On the use of C2-symmetric aziridines as chiral auxiliaries
摘要:
A systematic study has been made of the utility of readily available C-2-symmetric aziridines as auxiliaries for asymmetric alkylation and aldol reactions of amide enolates. Aziridines with suitably placed oxygen atoms in the side chains proved to be useful for alkylation reactions (d.e. values up to >98%) and the results are explained in terms of an intramolecularly chelated Z-enolate species, which could be observed directly by means of NMR spectroscopy. In contrast, aziridine auxiliaries lacking side-chain oxygens performed better in aldol reactions (syn selectivity up to 98% d.e.) for which a Zimmerman-Traxler transition state is proposed. After reaction, the auxiliaries can be cleaved off nondestructively under mild conditions to afford either optically pure aldehydes or carboxylic acids.
A compound and method for producing an enantiomerically enriched epoxide from an olefin using a chiral ketone and an oxidizing agent is disclosed.
一种化合物及其生产方法被披露,该方法使用手性酮和氧化剂从烯烃生产具有对映体富集的环氧乙烷。
An Efficient Catalytic Asymmetric Epoxidation Method
作者:Zhi-Xian Wang、Yong Tu、Michael Frohn、Jian-Rong Zhang、Yian Shi
DOI:10.1021/ja972272g
日期:1997.11.1
This article describes a highly effective catalyticasymmetricepoxidation method for olefins using potassium peroxomonosulfate (Oxone, Dupont) as oxidant and a fructose-derived ketone (1) as catalyst. High enantioselectivies have been obtained for trans-disubstituted and trisubstituted olefins which can bear functional groups such as tributylsilyl ether, acetal, chloride, and ester. The enantiomeric
Asymmetric Epoxidation of Fluoroolefins by Chiral Dioxirane. Fluorine Effect on Enantioselectivity
作者:O. Andrea Wong、Yian Shi
DOI:10.1021/jo901553t
日期:2009.11.6
The asymmetricepoxidation of various fluoroolefins has been studied using chiral ketone catalyst, and up to 93% ee was achieved with fructose-derivedketone 1.
已经使用手性酮催化剂研究了各种氟代烯烃的不对称环氧化,果糖衍生的酮1实现了高达 93% 的 ee 。
Selective manganese-mediated transformations using the combination:
作者:István E Markó、Paul R. Richardson、Mark Bailey、Anita R. Maguire、Niall Coughlan
DOI:10.1016/s0040-4039(97)00309-2
日期:1997.3
A novel manganese reagent, generated from KMnO4 and Me3SiCl, in the presence of a quaternaryammonium salt, is shown to smoothly dichlorinate alkenes, open epoxides and chemoselectively oxidise sulfides to sulfoxides.
Chiroptical Protocol for the Absolute Configurational Assignment of Alkyl-Substituted Epoxides Using Bis(zinc porphyrin) as a CD-Sensitive Bidentate Host
The absoluteconfigurations of simple alkyl-substituted chiral epoxides not bearing other ligating groups are readily determined via the exciton-coupled circular dichroism (ECCD) protocol using bidentate bis(zinc porphyrin) host system BP1 as a CD-sensitive chirality probe. In this situation, chiral epoxides can successfully be incorporated into the cleft of V-shaped host BP1 by double coordination