Hydrogen Bonding Interaction Enabled Ru(III)‐Catalyzed Synthesis of (Multi)‐Substituted Pyridines

Abstract

AbstractHerein, we report a cost‐effective synthesis of various multi‐substituted pyridine derivatives, especially 2‐aryl pyridines, using secondary alcohols and 1,3‐diol as the primary feedstock with ammonium acetate serving as nitrogen donor, catalyzed by a new well‐defined singlet mono‐radical Ru(III)‐catalyst featuring a cyclopentadienyl group, one PPh3, and a redox‐active scaffold −N1‐(2‐aminophenyl)benzene‐1,2‐diamine having a pendant ‐NH2 arm. The ‐NH2 arm of the catalyst facilitates the generation of the critical reactive intermediates by enhancing the electrophilicity of the carbonyl carbon center of the diols or diketones by forming hydrogen bonds, making it more catalytically effective over the similar other Ru‐catalysts having no pendant ‐NH2 arm. The Ru‐catalyst also functionalizes 2‐aryl pyridine moieties with different coupling partners, such as aryl iodides, terminal alkynes, and styrene derivatives at the o‐position of the phenyl ring.