Radical Dearomatization of Indoles with N-Aminopyridinium Salts for the Synthesis of Indolinimines.

Indolinimine motifs are widespread in biologically active natural products and pharmaceuticals. Despite their significance, the direct one-step synthesis of indolinimines from indoles under mild conditions remains a formidable challenge. Herein, we report a visible light-promoted radical dearomatization of indoles using readily available N-aminopyridinium salts as nitrogen-centered radical precursors. This protocol enables a mild, one-step synthesis of diverse indolinimine derivatives with good to excellent yields, featuring a broad substrate scope, excellent functional group compatibility, and operational simplicity. Mechanistic studies revealed a pathway involving amidyl radical addition to indoles, followed by dearomatization and an intramolecular cascade transformation. This work presents a green and efficient strategy for constructing a valuable indolinimine skeleton, offering potential applications in medicinal chemistry and organic synthesis.