Copper-Catalyzed Ring Expansion of Cyclopropyl Ketones/Formation of N‑acyliminium/Hetero-[4 + 2]-Cycloaddition: A Route to Substituted Pentacyclic Isoindolin-1-one

A Cu-catalyzed three-component cascade cyclization among 2-formylbenzonitrile, cyclopropyl ketones, and diaryliodonium salts for the construction of fused isoindolin-1-one compounds is achieved. Pentacyclic isoindolinone derivatives could be obtained in moderate to good yields. The proposed mechanism involved a ring expansion of cyclopropyl ketones/formation of N-acyliminium/hetero-[4 + 2]-cycloaddition process.本研究成功实现了铜催化2-甲酰基苯甲腈、环丙基酮与二芳基碘鎓盐（diaryliodonium salts）之间的三组分串联环化反应，用于构建稠合异吲哚啉-1-酮（fused isoindolin-1-one）类化合物。该反应可获得中等至良好收率的五环异吲哚啉酮衍生物。所提出的反应机理包含环丙基酮的扩环、N-酰基亚胺正离子（N-acyliminium）的形成以及杂-[4+2]-环加成（hetero-[4 + 2]-cycloaddition）过程。