Transition-Metal-Free Access to 2-Subsituted Indolines from Indoles via Dearomative Nucleophilic Addition Using Two-Molecule Organic Photoredox Catalysts

Abstract

A Photoinduced dearomative nucleophilic addition to N-Boc indoles mediated by two-molecule organic photoredox catalysts such as phenanthrene and 1,4-dicyanobenzene with UV irradiation furnished 2-substituted indolines in moderate to quantitative yields. Hydroxide, alkoxide, and cyanide ions can be used as a nucleophile to provide 2-hydroxy, 2-alkoxy, and 2-cyanoindolines, respectively. Both electron-rich and -deficient indoles, including tryptophan derivatives, can be employed in the photoreaction to provide various indolines. This method provides transition-metal-free access to 2-subsituted indolines from indoles using organic photoredox catalysts under mild conditions.