Rrapi Marie, Batsika Charikleia S, Nikitas Nikolaos F, Tappin Nicholas D C, Triandafillidi Ierasia, Renaud Philippe, Kokotos Christoforos G
Laboratory of Organic Chemistry, Department of Chemistry, National and Kapodistrian University of Athens, Panepistimiopolis, Athens, 15771, Greece.
Department of Chemistry, Biochemistry, and Pharmaceutical Sciences, University of Bern, Freiestrasse 3, CH-3012, Bern, Switzerland.
Chemistry. 2024 Apr 11;30(21):e202400253. doi: 10.1002/chem.202400253. Epub 2024 Feb 22.
Light-mediated processes have received significant attention, since they have re-surfaced unconventional reactivity platforms, complementary to conventional polar chemistry. γ-Lactones and cyclopropanes are prevalent moieties, found in numerous natural products and pharmaceuticals. Among various methods for their synthesis, light-mediated protocols are coming to the spotlight, although these are contingent upon the use of photoorgano- or metal-based catalysts. Herein, we introduce a novel photochemical activation of iodo-reagents via the use of cheap sodium ascorbate or ascorbic acid to enable their homolytic scission and addition onto double bonds. The developed protocol was applied successfully to the formal [3+2] cycloaddition for the synthesis of γ-lactones, traditional atom transfer radical addition (ATRA) reactions and the one-pot two-step conversion of alkenes to cyclopropanes. In all cases, the desired products were obtained in good to high yields, while the reaction mechanism was thoroughly investigated. Depending on the nature of the iodo-reagent, a halogen or a hydrogen-bonded complex is formed, which initiates the process.
光介导的过程受到了广泛关注，因为它们重新展现了非常规的反应活性平台，是传统极性化学的补充。γ-内酯和环丙烷是众多天然产物和药物中普遍存在的部分。在它们的各种合成方法中，光介导的方法正成为焦点，尽管这些方法依赖于使用光有机或金属基催化剂。在此，我们介绍了一种通过使用廉价的抗坏血酸钠或抗坏血酸对碘试剂进行新型光化学活化，以实现其均裂并加成到双键上的方法。所开发的方法成功应用于γ-内酯合成的形式上的[3 + 2]环加成反应、传统的原子转移自由基加成（ATRA）反应以及烯烃一锅两步转化为环丙烷的反应。在所有情况下，均以良好至高收率获得了所需产物，同时对反应机理进行了深入研究。根据碘试剂的性质，会形成卤素或氢键络合物，从而引发反应过程。
