Two new catalytic systems for hydrogen‐atom transfer (HAT) catalysis involving the N−H bonds of titanocene(III) complexes with pendant amide ligands are reported. In a monometallic system, a bifunctional catalyst for radical generation and reduction through HAT catalysis depending on the coordination of the amide ligand is employed. The pendant amide ligand is used to activate Crabtree's catalyst to
Visible-light-driven spirocyclization of epoxides <i>via</i> dual titanocene and photoredox catalysis
作者:Shuangjie Lin、Yuqing Chen、Fusheng Li、Caizhe Shi、Lei Shi
DOI:10.1039/c9sc05601g
日期:——
We describe the synergistic utilization of titanocene/photoredox dual catalysis driven by visible light for the radical opening/spirocyclization of easily accessible epoxyalkynes. This environmentally benign process uses the organic donor–acceptor fluorophore 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) as a photocatalyst and Hantzsch ester (HE) as an electron donor instead of stoichiometric
我们描述了由可见光驱动的二茂钛/光氧化还原双重催化的协同利用,用于容易获得的环氧炔烃的自由基打开/螺环化。这种对环境无害的过程使用有机供体-受体荧光团2,4,5,6-四(9 H-咔唑-9-基)间苯二甲腈(4CzIPN)作为光催化剂,汉茨酯(HE)作为电子给体,而不是化学计量的金属还原剂。光催化条件显示了具有螺环全碳四元立体中心的特权和合成挑战性螺环的合成具有极高的反应活性。循环伏安法(CV)研究表明Cp 2 Ti III Cl是催化活性物质。
Coupling Titanium and Chromium Catalysis in a Reaction Network for the Reprogramming of [BH<sub>4</sub>]<sup>−</sup> as Electron Transfer and Hydrogen Atom Transfer Reagent for Radical Chemistry
Reprogramming the typical hydride character of borohydrides to a stepwise electron and H-atom transferreagent allows epoxide reduction, C−C bond formation and regiodivergent epoxide opening in an unusual manner by avoiding SN2-type reactivity of [BH4]−. The readily available Li[BH4] is used as sole stoichiometric reagent.
通过有效耦合地球上储量丰富的两种金属钛和铬,从催化循环到催化球。将硼氢化物的典型氢化物特征重新编程为逐步电子和氢原子转移试剂,通过避免 [BH 4 ] -的 S N 2 型反应性,可以以不寻常的方式进行环氧化物还原、CC 键形成和区域发散环氧化物打开。容易获得的Li[BH 4 ]被用作唯一的化学计量试剂。
Radical Cyclizations Terminated by Ir-Catalyzed Hydrogen Atom Transfer
作者:Andreas Gansäuer、Matthias Otte、Lei Shi
DOI:10.1021/ja109362m
日期:2011.1.26
A system for coupling catalytic radical cyclization and Ir-catalyzed hydrogen atom transfer (HAT) is described. It is essential that the HAT catalyst activates H(2) quickly and is not a hydrogenation catalyst. Vaska's complex was found to fulfill both purposes efficiently.
Tungsten-Promoted [3+2]- and [3+3]-Cycloaddition of Epoxides with Alkynes. A Facile Enantiospecific Synthesis of Bicyclic Lactones
作者:Reniguntala J. Madhushaw、Chien-Le Li、Kuo-Hui Shen、Chu-Chen Hu、Rai-Shung Liu