UV photolysis of powdered crystals of several aryl azides at cryogenic temperatures afforded azo compounds predominantly. In the cases of p-(N-methylacetamido)phenyl azide and 2-azidobiphenyl, a CH insertion product or a carbazole was formed, competing with azo formation. These products can be considered to be formed through topotactic processes when the crystal structures are taken into account. The arylnitrenes generated in the azide crystals were monitored by ESR spectroscopy; they turned out to have extremely long half life-times, compared with those in the gas phase or in solution. Such high kinetic stabilities are ascribed to the inert environment around the generated nitrenes. The decay process of arylnitrenes in the initial stage obeyed a pseudo-first order kinetics; activation parameters were evaluated by Arrhenius plots. The activation enthalpies and entropies indicate that the diffusional processes of arylnitrenes may be the vital factors determining the kinetic stability and the product distribution in the crystalline environment.
Sasaki; Izuoka; Sugawara, Molecular Crystals and Liquid Crystals Science and Technology, Section A: Molecular Crystals and Liquid Crystals, 1996, vol. 276-277, # pt 1-2, p. 17 - 22
作者:Sasaki、Izuoka、Sugawara
DOI:——
日期:——
Catalytic Azoarene Synthesis from Aryl Azides Enabled by a Dinuclear Ni Complex
作者:Ian G. Powers、John M. Andjaba、Xuyi Luo、Jianguo Mei、Christopher Uyeda
DOI:10.1021/jacs.8b00503
日期:2018.3.21
machines and biologically active compounds. Here, we report a catalytic nitrene dimerization reaction that provides access to structurally and electronically diverse azoarenes. The reaction utilizes arylazides as nitrene precursors and generates only gaseous N2 as a byproduct. By circumventing the use of a stoichiometric redox reagent, a broad range of organic functional groups are tolerated, and common
偶氮芳烃是有价值的发色团,已被广泛用作分子机器和生物活性化合物中的光开关元件。在这里,我们报告了一种催化氮烯二聚反应,该反应提供了结构和电子上多样化的偶氮芳烃。该反应使用芳基叠氮化物作为氮烯前体并仅产生气态 N2 作为副产物。通过避免使用化学计量氧化还原试剂,可以容忍广泛的有机官能团,并且避免了当前方法的常见副产物。发现具有 Ni-Ni 键的催化剂相对于仅包含单个 Ni 中心的催化剂具有独特的效果。描述了这种核效应的机械起源。