基于氮杂环卡宾弱相互作用的光促使的自由基偶联反应

虽然氮杂环卡宾作为有机小分子催化剂在催化反应中取得了极大的成功。但是，其利用弱相互作用的反应至今仍未实现。最近，光活性电子给体-受体（electron donor-acceptor，EDA）复合物已经发展成为在可见光引发下产生自由基的有效工具。但是，目前其反应机理仍不明确，并且仅有特定的化合物才可以形成EDA复合物，这极大地限制了该策略在光促反应中的应用。本项目拟通过卡宾的弱相互作用实现光促使的自由基-自由基偶联反应，包括新型可控的碘化反应，以及进一步的串联反应，为生物活性分子的合成提供新的合成方法和策略。该氮杂环卡宾稳定EDA复合物的方法及对光活化过程的机理理解可以丰富基于EDA复合物的光化学，并激发氮杂环卡宾催化的新发展。

While there is a growing interest in harnessing the applications of N-heterocyclic carbenes (NHCs) as organocatalysts, their weak interaction is rather unexplored. The photoactive electron donor-acceptor (EDA) complex has recently emerged as a useful tool for the generation of radicals in visible light-triggered reactions. However, the way that EDA complex generated radicals under the excitation of visible light is the lack of understanding and their current applications mainly rely on selected moleculars. By utilizing the weak interaction of NHC, we herein propose to develop the photochemical radical-radical cross-couplings, including novel and controllable iodination reactions, and the related cascade reactions. The mild and metal-free conditions of the reaction could render the method highly attractive for the synthesis of a range of bioactive compounds. The unveiling of the way of NHC in stabilizing EDA complexes and the mechanistic understanding of the photoactivation process could enrich the photochemistry of EDA complexes and inspire the new development of NHC catalysis.