- Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β-Keto Esters
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The electronic effects of tetranuclear zinc cluster catalysts on transesterification were investigated by changing the carboxylate ligands in the clusters. High catalyst activity crucially depended on the balance between Lewis acidity and Br?nsted basicity of the catalyst; this was consistent with the dual activation of both the electrophile and nucleophile by the cooperative zinc centers. In addition, tetranuclear zinc cluster catalysts achieved the transesterification of β-keto esters with unprecedented levels of broad substrate generality, in which a newly developed pentafluoropropionate-bridged zinc cluster and 4-dimethylaminopyridine additive greatly improved the reactivity of sterically congested α- and α,α-disubstituted β-keto esters. Lewis versus Br?nsted: High catalyst activity of zinc clusters on transesterification crucially depend on a balance between Lewis acidity and Br?nsted basicity of the catalyst. Zinc clusters, including a newly developed pentafluoropropionate-bridged zinc cluster, achieved the transesterification of β-keto esters with unprecedented levels of broad substrate generality (see figure).
- Agura, Kazushi,Hayashi, Yukiko,Wada, Mari,Nakatake, Daiki,Mashima, Kazushi,Ohshima, Takashi
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supporting information
p. 1548 - 1554
(2016/06/01)
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- Liquid crystalline cyclic tetramethyltetrasiloxanes containing coumarin moieties
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A series of new cyclic tetramethyltetrasiloxanes with coumarin units were synthesized. By a comparative study with their related vinyl terminated precursors, the liquid crystalline properties of the cyclic tetramethyltetrasiloxanes were investigated. The
- Tian, Yanqing,Akiyama, Eiichi,Nagase, Yu
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p. 1253 - 1258
(2007/10/03)
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- One-Pot synthesis of 5-Alkylthio-3H-1,2-dithiole-3-thiones: Advantages and scopes
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The reaction of dialkyl malonate esters with P2S5/S8 in boiling xylene in the presence of 2-mercaptobenzothiazole/ZnO as catalyst produces 5-alkylthio-3H-1,2-dithiole-3-thiones as major identifiable product. Moderate yields were obtained with malonate esters of primary alcohols. The reaction fails with malonate esters of secondary alcohols. Regarding the substituent in position two, dialkyl malonates with groups such as CH3, Ph, CH2Ph, OCH3 and Cl afford the corresponding 4-substituted derivatives whereas with Br and NO2 do not give the expected products. Some mechanistic evidences are described.
- Aimar,De Rossi
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p. 1749 - 1755
(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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- Process for the preparation of 3,5-dihydrocarbyl-4-hydroxybenzylmalonic acid esters
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Esters of 3,5-dihydrocarbyl-4-hydroxybenzylmalonic acid are prepared by reacting a 2,6-dihydrocarbyl-4-halomethylphenol with an ester of a 1,3-dicarboxylic acid in the presence of an alkali or an alkaline earth metal hydride. The products are useful as antioxidants.
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