Michel Elena, Grieser Fabian F, Mackenroth Alexandra V, Schukin Michael, Krämer Petra, Tahir Shaista, Rominger Frank, Rudolph Matthias, Hashmi A Stephen K
Institut für Organische Chemie, Heidelberg University, Im Neuenheimer Feld 270, 69120, Heidelberg, Germany.
Chemistry Department, Faculty of Science, King Abdulaziz University, Jeddah, 21589, Saudi Arabia.
Angew Chem Int Ed Engl. 2023 Oct 16;62(42):e202309274. doi: 10.1002/anie.202309274. Epub 2023 Sep 8.
The chemistry of alkynyl triazenes is an emerging field for organic chemists and especially acid-induced nucleophilic functionalizations, either directly, or after a prior reaction towards aromatic triazenes under extrusion of nitrogen, paved the way for fruitful strategies. In contrast, the chemical behavior of alkynyl triazenes upon irradiation with light is still unknown. Herein we present the first photoactivation of alkynyl triazenes that triggers an uncommon reactivity pattern involving the cleavage of the N1-N2 bond of the triazene moiety resulting in a unique approach to cyanocarbenes from a readily available, stable, and insensitive precursor. This allows to access various nitrile compounds without the use of a toxic cyanating agent by exploiting the reactivity pattern of carbenes. By variation of the reaction conditions and light sources, different substitution patterns can be obtained selectively in good yields under mild and metal-free conditions, thus introducing the alkynyl triazene unit as a photo accessible methylene nitrile synthon. Using this synthon, subclasses like α-alkoxynitriles, α-aminonitriles and α-cyanohydrazones become easily available. These exhibit synthetically valuable substitution patterns for the synthesis of pharmaceuticals, intermediates for total synthesis and amino acid synthesis.
炔基三氮烯的化学性质对有机化学家来说是一个新兴领域，尤其是酸诱导的亲核官能团化反应，无论是直接进行，还是在氮气挤出条件下先与芳基三氮烯反应后进行，都为富有成效的策略铺平了道路。相比之下，炔基三氮烯在光照下的化学行为仍然未知。在此，我们首次报道了炔基三氮烯的光活化反应，该反应引发了一种不寻常的反应模式，涉及三氮烯部分的N1-N2键断裂，从而从一种易于获得、稳定且不敏感的前体生成氰基卡宾的独特方法。通过利用卡宾的反应模式，这使得无需使用有毒的氰化剂就能获得各种腈化合物。通过改变反应条件和光源，可以在温和且无金属的条件下以良好的产率选择性地获得不同的取代模式，从而将炔基三氮烯单元引入为一种可光活化的亚甲基腈合成子。使用这种合成子，α-烷氧基腈、α-氨基腈和α-氰基腙等亚类变得容易获得。这些化合物在药物合成、全合成中间体和氨基酸合成中展现出具有合成价值的取代模式。
