Unusual Chemodivergence in the Amination of 2-Chloro-1,10-Phenanthroline with Di- and Polyamines: Comparison of the Pd-Catalyzed and Catalyst-Free Pathways

The amination of 2-chloro-1,10-phenanthroline with various alkylamines and diamines was investigated. The Pd-catalyzed reaction and catalyst-free protocols were shown to lead to different products. Catalyst-free amination of this substrate using aliphatic amines yielded secondary phenanthrolin-2-yl amines in 40–80% yields. The Pd-catalyzed reaction afforded tertiary di(phenanthrolin-2-yl)amines even in the presence of excess amine. This allows for the synthesis of unsymmetric N,N-diheteroaryl-substituted diamines in 44–50% yields with good selectivity. Using 2-bromo-1,10-phenanthroline leads to an increase in their yields (62–91%). We have also demonstrated the possibility to obtain N,N,N′,N′-tetraheteroarylated derivatives of diamines in yields of up to 55%. Thus obtained compounds can serve as promising ligands for various applications.