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.