Lewis Base Activation of Lewis Acids: Catalytic, Enantioselective Addition of Silyl Ketene Acetals to Aldehydes
作者:Scott E. Denmark、Gregory L. Beutner、Thomas Wynn、Martin D. Eastgate
DOI:10.1021/ja047339w
日期:2005.3.1
The concept of Lewisbase activation of Lewisacids has been reduced to practice for catalysis of the aldolreaction of silyl ketene acetals and silyl dienol ethers with aldehydes. The weakly acidic species, silicon tetrachloride (SiCl4), can be activated by binding of a strongly Lewis basic chiral phosphoramide, leading to in situ formation of a chiral Lewisacid. This species has proven to be a competent
Enantioselective Lewis Acid Catalyzed Michael Reactions of Alkylidene Malonates. Catalysis by <i>C</i><sub>2</sub>-Symmetric Bis(oxazoline) Copper(II) Complexes in the Synthesis of Chiral, Differentiated Glutarate Esters
作者:David A. Evans、Tomislav Rovis、Marisa C. Kozlowski、C. Wade Downey、Jason S. Tedrow
DOI:10.1021/ja002246+
日期:2000.9.1
C2-symmetricbis(oxazoline)−Cu(II) complexes 1 catalyze the Mukaiyama Michael reaction of alkylidene malonates and enolsilanes. The use of hexafluoro-2-propanol is essential to induce catalyst turnover. High enantioselectivities are exhibited by bulky alkylidene malonate β-substituents using catalyst 1a. The glutarate ester products are readily decarboxylated to provide chiral 1,5-dicarbonyl synthons
Lewis Base Activation of Lewis Acids. Addition of Silyl Ketene Acetals to Aldehydes
作者:Scott E. Denmark、Thomas Wynn、Gregory L. Beutner
DOI:10.1021/ja0282947
日期:2002.11.1
olefinic aldehydes as well as aliphatic aldehydes (albeit more slowly) with excellent enantioselectivity. The homologous tert-butyldimethylsilyl ketene acetal of tert-butyl propanoate adds with nearly exclusive anti diastereoselectivity to a similar range of aldehydes also with excellent enantioselectivity. The origin of the slower reaction rate with aliphatic aldehydes is revealed to be the formation of chlorosilyl
An Enantioselective, Intermolecular α-Arylation of Ester Enolates To Form Tertiary Stereocenters
作者:Zhiyan Huang、Zheng Liu、Jianrong (Steve) Zhou
DOI:10.1021/ja2066829
日期:2011.10.12
asymmetric α-arylation of carbonylcompounds, formation of tertiary centers with high enantioselectivity is a longstanding problem, due to easy enolization of the monoarylation products. Herein, we report such examples using a palladium catalyst supported by a new, (R)-H(8)-BINOL-derived monophosphine. Silyl ketene acetals, together with a weakly basic activator, were used as equivalents of ester anions
在过渡金属催化的羰基化合物的不对称α-芳基化中,由于单芳基化产物容易烯醇化,形成具有高对映选择性的三级中心是一个长期存在的问题。在此,我们报告了使用由新的 (R)-H(8)-BINOL 衍生的单膦支持的钯催化剂的示例。甲硅烷基乙烯酮缩醛与弱碱性活化剂一起用作酯阴离子的等价物,它们与芳基三氟甲磺酸酯以优异的对映体过量 (ee) 顺利反应。该反应的有效性在 92% ee 的 (S)-萘普生的克级合成中得到证明。
Acyclic stereoselection. Part 34. Stereoselection in the Michael addition reaction. 4. Diastereofacial preferences in Lewis acid-mediated additions of enolsilanes to chiral enones