Domino 6-Endo-dig Cyclization/Halogenation Reactions: Three-Component Synthesis of 1,3-Disubstituted 4-Haloimidazo[1,2-a:4,5-C′]dipyridines

A regiocontrolled 6-endo-dig cyclization of 3-ethynylimidazo[1,2-a]pyridine-2-carbonitriles promoted by Grignard reagent in the presence of iodine has been developed. We optimized the reaction conditions to allow the straightforward synthesis of 1,3-disubstituted 4-iodoimidazo[1,2-a:4,5-c]dipyridines. Finally, the reactivity of the 4-iodo position toward various metal-catalyzed coupling reactions (Suzuki-Miyaura, Sonogashira, etc.) or cyanation was successfully evaluated.