852913-25-8Relevant articles and documents
Organocatalytic Enantio- and Diastereoselective Construction of syn-1,3-Diol Motifs via Dynamic Kinetic Resolution of in Situ Generated Chiral Cyanohydrins
Matsumoto, Akira,Asano, Keisuke,Matsubara, Seijiro
, p. 2688 - 2692 (2019/04/30)
An organocatalytic method for the asymmetric synthesis of syn-1,3-dioxanes as protected 1,3-diols via dynamic kinetic resolution of in situ generated chiral cyanohydrins has been developed. This method involves a reversible cyanohydrin formation/hemiaceta
TRANSFORMATIONS OF MESO-LACTIDE
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Paragraph 0074; 0075, (2018/09/18)
B/N Lewis pairs have been discovered to catalyze rapid epimerization of meso-lactide (LA) or LA diastereomers quantitatively into rac-LA. The obtained rac-LA can be kinetically polymerized into poly(L-lactide) and optically resolved D-LA, with a high stereoselectivity factor kL/kD of 53 and an ee value of 91% at 50.6% monomer conversion, by a bifunctional chiral catalyst. The epimerization and enantioselective polymerization can be coupled into a one-pot process for transforming meso-LA directly into poly(L-lactide) and D-LA.
Asymmetric Cycloetherification by Bifunctional Organocatalyst
Asano, Keisuke,Matsubara, Seijiro
, p. 4243 - 4253 (2018/07/03)
Attempts to obtain enantiomerically enriched tetrahydrofuran derivatives via an intramolecular oxy -Michael addition reaction of ?-hydroxyenone is discussed. Despite previous difficulties associated with the asymmetric induction of this reaction, which can proceed even without a catalyst, a highly efficient asymmetric induction was realized using a bifunctional organocatalyst derived from a cinchona alkaloid. The reaction could be extended to ζ-hydroxyenone to yield an optically active tetrahydropyran derivative with a high ee. In these reactions, it is important for the gentle acidic and basic sites in the bifunctional organocatalyst to be arranged properly within the molecular skeleton of the catalyst. The high performance asymmetric induction relied on the affinity of the catalyst for the substrate, which played an important role. A disubstituted tetrahydropyran synthesis could be effectively performed via kinetic resolution using ζ-hydroxyenone containing a secondary alcohol moiety using a chiral phosphoric acid catalyst.
Intramolecular Chirality Transfer [2 + 2] Cycloadditions of Allenoates and Alkenes
Xu, Yao,Hong, Young J.,Tantillo, Dean J.,Brown, M. Kevin
, p. 3703 - 3706 (2017/07/26)
Intramolecular chirality transfer [2 + 2] cycloaddition of enantiomerically enriched allenoates and alkenes is presented. The use of a chiral catalyst was found to be critical to achieve high levels of diastereoselectivity compared to use of an achiral catalyst. The method developed leads to highly substituted cyclobutanes that would be difficult to prepare by alternative methods.
Procedure-controlled enantioselectivity switch in organocatalytic 2-oxazolidinone synthesis
Fukata, Yukihiro,Asano, Keisuke,Matsubara, Seijiro
, p. 12160 - 12163 (2013/09/23)
In a novel organocatalytic formal [3 + 2] cycloaddition to afford chiral 2-oxazolidinones, an enantioselectivity switch could be induced by changing the manner of addition of the reactants, even when the reaction components (cinchona-alkaloid-derived aminothiourea catalyst, substrates, and solvent) were the same.
Asymmetric catalytic cycloetherification mediated by bifunctional organocatalysts
Asano, Keisuke,Matsubara, Seijiro
, p. 16711 - 16713 (2011/12/03)
Oxacyclic structures such as tetrahydrofuran (THF) rings are commonly found in many bioactive compounds, and this has led to several efforts toward their stereoselective syntheses. However, the process of catalytic asymmetric cycloetherification for their straightforward synthesis has remained a challenge. In this study, we demonstrate a novel asymmetric synthesis method for THF via the catalytic cycloetherification of ε-hydroxy-α,β- unsaturated ketones mediated by cinchona-alkaloid-thiourea-based bifunctional organocatalysts. This catalytic process represents a highly practical cycloetherification method that provides excellent enantioselectivities, even with low catalyst loadings at ambient temperature.