title: Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β-Keto Esters.
abstract: 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 Brønsted 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.
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, CREST, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Kazushi
authors.initials: K
authors.lastname: Agura
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, CREST, Toyonaka, Osaka, 560-8631, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Hayashi
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, CREST, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Mari
authors.initials: M
authors.lastname: Wada
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, CREST, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan.
authors.forename: Daiki
authors.initials: D
authors.lastname: Nakatake
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, CREST, Toyonaka, Osaka, 560-8631, Japan. mashima@chem.es.osaka-u.ac.jp.
authors.forename: Kazushi
authors.initials: K
authors.lastname: Mashima
authors.affiliation: Graduate School of Pharmaceutical Sciences, Kyushu University, CREST, Maidashi, Higashi-ku, Fukuoka, 812-8582, Japan. ohshima@phar.kyushu-u.ac.jp.
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohshima
keywords: beta-keto esters; electronic effects; synthesis design; transesterification; zinc