美国宾夕法尼亚州立大学Ramesh Giri团队报道了光敏O2通过活性亚甲基化合物实现分子间烯烃环丙烷化。相关研究成果发表在2023年8月4日出版的国际学术期刊《科学》。

环丙烷是许多临床前、临床和商业药物以及天然产品的关键特征。合成它们最多产的技术是烯烃与重氮烷烃的金属催化反应，重氮烷烃是一种高能试剂，需要严格的安全预防措施。寻找可替代的无害试剂仍然是一项持续的挑战。

该文中，研究人员报道了一种简单的光氧化还原催化未活化烯烃与活性亚甲基化合物的分子间环丙烷反应。反应在中性溶剂中在空气或氧气（O₂）下进行，具有由蓝色发光二极管光激发的光氧化还原催化剂和作为分子碘添加或由烷基碘化物原位生成的碘助催化剂。机理研究表明，光敏O₂在碳中心自由基的产生中起着至关重要的作用，无论是在烯烃中添加活性亚甲基化合物还是闭环。

附：英文原文

Title: Photosensitized O2 enables intermolecular alkene cyclopropanation by active methylene compounds

Author: Dhruba P. Poudel, Amrit Pokhrel, Raj Kumar Tak, Majji Shankar, Ramesh Giri

Issue&Volume: 2023-08-04

Abstract: Cyclopropanes are key features in many preclinical, clinical, and commercial drugs, as well as natural products. The most prolific technique for their synthesis is the metal-catalyzed reaction of an alkene with a diazoalkane, a highly energetic reagent requiring stringent safety precautions. Discovery of alternative innocuous reagents remains an ongoing challenge. Herein, we report a simple photoredox-catalyzed intermolecular cyclopropanation of unactivated alkenes with active methylene compounds. The reaction proceeds in neutral solvent under air or dioxygen (O2) with a photoredox catalyst excited by blue light-emitting diode light and an iodine co-catalyst that is either added as molecular iodine or generated in situ from alkyl iodides. Mechanistic investigations indicate that photosensitized O2 plays a vital role in the generation of carbon-centered radicals for both the addition of active methylene compounds to alkenes and the ring closure.

DOI: adg3209

Source: https://www.science.org/doi/full/10.1126/science.adg3209