Stable, Yet Highly Reactive Nonclassical Iron(II) Polyhydride Pincer Complexes: <i>Z</i>-Selective Dimerization and Hydroboration of Terminal Alkynes
作者:Nikolaus Gorgas、Luis G. Alves、Berthold Stöger、Ana M. Martins、Luis F. Veiros、Karl Kirchner
DOI:10.1021/jacs.7b05051
日期:2017.6.21
polyhydride complexes containing tridentate PNP pincer-type ligands is described. These compounds of the general formula [Fe(PNP)(H)2(η2-H2)] exhibit remarkable reactivity toward terminalalkynes. They efficiently promote the catalytic dimerization of aryl acetylenes giving the corresponding conjugated 1,3-enynes in excellent yields with low catalyst loadings. When the reaction is carried out in the presence
描述了含有三齿 PNP 钳型配体的非经典铁 (II) 氢化物配合物的合成、表征和催化活性。这些通式[Fe(PNP)(H)2(η2-H2)]的化合物对末端炔表现出显着的反应性。它们有效地促进芳基乙炔的催化二聚化,以极低的催化剂负载量以优异的产率得到相应的共轭 1,3-烯炔。当反应在频哪醇硼烷存在下进行时,得到乙烯基硼酸酯。这两个反应都在温和的条件下进行,并且具有高度的化学选择性、区域选择性和立体选择性,Z 选择性高达 99%。
Ligand mediated iron catalyzed dimerization of terminal aryl alkynes: scope and limitations
in toluene at 145 °C for 2 h to give the corresponding head-to-head dimers in good to excellent yields (54 to 99%) with high E-selectivity (67 : 33 to 83 : 17 E/Z). Both strongly electron-donating and electron-withdrawing groups are compatible with this procedure. The bidentate phosphine (dppe) ligand exhibits better catalytic activity than the bidentate amine (DMEDA). The aliphatic acetylene fails to
在DMEDA或dppe的存在下,使用FeCl 3和KO t Bu实现了末端芳基炔烃的区域选择性二聚,以产生共轭烯炔。反应在145°C的甲苯中平稳进行2小时,以高至E的选择性(67:33至83:17 E / Z)以良好至优异的收率(54%至99%)得到相应的头对头二聚体)。强供电子基团和吸电子基团均与该程序相容。双齿膦(dppe)配体显示出比双齿胺(DMEDA)更好的催化活性。脂肪族乙炔无法在该催化体系下反应,这表明叔丁醇钾通过阳离子-π相互作用和pi-pi相互作用激活了芳基乙炔的共轭体系。自由基抑制剂(galvinoxyl或TEMPO)可完全抑制反应。使用FeCl 2代替FeCl 3作为催化剂,仅苯基乙炔以良好的收率提供了相应的头对头二聚体。FeCl 3催化芳基炔烃和FeCl 2的二聚反应的机理途径 已经提出了苯基乙炔的催化二聚作用。
Z-Selective Alkyne Functionalization Catalyzed by a <i>trans</i>-Dihydride N-Heterocyclic Carbene (NHC) Iron Complex
作者:Subhash Garhwal、Natalia Fridman、Graham de Ruiter
DOI:10.1021/acs.inorgchem.0c02057
日期:2020.10.5
The Z-selective functionalization of terminalalkynes is a useful transformation in organic chemistry and mainly catalyzed by noble metals. Here, we present the Z-selective hydroboration of terminalalkynes catalyzed by a stable trans-dihydride iron complex [(PCNHCP)Fe(H)2N2)] (2). Overall, the reaction occurs at room temperature and provides near quantitative yields of the Z-vinylboronate ester. Interestingly
末端炔烃的Z选择性官能化是有机化学中的有用转变,主要由贵金属催化。在这里,我们介绍了由稳定的反式-二酐铁络合物[(PC NHC P)Fe(H)2 N 2)](2)催化的末端炔烃的Z选择性氢硼化。总的来说,该反应在室温下发生,并提供接近定量的Z-乙烯基硼酸酯。有趣的是,相同的催化剂也可以提供E-在稍微升高的温度(50°C)下加热反应混合物,生成-乙烯基硼酸酯。但是,如果该反应是在不存在HBpin的情况下进行的,则会观察到快速的Z选择性炔烃二聚化,这将在本报告中进一步讨论。
<i>Z</i>-Selective (Cross-)Dimerization of Terminal Alkynes Catalyzed by an Iron Complex
作者:Orestes Rivada-Wheelaghan、Subrata Chakraborty、Linda J. W. Shimon、Yehoshoa Ben-David、David Milstein
DOI:10.1002/anie.201601382
日期:2016.6.6
Efficient iron‐catalyzed homocoupling of terminal alkynes and cross‐dimerization of aryl acetylenes with trimethylsilylacetylene is reported. The complex [Fe(H)(BH4)(iPr‐PNP)] (1) catalyzed the (cross‐)dimerization of alkynes at room temperature, with no need for a base or other additives, to give the corresponding dimerized products with Z selectivity in excellent yields (79–99 %).
Dimerization of aryl alkynes by Grubbs-Hoveyda complex: investigation of factors affecting the efficiency of the process based on experimental and theoretical approaches
slight excess of triphenylphosphine was found as an efficient catalyst for the synthesis of 1,4-disubstituted enynes with preference for head-to-head coupling and Z-selectivity form in the dimerization of various terminal aryl alkynes. Selective product formation was affected by the steric and the electronic properties of the phosphine used as well as the substituents of the alkynes. In order to shed