Cheap, readily available, air stable, nontoxic, and environmentally benign iron salts such as Fe(acac)3 are excellent precatalysts for the cross-coupling of Grignardreagents with alkenyl triflates and acid chlorides. Moreover, it is shown that dichloroarene and -heteroarene derivatives as the substrates can be selectively monoalkylated by this method. All cross-coupling reactions proceed very rapidly
廉价,容易获得,空气稳定,无毒且对环境无害的铁盐,例如Fe(acac)3是格氏试剂与链烯基三氟甲磺酸酯和酰氯交叉偶联的出色的预催化剂。此外,显示出通过该方法可以将作为底物的二氯亚芳基和-杂亚芳基衍生物选择性地单烷基化。所有交叉偶联反应在特别温和的条件下均能非常快速地进行,结果证明与两个反应伙伴中的各种官能团均相容。对制备结果的详细分析表明,铁催化的碳键形成可以通过不同的途径发生。因此,甲基卤化镁的反应可能包含铁酸盐配合物作为活性成分,而格氏试剂与两个或多个碳原子的反应则受到形式组成[Fe(MgX)2 ]的高度还原的铁簇的影响。n原位生成。使用复杂的[Me 4 Fe] Li 2的对照实验证实了这一解释。
Catalytic 1,3-Difunctionalization via Oxidative C–C Bond Activation
作者:Steven M. Banik、Katrina M. Mennie、Eric N. Jacobsen
DOI:10.1021/jacs.7b05160
日期:2017.7.12
reagents and can engage a variety of substituted cyclopropane substrates. Analysis of crystal and solution structures of several of the products reveal the consistent effect of 1,3-difluorides in dictating molecular conformation. The generality of the 1,3-oxidation strategy is demonstrated through the catalytic oxidative ring-opening of cyclopropanes for the synthesis of 1,3-fluoroacetoxylated products
Polylithiumorganic compounds. Part 29: C,C Bond cleavage of phenyl substituted and strained carbocycles using lithium metal
作者:Adalbert Maercker、Kristian S. Oeffner、Ulrich Girreser
DOI:10.1016/j.tet.2004.06.105
日期:2004.9
The reaction of phenyl substituted cyclopropanes phenylcyclopropane and 1,1-diphenylcyclopropane, phenyl substituted bicyclobutanes 1-phenylbicyclobutane, 1-methyl-3-phenylbicyclobutane, 1-methyl-2,2-diphenylbicyclobutane, as well as phenyl substituted spiropentanes phenylspiropentane and 1,1-diphenylspiropentane with lithium metal or lithium di-t-butylbiphenyl (LiDBB) was investigated. Under suitable
methods that address the selective formation of (Z)-olefins. In such cases, specific catalysts (e. g., cross-metathesis)3 or modified anion stabilizing groups (e. g., Still-Gennari modification of Horner-Wadsworth-Emmonsolefination)4 are utilized. The Peterson olefination,2g, 2h on the other hand, allows for the stereoselective formation of either (E) or (Z)-olefins from the same starting material by a
介绍 碳-碳键形成反应是有机合成化学中的关键连接反应。其中,不饱和键(特别是烯烃)的立体选择性形成具有重要意义,因为它们参与天然产物、生物活性化合物和材料的合成。目前,实现立体选择性连接烯化的两种常用方法是烯烃交叉复分解1和阴离子稳定试剂与醛或酮的偶联2(图 1)。这些方法通常在温和的反应条件下进行,对官能团表现出良好的耐受性,并且主要产生( E )-构型的烯烃。然而,解决( Z )-烯烃的选择性形成的方法有限。在这种情况下,使用特定的催化剂(例如交叉复分解)3或改性阴离子稳定基团(例如Horner-Wadsworth-Emmons烯化的Still-Gennari改性)4 。另一方面,Peterson 烯化(2g,2h)允许通过反应后处理(酸性与碱性)的简单改变,从相同的起始材料立体选择性地形成( E)或(Z )-烯烃。 5然而,即使在这种情况下,原位生成的加合物 (顺/反)的立体选择性也反映在烯化反应的最终立体化学结果中。
A nickel-catalyzed carbozincation of aryl-substituted alkynes
The addition of dialkylzincs or diphenylzinc to substituted phenylacetylenes in the presence of catalytic amounts of Ni(acac)(2) in THF : NMP mixtures produces syn-carbozincation products with good to excellent regio-and stereoselectivity. After quenching with an electrophile (iodine, acyl chloride, allyl bromide) tetrasubstituted olefines are obtained in good to satisfactory yields. An intramolecular version of the reaction is possible using a terminal triple bond bearing an iodine at a remote position. More substituted iodo-alkynes furnish only reductive elimination products. An application to a stereoselective synthesis of (Z)-tamoxifen (Z: E > 99: 1) has been developed. (C) 1998 Elsevier Science Ltd. All rights reserved.