Asymmetric synthesis using diisopropyl tartrate modified (E)- and (Z)-crotylboronates: preparation of the chiral crotylboronates and reactions with achiral aldehydes
作者:William R. Roush、Kaori Ando、Daniel B. Powers、Alan D. Palkowitz、Ronald L. Halterman
DOI:10.1021/ja00173a023
日期:1990.8
Crotylboronates undergo highly diastereo- and enantioselective reactions with aliphatic (linear or α-monobranched; 72-91% ee), aromatic and α,β-unsaturated aldehydes (55-74% ee). The reaction diastereoselectivity closely parallels the reagent isomeric purity especially for reactions performed at −78 o C. The enantioselectivity is best in toluene for all substrates except benzaldehyde where best results
巴豆基硼酸酯与脂肪族(线性或 α-单支链;72-91% ee)、芳香族和 α,β-不饱和醛(55-74% ee)发生高度非对映选择性和对映选择性反应。反应的非对映选择性与试剂异构体纯度密切相关,特别是对于在 -78 o C 下进行的反应。对所有底物的对映选择性在甲苯中最佳,但苯甲醛除外,因为苯甲醛在 THF 中获得最佳结果。本研究中合成的 14 种高烯丙醇中有 9 种的相对和绝对立体化学是通过与 Sharpless 不对称环氧化制备的环氧醇的相关性来确定的
Enantioselective synthesis using diisopropyl tartrate modified (E)- and (Z)-crotylboronates: Reactions with achiral aldehydes
作者:William R. Roush、Kaori Ando、Daniel B. Powers、Ronald L. Halterman、Alan D. Palkowitz
DOI:10.1016/s0040-4039(00)80816-3
日期:1988.1
The reactions of diisopropyl tartrate modified( E)- and (Z)-crotylboronates with representative achiral aldehydes are described. Enantioselectivity ranges from 55–91% e.e. depending on the aldehyde employed.
syn-Selective crotylation of aldehydes using bismuth-crotyl bromide-(1-butyl-3-methylimidazolium bromide) combination: some synthetic applications
作者:Dibakar Goswami、Mrunesh R. Koli、Sucheta Chatterjee、Subrata Chattopadhyay、Anubha Sharma
DOI:10.1039/c7ob00626h
日期:——
The Bi-[bmim][Br] combination has been found to offer high syn-selectivity in the crotylation of aldehydes with crotylbromide using practically stoichiometric amounts of the reagents. The room temperature ionic liquid (RTIL), [bmim][Br], activated Bi metal in the presence of oxygen to produce crotylbismuthdibromide, which reacted with the aldehydes at room temperature. The major anti–syn diastereomeric
Nozaki−Hiyama−Kishi Reactions Catalytic in Chromium
作者:Alois Fürstner、Nongyuan Shi
DOI:10.1021/ja9625236
日期:1996.1.1
chromium-catalyzed additions of organic halides to aldehydes (“Nozaki−Hiyama−Kishi reactions”). The reactions are mediated by trimethylchlorosilane, and the active Cr2+ species is constantly recycled by means of nontoxic, commercial manganese powder as the stoichiometric reductant. This method nicely applies to different substituted aryl, heteroaryl, alkynyl, alkenyl, and allylhalides as well as to alkenyl triflates
to produce unisolable allylchromium species which add efficiently to aldehydes or ketones with high degree of stereo- and chemoselectivity. Particularly, high threo selectivity is observed in the reaction of aldehydes and 1-bromo-2-butene and is ascribed to a chair-like six-membered transition state. Simple reduction of allylic and benzylic halides produces biallyls and bibenzyls, while gem-dibromocyclopropanes