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
An in situ procedure for catalytic, enantioselective acetate aldol addition. Application to the synthesis of (R)-(−)-epinephrine
作者:Robert A. Singer、Erick M. Carreira
DOI:10.1016/s0040-4039(96)02515-4
日期:1997.2
experimental procedure for the enantioselective, catalyticacetate aldol addition reaction. The addition of Me3SiCl and Et3N circumvents the azeotropic removal of the released isopropanol upon treating ligands 1 and 2 with Ti(OiPr)4. Importantly, this new procedure maintains the salient features of the catalytic process we originally described: high yields and enantioselectivities, low catalyst loads, and
我们报道了催化剂3的原位制备,其实质上简化了对映选择性的,催化的乙酸酯羟醛加成反应的实验程序。Me 3 SiCl和Et 3 N的添加避免了用Ti(O i Pr)4处理配体1和2时共沸除去释放的异丙醇。重要的是,这种新方法保持了我们最初描述的催化过程的显着特征:高收率和对映选择性,低催化剂负载以及便捷的反应时间和温度。我们已将新程序应用于(R来自商业试剂的)-(-)-肾上腺素,总产率为45%。
Catalytic, Enantioselective Aldol Additions with Methyl and Ethyl Acetate O-Silyl Enolates: A Chiral Tridentate Chelate as a Ligand for Titanium(IV)
作者:Erick M. Carreira、Robert A. Singer、Wheeseong Lee
DOI:10.1021/ja00098a065
日期:1994.9
Asymmetric catalysis of the Mukaiyama aldol reaction has been reported with complexes derivedfrom Al, B, Sn(II), and Ti(IV). The levels of asymmetric induction for the addition of propionate-, isobutyrate-, and acetate-derived silyl thioketene acetals to aldehydes parallel those obtained with chiral-auxiliary-based methodologies. However, silylketeneacetalsderivedfrom O-alkyl acetates uniformly
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
Configuration Sampling With Five‐Membered Atropisomeric
<i>P</i>
,
<i>N</i>
‐Ligands
作者:Gaurav Dahiya、Mukesh Pappoppula、Aaron Aponick
DOI:10.1002/anie.202102642
日期:2021.9
systematic variation of atropisomeric C1-symmetric P,Nligands to incrementally change the position of the groups within the chiral pocket without modifying their steric parameters. More specifically, the effects of systematic modification of the nitrogen heterocycle in atropisomeric C1-symmetric stack ligands have been investigated in this study. The versatility and applicability of this approach
在这里,我们报告了一种对阻转异构体 C 1对称 P,N 配体进行系统变异的策略,以逐步改变手性袋中基团的位置,而不修改它们的空间参数。更具体地,本研究已经研究了阻转异构C 1对称堆叠配体中氮杂环的系统修饰的影响。这种方法的多功能性和适用性已在机械上不同的催化对映选择性转化中得到证明,从而鉴定了用于高度对映选择性合成有机硼烷的 P,N-配体。