An Organocatalytic Approach to 2-Hydroxyalkyl- and 2-Aminoalkyl Furanes
摘要:
The first enantioselective methodology for the synthesis of electron-poor 2-hydroxyalkyl- and 2-aminoalkyl furanes is demonstrated in this study. It utilizes a highly stereoselective organocatalytic one-pot reaction cascade: epoxidation or aziridination of alpha,beta-unsaturated aldehydes followed by Feist-Benary reaction of various 1,3-dicarbonyl compounds to give the target furanes. This efficient multibond forming reaction cascade benefits from low catalyst loadings and readily available starting materials. Furthermore, the possibility to interrupt the reaction sequence at the stage of the corresponding optically active 2-hydroxyalkyl- and 2-aminoalkyl 2,3-dihydrofuranes with three stereogenic centers is also presented. Finally, models which account for the formation of the optically active 2,3-dihydrofuranes are proposed.
Asymmetric Organocatalytic Epoxidation of α,β-Unsaturated Aldehydes with Hydrogen Peroxide
作者:Mauro Marigo、Johan Franzén、Thomas B. Poulsen、Wei Zhuang、Karl Anker Jørgensen
DOI:10.1021/ja051808s
日期:2005.5.1
The first asymmetricorganocatalytic epoxidation of α,β-unsaturatedaldehydes is presented. A chiral bisaryl−silyl-protected pyrrolidine acts as a very selective epoxidation organocatalyst using simple oxidation agents, such as hydrogen peroxide and tert-butyl hydroperoxide. The asymmetric epoxidation reactions proceed under environmental friendly reaction condition in, for example, water mixtures
介绍了 α,β-不饱和醛的第一个不对称有机催化环氧化反应。手性双芳基-甲硅烷基保护的吡咯烷使用简单的氧化剂(如过氧化氢和叔丁基过氧化氢)作为一种非常有选择性的环氧化有机催化剂。不对称环氧化反应在环境友好的反应条件下进行,例如,在醇的水混合物中,反应的范围通过以高产率和对映选择性 > 94% ee 形成光学活性的 α,β-环氧醛来证明。此外,还介绍了通过柠檬醛的不对称环氧化从螨虫直接合成性信息素。
Amine-Catalyzed Asymmetric Epoxidation of α,β-Unsaturated Aldehydes
The direct organocatalytic enantioselective epoxidation of α,β-unsaturated aldehydes with different peroxides is presented. Proline, chiral pyrrolidine derivatives, and amino acid-derived imidazolidinones catalyze the asymmetric epoxidation of α,β-unsaturated aldehydes. In particular, protected commercially available α,α-diphenyl- and α,α-di(β-naphthyl)-2-prolinols catalyze the asymmetric epoxidation
Direct organocatalytic asymmetric epoxidation of α,β-unsaturated aldehydes
作者:Henrik Sundén、Ismail Ibrahem、Armando Córdova
DOI:10.1016/j.tetlet.2005.10.128
日期:2006.1
The organocatalyticasymmetric epoxidation of α,β-unsaturatedaldehydes with peroxides or sodium percarbonate is presented. Chiral pyrrolidine derivatives, proline and amino acid derived imidazolidinones mediate the asymmetric epoxidation of α,β-unsaturatedaldehydes. For example, commercially available protected α,α-diphenyl-2-prolinol catalyzes the asymmetric formation of 2-epoxy-aldehydes in 81–95%
On the Mechanism of the Organocatalytic Asymmetric Epoxidation of α,β-Unsaturated Aldehydes
作者:Rebecca L. Davis、Kim L. Jensen、Björn Gschwend、Karl Anker Jørgensen
DOI:10.1002/chem.201303942
日期:2014.1.3
Mechanistic studies on the organocatalytic epoxidation of α,β‐unsaturated aldehydes explore the autoinductive behavior of the reaction and establish that the hydrate/peroxyhydrate of the product is acting as a phase‐transfer catalyst. Based on these studies, an improved methodology that provides high selectivities and decreased catalyst loading, through the addition of chloral hydrate, is developed