Anomeric hydroperoxides derived from 3,4,6-tri-O-benzyl-galactose and glucose were used for enantioselective epoxidation of naphthoquinone (12), chalcone (13), (E)-1,2-dibenzoyl ethylene (14) and (E)-iso-butyryl-phenyl ethylene (15). In the presence of sodium hydroxide, the epoxidations showed exceptional high asymmetric induction. The exchange of sodium by a potassium ion resulted in a low asymmetric
Remarkable effect of tris(4-fluorophenyl)phosphine oxide on the stabilization of chiral lanthanum complex catalysts. A new and practical protocol for the highly enantioselective epoxidation of conjugated enonesElectronic supplementary information (ESI) available: HPLC analysis of 2, 1H NMR data for 3 and 4, and crystal data for 5. See http://www.rsc.org/suppdata/ob/b4/b405882h/
A new and efficient chiral catalyst system, lanthanum–chiral BINOL–tris(4-fluorophenyl)phosphine oxide–cumene hydroperoxide, was developed for the epoxidation of α,β-unsaturated ketones thus providing the corresponding epoxy ketones with excellent enantioselectivities (up to >99% ee) in good to excellent yields at room temperature.
Diastereo- and enantioselective synthesis of α,β-epoxyketones using aqueous NaOCl in conjunction with dihydrocinchonidine derived phase-transfer catalysis at room temperature. Scope and limitations
作者:Barry Lygo、Stuart D. Gardiner、Michael C. McLeod、Daniel C. M. To
DOI:10.1039/b706546a
日期:——
In this paper we present studies into the scope and limitations of asymmetric PTC epoxidation of enones and the oxidationâepoxidation of allylic alcohols using aqueous NaOCl in conjunction with a dihydrocinchonidine derived quaternary ammoniumsaltcatalyst.
Scoping the triphasic/PTC conditions for the Juliá–Colonna epoxidation reaction
作者:Thomas Geller、Christa M. Krüger、H.-Christian Militzer
DOI:10.1016/j.tetlet.2004.04.189
日期:2004.6
A new, highly efficient procedure for the Juliá–Colonnaepoxidation is reported. Based on the original triphasic protocol it is shown that the co-catalysis of the reaction with phase transfer catalysts results in a dramatic increase of reactivity and sometimes also in a higher enantiomeric excess of product. The required amount of polyamino acid can be significantly reduced under the new conditions
Development of the Juliá asymmetric epoxidation reaction. Part 2. Application of the oxidation to alkyl enones, enediones and unsaturated keto esters
作者:Wolfgang Kroutil、M. Elena Lasterra-Sánchez、Samuel J. Maddrell、Patrick Mayon、Phillip Morgan、Stanley M. Roberts、Steven R. Thornton、Christine J. Todd、Melek Tüter
DOI:10.1039/p19960002837
日期:——
Polyleucine-based systems have been used to catalyse the asymmetric oxidation of a variety of alkyl enones 1-4,9-14, an enynone 16 and a dienone 17 to afford the corresponding epoxides 5-8, 18-26 in good to excellent yield and optical purity. A range of enediones 30-32, 34 and one unsaturated keto ester 33 have also been epoxidised stereoselectively to afford optically active epoxides 35-39. The epoxidations were carried out with basic peroxide as the oxidant; the polyleucine catalyst was prepared from leucine N-carboxyanhydride using 1,3-diaminopropane, water (employing a humidity cabinet) or a polystyrene immobilised amine as the initiator. Preliminary mass spectral data on material derived from L-leucine and 1,3-diaminopropane (DAP-PLL) suggest that the catalyst consists of material that contains 22 +/- 10 leucine residues.