Asymmetric epoxidation of α,β-unsaturated aldehydes catalyzed by a spiro-pyrrolidine-derived organocatalyst
摘要:
The asymmetric epoxidation of alpha,beta-unsaturated aldehydes, catalyzed by a spiro-pyrrolidine (SPD)-derived organocatalyst, has been accomplished with good diastereoselectivities (up to dr >20:1) and with high to excellent enantioselectivities (up to 99% ee). (C) 2016 Elsevier Ltd. All rights reserved.
Fluorinated Organocatalysts for the Enantioselective Epoxidation of Enals: Molecular Preorganisation by the Fluorine-Iminium Ion Gauche Effect
作者:Eva-Maria Tanzer、Lucie E. Zimmer、W. Bernd Schweizer、Ryan Gilmour
DOI:10.1002/chem.201201316
日期:2012.9.3
The fluorine‐iminium ion gauche effect is triggered upon union of a secondary β‐fluoroamine and an α,β‐unsaturated aldehyde, providing a useful strategy for controlling the molecular topology of intermediates that are central to organocatalytic processes. The β‐fluoroamine (S)‐2‐(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselectiveepoxidation of α,β‐unsaturated aldehydes
A Comparison of Intrazeolite and Solution Singlet Oxygen Ene Reactions of Allylic Alcohols
作者:Edward L. Clennan、Dong Zhang、Jamie Singleton
DOI:10.1562/2006-01-09-ra-768
日期:2006.9
of four allylic alcohols and for comparison an allylic ether have been examined both in solution and in zeolite Y. Brønsted acid sites in the zeolite were shown to inducedecomposition of several of the allylic alcohols. Treatment of the zeolites with pyridine removed these acid sites and allowed intrazeolite reactions of the allylic alcohols without interference from decomposition. Control reactions
摘要 四种烯丙醇和烯丙醚的单线态氧烯反应已在溶液和 Y 沸石中进行了检测。沸石中的布朗斯台德酸位被证明会诱导几种烯丙醇的分解。用吡啶处理沸石去除了这些酸性位点并允许烯丙醇在沸石内反应而不受分解干扰。与对分解呈惰性的烯丙醇的控制反应提供证据,证明沸石迷宫中吡啶的存在不会影响产品组成。
An Expeditious Enantioselective
Synthesis of Methyl <i>trans</i>-Chrysanthemate
作者:Alain Krief、Willy Dumont、Diane Baillieul
DOI:10.1055/s-2002-34388
日期:——
Methyl trans-chrysanthemate has been prepared in few steps from isopropylidenediphenylsulfurane and methyl (E)-3-(3,3-dimethyloxiran-2-yl)prop-2-enoate. The latter was obtained from methyl 4-oxobutenoate or 3-methylbut-2-en-1-ol. The Sharpless catalytic epoxidation reaction allows an asymmetric version of this transformation.
Sespendole is an indole sesquiterpene alkaloid bearing two isoprenyl groups, one of which is highly oxidized. Herein, we disclose an eight-step synthesis of the aromatic fragment of sespendole in an optically pure form, starting from 4-bromo-2-fluoronitrobenzene. The key steps were a Claisen rearrangement at room temperature for introduction of the prenyl group and a coupling between the dianion generated