Photochemical generation of radicals from alkyl electrophiles using a nucleophilic organic catalyst
作者:Bertrand Schweitzer-Chaput、Matthew A. Horwitz、Eduardo de Pedro Beato、Paolo Melchiorre
DOI:10.1038/s41557-018-0173-x
日期:2019.2
extensively use free radical reactivity for applications in organic synthesis, materials science, and life science. Traditionally, generating radicals requires strategies that exploit the bond dissociation energy or the redox properties of the precursors. Here, we disclose a photochemical catalytic approach that harnesses different physical properties of the substrate to form carbon radicals. We use a nucleophilic
化学家在有机合成,材料科学和生命科学中广泛使用自由基反应性。传统上,产生自由基需要利用键解离能或前体的氧化还原特性的策略。在这里,我们公开了一种光化学催化方法,该方法利用了基材的不同物理特性来形成碳自由基。我们使用亲核性的二硫代氨基甲酸酯阴离子催化剂,配以量身定制的发色单元,以通过S N 2途径活化烷基亲电体。所得的吸收光子的中间体在由可见光诱导的均相裂解时提供自由基。此催化性S N基于2的策略利用了离子化学的基本机理过程,可以从各种底物中获得与经典自由基生成策略不兼容或惰性的开壳中间体的访问权限。我们还描述了该方法温和的反应条件和较高的官能团耐受性如何有利于开发C–C键形成反应,简化市售药物的制备,生物相关化合物的后期精制以及对映选择性自由基催化。
A visible-light mediated three-component radical process using dithiocarbamate anion catalysis
作者:Sara Cuadros、Matthew A. Horwitz、Bertrand Schweitzer-Chaput、Paolo Melchiorre
DOI:10.1039/c9sc00833k
日期:——
We report a photoinduced three-component radicalprocess, which couples readily available alkyl chlorides, maleimides, and heteroaromatic fragments to rapidly generate complex chiral products with high diastereocontrol. This method generates radicals via an SN2-based photochemical catalytic mechanism, which is not reliant on the redox properties of the precursors. It therefore grants access to open-shell
我们报告了光诱导的三组分自由基过程,该过程耦合随时可用的烷基氯化物,马来酰亚胺和杂芳族片段,以快速生成具有高非对映异构控制性的复杂手性产物。该方法通过基于S N 2的光化学催化机理产生自由基,这不依赖于前体的氧化还原性质。因此,它可以从底物中获得与经典自由基产生策略不相容或惰性的底壳中间体。该过程的氧化还原中性条件使其对氧化还原敏感的底物具有耐受性,并允许在级联产物中安装多个生物学相关的杂环。
A novel class of nickel(<scp>ii</scp>) complexes containing selenium-based bidentate ligands applied in ethylene oligomerization
作者:Lucielle C. Dresch、Bruno B. de Araújo、Osvaldo de L. Casagrande、Rafael Stieler
DOI:10.1039/c6ra18987c
日期:——
A series of nickel(II) complexes [NiBr2(N^Se)2] (Ni1–Ni5) based on bidentate N^Se ligands were prepared by reacting arylselenyl–pyrazolyl ligands (L1–L5) with NiBr2(DME) (DME = 1,2-dimethoxyethane). All Ni complexes were characterized by IR spectroscopy, elemental analysis, high-resolution mass spectrometry (HRMS), and by X-ray crystallography for Ni4. X-ray crystallographic analyses of Ni4 revealed
mutually trans positions. Upon activation with methylaluminoxane (MAO), all nickel complexes were able to oligomerize ethylene with turnover frequencies (TOFs) varying from 5.0 to 16.6 × 103 (mol ethylene) (mol Ni)−1 h−1 producing selectively 1‐butene (91.0–95.5 wt%). The substitution on the pyrazolyl group and the length of the backbone chain play a significant role in the catalytic activity. The use of
In Situ Formation of Semichelating Ligands: A Strategy for Tuning the Magnetic Coupling in Azide-Bridged Copper(II) Complexes
作者:Wen-Bo Shi、Ai-Li Cui、Hui-Zhong Kou
DOI:10.1002/cplu.201300304
日期:2014.2
corresponding alcohols without azide. For complexes 1-5, the oxygen atom of the ether ligands is located at the Jahn-Teller axis of CuII with the long CuO separations of 2.377(3)-2.830(3) Å. The nitrogen atoms of bridging azides are located in the equatorial or basal planes of CuII ions, favoring strong magnetic coupling. The Cu-Nazido -Cu bridging angles in complexes 1-3 are 98.8(2)°-101.6(1)°, leading