42726-73-8Relevant articles and documents
Studies of the Electronic Effects of Zinc Cluster Catalysts and Their Application to the Transesterification of β-Keto Esters
Agura, Kazushi,Hayashi, Yukiko,Wada, Mari,Nakatake, Daiki,Mashima, Kazushi,Ohshima, Takashi
supporting information, p. 1548 - 1554 (2016/06/01)
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).
Application of asymmetric alkylation of malonic diester with phase-transfer catalysis: Synthesis of LFA-1 antagonist BIRT-377
Kanemitsu, Takuya,Furukoshi, Saeka,Miyazaki, Michiko,Nagata, Kazuhiro,Itoh, Takashi
, p. 214 - 218 (2015/03/04)
An efficient asymmetric synthesis of LFA-1 antagonist BIRT-377 using enantioselective phase-transfer catalytic alkylation has been developed. The alkylation of α-monosubstituted tert-butyl methyl malonate was catalyzed by a quaternary ammonium salt derived from a cinchona alkaloid to obtain the product with a quaternary stereogenic carbon in high yield and with high enantioselectivity. The chiral α,α-disubstituted product thus obtained was transformed into BIRT-377 through alternating chemoselective deprotection of the two ester groups followed by Curtius rearrangement.
Iron(iii)-salan complexes catalysed highly enantioselective fluorination and hydroxylation of β-keto esters and N-Boc oxindoles
Gu, Xin,Zhang, Yan,Xu, Zhen-Jiang,Che, Chi-Ming
supporting information, p. 7870 - 7873 (2014/07/08)
Chiral iron(iii)-salan complexes catalysed highly enantioselective α-fluorination and α-hydroxylation of β-keto esters and N-Boc oxindoles to give the corresponding products in high yields and good-to-excellent ee values under mild reaction conditions. This journal is the Partner Organisations 2014.
Delineating origins of stereocontrol in asymmetric Pd-catalyzed α-hydroxylation of 1,3-ketoesters
Smith, Alexander M. R.,Rzepa, Henry S.,White, Andrew J. P.,Billen, Denis,Hii, King Kuok
supporting information; experimental part, p. 3085 - 3096 (2010/07/17)
Systematic studies of reaction conditions and subsequent optimization led to the identification of important parameters for stereoselectivity in the asymmetric α-hydroxylation reaction of 1,3-ketoesters. Enantioselectivities of up to 98% can be achieved for cyclic substrates and 88% for acyclic ketoesters. Subsequently, the combination of cyclic/acyclic ketoester, catalyst, and oxidant was found to have a profound effect on reaction rates and turnover-limiting steps. The stereochemistry of the reaction contradicts that observed for other similar electrophilic substitution reactions. This was rationalized by transition-state modeling, which revealed a number of cooperative weak interactions between oxidant, ligand, and counterion, together with C-H/π interactions that cumulatively account for the unusual stereoselectivity.
An efficient method for generation of α-oxoketenes: Cycloreversion of enolized Meldrum's acid derivatives
Sato, Masayuki,Ban, Hitoshi,Kaneko, Chikara
, p. 6689 - 6692 (2007/10/03)
A series of 6-methoxy- or siloxy-4H-1,3-dioxin-4-ones was synthesized from Meldrum's acids. These dioxinones underwent 4+2 cycloreversion to methoxy- or siloxycartbonylketenes and ketones quantitatively at 20-50°C. The ketenes were characterized by IR spectroscopy as well as by trapping with t-butanol. The ready cycloreversion of these enolized Meldrum's acid derivatives strongly indicates that the anomalously high susceptibility of Meldrum's acids to nucleophilic reagents is due to the participation of carboxyketenes generated through the cycloreversion of tautomeric 6-hydroxydioxinones.
Intramolecular Cyclopropanation: Stereospecific Synthesis of (E)- and (Z)-1-Aminocyclopropane-1-carboxylic Acids
Koskinen, Ari M. P.,Munoz, Luis
, p. 879 - 886 (2007/10/02)
tert-Butyl-substituted allyl malonates, prepared in two steps from malonic acid, are diazotized in high yields.The diazomalonates 7 undergo a stereospecific copper(I)-catalyzed cyclopropanation to give 1-(tert-butoxycarbonyl)-3-oxa-2-oxobicyclohexanes 8 which can be converted to the protected (E)- or (Z)-1-aminocyclopropane-1-carboxylic acids 10 or 15 via Curtius- or Hoffmann-type rearrangements, respectively.The sequences are short (six steps from malonic acid) and proceed with good overall yields (20-40percent overall from malonic acid).The free amino acids 12 and 13 can be liberated in two steps.
AN EASY SYNTHESIS OF MONOMETHYL MALONATE DERIVATIVES
Matoba, Katsuhide,Yamazaki, Takao
, p. 2955 - 2956 (2007/10/02)
Monomethyl malonates (IIIa-c and Va) were synthesized from Meldrum's acid (Ia) by treating with an excess of diazomethane in the corresponding alcohols and piperidine, respectively, in quantitative yields.In a similar manner, 5-p-chlorobenzyl Meldrum's acid (Ib) afforded the corresponding monomethyl malonate derivatives (IIIe, f, and Vb).The mechanism proposed for this reaction is described.KEYWORDS - Meldrum's acid; monomethyl malonate; half ester; ketene ester; 4,6-dioxo-1,3-dioxane
