in a trans position with respect to the exo ester.The regiospecifity of the enzymatic hydrolysis has been used for the separation of exo/endo mixtures of the cycloadducts derived from cyclopentadiene and alkene esters.The regiospecifity and enantioselectivity of the enzymatic hydrolysis of norbornane-type esters were analyzed in terms of Tamm's substrate model and also by Griengl's method.
- Gastel, F. J. C. van,Klunder, A. J. H.,Zwanenburg, B.
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p. 175 - 184
(2007/10/02)
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