Copper‐Catalyzed Alkoxy Radical‐Mediated Ring‐Expansion/C(sp ³ )–N Coupling of Hemiketal Peroxides with <i>N</i> ‐Nucleophiles: A Route to Functionalized Macrolactones

A copper‐catalyzed alkoxy radical‐mediated ring‐expansion/C(sp 3 )–N coupling of hemiketal peroxides with N ‐nucleophiles has been developed. This protocol allows the construction of functionalized medium‐sized and macrolactones under mild redox‐neutral conditions, exhibiting broad substrate scope and good functional group tolerance. The ring‐expansion amination proceeds efficiently with diverse nitrogen nucleophiles, including amides, sulfamides, indoles, indazoles, and pyrazoles, providing a concise and step‐economical strategy for the synthesis of structurally diverse amino‐substituted lactones. Control studies reveal that the nature of the leaving group in hemiketal peroxides is crucial for the success of this reaction.