Proline-Based <i>N</i>-Oxides as Readily Available and Modular Chiral Catalysts. Enantioselective Reactions of Allyltrichlorosilane with Aldehydes
作者:John F. Traverse、Yu Zhao、Amir H. Hoveyda、Marc L. Snapper
DOI:10.1021/ol050814q
日期:2005.7.1
as an effective catalyst for the reaction of allyltrichlorosilane with aryl and alpha,beta-unsaturated aldehydes at room temperature to afford the desired homoallylic alcohols in up to 92% ee. The chiral catalyst can be easily prepared from optically pure proline in three simple steps and 60% overall yield.
A series of enantiomerically pure mono- and bis-aryl tert-butyl sulfoxides were synthesised to promote the enantioselective allylation of aldehydes with allyltrichlorosilane. Moderate to good yields and modest to high enantioselectivities were achieved. The absence of nonlinear effect, spacer effect, promoter loading and concentration effect indicate that only one molecule of aryl tert-butyl sulfoxide is involved in the stereodetermining step.
Catalytic Enantioselective Allyl- and Crotylboration of Aldehydes Using Chiral Diol•SnCl<sub>4</sub> Complexes. Optimization, Substrate Scope and Mechanistic Investigations
作者:Vivek Rauniyar、Huimin Zhai、Dennis G. Hall
DOI:10.1021/ja8016076
日期:2008.7.1
induction in the allylboration of aldehydes by commercially available allylboronic acid pinacol ester 1a. The corresponding homoallylic alcohol products of synthetically useful aliphatic aldehydes are obtained in excellent yields with up to 98:2 er. This combined acid manifold is also efficient in catalyzing the diastereo- and enantioselective crotylboration of aldehydes, thus providing the propionate
我们报告了一类新的 C2 对称手性二醇,其源自对苯二酚骨架。在 Yamamoto 的路易斯酸辅助布朗斯台德酸度(LBA 催化)概念下,这些二醇与 SnCl 4 的组合导致可商购的烯丙基硼酸频哪醇酯 1a 在醛的烯丙基硼化中产生高水平的不对称诱导。合成有用的脂肪醛的相应高烯丙醇产品以高达 98:2 的产率获得。这种组合的酸歧管还可有效催化醛的非对映选择性和对映选择性巴豆基硼化反应,从而提供 >95:5 dr 和高达 98:2 er 的丙酸酯单元。最佳二醇 x SnCl4 配合物 Vivol (4m) x SnCl4 的 X 射线晶体结构,明确显示了这种 LBA 催化剂的 Brønsted 酸性特征及其高度不对称的环境。进一步的控制排除了可能的硼与手性二醇的酯交换机制,并指出频哪醇烯丙基硼酸酯 1 的 LBA 催化剂衍生的活化。由于二醇 x SnCl4 复合物的缓慢解离,需要少量过量的二醇为了抑制由游离
Bispalladacycle Catalyzed Nucleophilic Enantioselective Allylation of Aldehydes by Allylstannanes
Bimetallic catalysis: The first palladium catalysts capable of controlling asymmetric nucleophilic allylations of aldehydes with allyltributyltin are reported. Unprecedented TONs for this reaction type were achieved (up to 620). The method is also tolerating electronically and sterically unfavorable substrates. A transmetallation occurs, favoring an η1-allyl coordination mode with the reported bispalladacycle
双金属催化:报道了第一个能够控制醛与烯丙基三丁基锡的不对称亲核烯丙基化的钯催化剂。这种反应类型的 TON 达到了前所未有的水平(高达 620)。该方法还可以容忍电子和空间上不利的底物。发生金属转移,有利于 η 1 -烯丙基配位模式与报道的双钯环催化剂,而对于相应的单钯环催化剂,非生产性的 η 3 -配位占主导地位。
Asymmetric Allylation of Aldehydes Catalyzed by Simple Dual Small Organic Molecules: L-Proline and L-Prolinol
作者:Guo-hong Chen、Ling-yan Liu、Xiao-ning Wei、Wei-xing Chang、Jing Li
DOI:10.1246/cl.2010.1013
日期:2010.9.5
A novel and simple methodology for the asymmetric allylation of aldehydes was reported. Double small organic molecules such as l-proline and l-prolinol were first employed for providing a chiral environment so as to afford chiral homoallylic alcohols in high yields and moderate enantioselectivities in our protocol.