Conen Peter, Nickisch Roman, Meier Michael A R
Institute of Organic Chemistry (IOC), Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131, Karlsruhe, Germany.
Institute of Biological and Chemical Systems - Functional Molecular Systems (IBCS-FMS), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344, Eggenstein-Leopoldshafen, Germany.
Commun Chem. 2023 Nov 18;6(1):255. doi: 10.1038/s42004-023-01058-2.
Tetraphenylethylenes (TPEs) are well-known for their aggregation-induced emission properties. The synthesis of TPE derivatives, as well as other highly substituted olefins, generally requires the use of hazardous reagents, such as metalorganic compounds, to overcome the high activation energies caused by the sterically congested double bond. Herein, we present an efficient and metal-free procedure for the synthesis of tetraarylethylenes via alkylidene-homocoupling of N-tosylhydrazones, derived from readily available benzophenones, in excellent yields. The method relies only on cheap and benign additives, i.e. elemental sulfur and potassium carbonate, and easily competes with other established procedures in terms of scope, yield and practicability. A mechanistic study revealed a diazo compound, a thioketone and a thiirane as key intermediates in the pathway of the reaction. Based on this, a modified method, which allows for selective alkylidene-cross-coupling, generating a broader scope of tri- and tetrasubstituted olefins in good yields, is showcased as well.
四苯乙烯（TPEs）因其聚集诱导发光特性而闻名。TPE衍生物以及其他高度取代的烯烃的合成通常需要使用危险试剂，如金属有机化合物，以克服由空间位阻双键引起的高活化能。在此，我们展示了一种高效且无金属的方法，通过由易得的二苯甲酮衍生的N-对甲苯磺酰腙的亚烷基均偶联反应来合成四芳基乙烯，产率优异。该方法仅依赖于廉价且良性的添加剂，即元素硫和碳酸钾，并且在反应范围、产率和实用性方面很容易与其他既定方法相媲美。机理研究揭示了重氮化合物、硫酮和硫杂环丙烷是该反应途径中的关键中间体。基于此，还展示了一种改进方法，该方法允许选择性亚烷基交叉偶联，以良好的产率生成更广泛的三取代和四取代烯烃。
