Malhotra Vasu, Elvers Benedict J, Dolai Ramapada, Chrysochos Nicolas, Bandaru Siva Sankar Murthy, Gangber Tejaswinee, Britto Neethinathan Johnee, Krummenacher Ivo, Rajaraman Gopalan, Braunschweig Holger, Schulzke Carola, Jana Anukul
Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India.
Institut für Biochemie, Universität Greifswald, D-17489 Greifswald, Germany.
J Am Chem Soc. 2024 Oct 30;146(43):29481-29490. doi: 10.1021/jacs.4c08876. Epub 2024 Oct 19.
Herein, we report nickel(0)-catalyzed cross-coupling reactions of NHC/CAAC-based carbodicarbene (NHC = -heterocyclic carbene and CAAC = cyclic(alkyl)(amino)carbene) with different aryl chlorides, bromides, and iodides. The resulting aryl-substituted cationic carbodicarbene derivatives are prone to one-electron oxidation yielding radical-dications, which, depending on the aryl motif employed, follow different modes of radical-radical dimerization and constitute an entry point to carbon/nitrogen- and nitrogen/nitrogen-centered diradicaloids. Subsequently, this coupling strategy was strategically applied to the synthesis of -phenylene- and ,-biphenylene-bridged carbon/carbon-centered electron-deficient diradicaloids. The employed π-conjugated spacer plays a crucial role in determining the triplet population at room temperature by modulation of the singlet-triplet gap: EPR inactive for -phenylene vs EPR active for ,-biphenylene. Nearly two decades after the disclosure of carbodicarbenes as donor-stabilized atomic carbon equivalents by Tonner and Frenking in 2007, we demonstrate their cross-couplings with a series of aryl halides/dihalides and, based on this, developed a modular methodology for the systematic synthesis of various electron-deficient diradicaloids.
在此，我们报道了基于氮杂环卡宾/环烷基（氨基）卡宾（NHC = N - 杂环卡宾，CAAC = 环烷基（氨基）卡宾）的碳二卡宾与不同芳基氯、溴和碘的镍（0）催化交叉偶联反应。所得的芳基取代阳离子碳二卡宾衍生物易于发生单电子氧化生成自由基二价阳离子，根据所采用的芳基结构，它们遵循不同的自由基 - 自由基二聚化模式，并构成了通向以碳/氮和氮/氮为中心的双自由基类化合物的切入点。随后，这种偶联策略被策略性地应用于合成对亚苯基和 ， - 联亚苯基桥连的以碳/碳为中心的缺电子双自由基类化合物。所采用的π共轭间隔基在通过调节单重态 - 三重态能隙来确定室温下的三重态丰度方面起着关键作用：对亚苯基的电子顺磁共振（EPR）无活性，而对联亚苯基的EPR有活性。在2007年托纳和弗伦金将碳二卡宾作为供体稳定的原子碳等价物披露近二十年后，我们展示了它们与一系列芳基卤化物/二卤化物的交叉偶联，并在此基础上开发了一种模块化方法，用于系统合成各种缺电子双自由基类化合物。
