State Key Laboratory of Physical Chemistry of Solid Surfaces, Key Laboratory of Chemical Biology of Fujian Province, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen361005, P. R. China.
Green Catalysis Center and College of Chemistry, Zhengzhou University, Zhengzhou, Henan450001, P. R. China.
J Am Chem Soc. 2022 Feb 9;144(5):2343-2350. doi: 10.1021/jacs.1c12762. Epub 2022 Feb 1.
Cyclopropane is a prevalent structural unit in natural products and bioactive compounds. While the transition metal-catalyzed alkene cyclopropanation of functionalized compounds such as α-diazocarbonyl derivatives has been well established and provides straightforward access to cyclopropanes, cyclopropanation directly from the more stable and simpler methylene compounds has remained an unsolved challenge despite the highly desirable benefits of minimal prefunctionalization and increased operational safety. Herein we report an electrocatalytic strategy for the cyclopropanation of active methylene compounds, employing an organic catalyst. The method shows a broad substrate scope and excellent scalability, requires no metal catalyst or external chemical oxidant, and provides convenient access to several types of cyclopropane-fused heterocyclic and carbocyclic compounds. Mechanistic investigations suggest that the reactions proceed through a radical-polar crossover process to form the two new carbon-carbon bonds in the nascent cyclopropane ring.
环丙烷是天然产物和生物活性化合物中常见的结构单元。虽然过渡金属催化的官能化化合物（如α-重氮羰基衍生物）的烯烃环丙烷化反应已经得到很好的建立，并为环丙烷提供了直接途径，但直接从更稳定和更简单的亚甲基化合物进行环丙烷化仍然是一个未解决的挑战，尽管最小预官能化和提高操作安全性具有非常理想的好处。在此，我们报告了一种使用有机催化剂的电催化策略，用于活性亚甲基化合物的环丙烷化。该方法具有广泛的底物范围和出色的可扩展性，不需要金属催化剂或外部化学氧化剂，并且可以方便地获得多种类型的环丙烷稠合杂环和碳环化合物。机理研究表明，反应通过自由基-极性交叉过程进行，在新形成的环丙烷环中形成两个新的碳-碳键。
