216099-51-3Relevant academic research and scientific papers
Chiral Lewis acid catalyzed resolution of racemic enol ester epoxides. Conversion of both enantiomers of an enol ester epoxide to the same enantiomer of acyloxy ketone
Feng, Xiaoming,Shu, Lianhe,Shi, Yian
, p. 2831 - 2836 (2007/10/03)
This paper describes an efficient kinetic resolution of racemic enol ester epoxides via a chiral Lewis acid catalyzed rearrangement. Both enantiomerically enriched enol ester epoxides and α-acyloxy ketones can be obtained through this resolution. A positive nonlinear effect is observed in this process. By taking advantage of the mechanistic duality in acid-catalyzed enol ester epoxide rearrangement, we can completely convert a racemic enol ester epoxide into an enantiomerically enriched α-acyloxy ketone by treatment with a catalytic amount of a chiral Lewis acid followed by a catalytic amount of an achiral protic acid.
Enantioselective epoxidation of alkenes catalyzed by 2-fluoro-N-carbethoxytropinone and related tropinone derivatives
Armstrong, Alan,Ahmed, Ghafoor,Dominguez-Fernandez, Belen,Hayter, Barry R.,Wailest, J. Steven
, p. 8610 - 8617 (2007/10/03)
Several α-substituted N-carbethoxytropinones have been evaluated as catalysts for asymmetric epoxidation of alkenes with Oxone, via a dioxirane intermediate. α-Fluoro-N-carbethoxytropinone (2) has been studied in detail and is an efficient catalyst which does not suffer from Baeyer-Villiger decomposition and can be used in relatively low loadings. This ketone was prepared in enantiomerically pure form using chiral base desymmetrization of N-carbethoxytropinone. Asymmetric epoxidation catalyzed by 2 affords epoxides with up to 83% ee. Among other derivatives tested, the α-acetoxy derivative 7 affords the highest enantioselectivities.
Enantioselective synthesis and stereoselective rearrangements of enol ester epoxides
Zhu,Shu,Tu,Shi
, p. 1818 - 1826 (2007/10/03)
Enol esters can be epoxidized with high enantioselectivities using the fructose-derived chiral ketone 1 as catalyst and Oxone as oxidant. A detailed study of enantiomerically enriched enol ester epoxides has revealed that the acid-catalyzed rearrangement can proceed through two distinct pathways, one with retention of configuration and the other with inversion. The competition between the two pathways is highly dependent upon the nature of the acid catalyst. A strong acid favors retention of configuration and a weak acid favors inversion of configuration. Under thermal conditions, these epoxides rearrange highly stereoselectively with inversion of configuration. Either enantiomer of an α-acyloxy ketone can be formed from one enantiomer of an enol ester epoxide by judicious choice of reaction conditions.
Highly enantioselective epoxidation of enol silyl ethers and esters
Zhu, Yuanming,Tu, Yong,Yu, Hongwu,Shi, Yian
, p. 7819 - 7822 (2007/10/03)
High enantioselectivities have been obtained for asymmetric epoxidation of enol silyl ethers and esters using a fructose-derived chiral ketone as catalyst and Oxone as oxidant.
