Titanium catalysed enantioselective addition of allyltributyltin to aldehydes: a simple and easily reproducible procedure
作者:Henri Doucet、Maurice Santelli
DOI:10.1016/s0957-4166(00)00374-8
日期:2000.10
We describe here an extremely simple procedure for the enantioselective addition of allyltributyltin to aldehydes in the presence of a binaphthol-titanium complex. In toluene or pentane, the reaction can be performed at room temperature in the absence of molecular sieves without a decrease in the enantioselectivity. Enantiomeric excesses of up to 99% can be obtained in the most favourable cases. (C) 2000 Elsevier Science Ltd. All rights reserved.
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