Visible-Light-Mediated Ruthenium-Catalyzed para-Selective Alkylation of Unprotected Anilines

Anilines are important moieties in organic chemistry, pharmaceuticals, and materials science. Although para-selective functionalization of anilides and tertiary anilines is well established, unprotected anilines have posed a challenge. Herein, we report visible-light-mediated Ru(II)-catalyzed para-alkylation of anilines. The distinct Ru(II)–aniline complex enabled the reaction to proceed with extremely high efficiency (2 h) under mild conditions. The good functional group tolerance allowed late-stage functionalization and even aggregation-induced emission luminogen labeling of natural products and drugs. A mechanistic investigation suggests that the Ru(II)–aniline complex is crucial for both triggering the reaction and controlling the para-selectivity.