Photocatalytic Sequential Dimerization and Skeletal Rearrangement of Quinolines: Facile Synthesis of Indole–Methylquinoline Hybrids

Skeletal editing of aromatic heterocycles represents a promising strategy for interconverting various aromatic heterocycles, facilitating rapid alterations in skeletal structures while conserving the essential features of the original framework. Despite progress in this field, the ring contraction of quinolines via a radical anion intermediate continues to pose significant challenges. In this study, we present a visible-light photocatalytic sequential dimerization and skeletal rearrangement of quinoline skeletons through reductive activation, efficiently constructing indole–methylquinoline hybrids. This reaction showcases a good functional group tolerance, a wide substrate scope, and mild reaction conditions. A diverse array of quinoline derivatives, including C2-aryl, C2-carbonyl, and C2-alkyl substituted quinolines, can participate in this transformation smoothly. Mechanistic investigations reveal that the single-electron-transfer (SET) reduction of quinolines to generate quinoline radical anions is a critical step in this process.