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
Process for preparation of substituted olefins
申请人:Rikagaku Kenkyusho
公开号:US04263212A1
公开(公告)日:1981-04-21
The present invention relates to a process for the preparation of aromatic or furyl substituted olefins, which comprises reacting an olefinic compound with an aromatic compound or furan compound in the presence of carbon monoxide by using a rhodium carbonyl complex as a catalyst to form a corresponding aromatic or furyl substituted olefin.
TERT-Butylstyrene is prepared by a one-step reaction of tert-butylbenzene, ethylene and oxygen in the presence of a catalyst prepared by treating metallic palladium or fatty acid salts thereof with pyridine. The yield is increased by using together therewith a promoter prepared by treating one or more metals or oxides or fatty acid salts thereof, the metals being selected from the group consisting of copper, nickel, manganese, uranium and thallium. The reaction is carried out at a temperature between 50.degree. to 300.degree.C under a pressure of up to 100 kg/cm.sup.2.
The thermal formation of bialkyls from alkylmetals
作者:Björn Åkermark、Anders Ljungqvist
DOI:10.1016/s0022-328x(00)85875-1
日期:1979.11
The thermaldecomposition of neophyltransition metal complexes has been investigated, in particular, the products of reductive elimination and the symmetry aspects of this reaction. Bineophyl (1) was generally the major product from reproductive elimination. A number of other dimeric products were formed, via routes which must involve transmetallation, α-elimination and, in a few cases, radical formation