Efficient Synthesis of 1‐Chloroimidazo[1,2‐a:4,5‐c']dipyridines, Versatile Synthons for Position‐1 Functionalisation with Various Reagents

Imidazo[1,2-a:4,5-c']dipyridines are remarkable skeletons in the field of medicinal chemistry. This article presents the synthesis of 1-chloroimidazo[1,2-a:4,5-c']dipyridines, versatile synthons to functionalize at position-1. Several examples of further reactions are presented, including Suzuki–Miyaura and Sonogashira cross-couplings, nucleophilic aromatic substitutions, and cyanation or reduction of the CCl bond. 41 new molecules have been synthesized by these methods.

In this work, the goal is to develop a versatile synthetic pathway to functionalize position-1 of the imidazo[1,2-a;4,5-c']dipyridine core. For this purpose, the synthesis of 1-chloroimidazo[1,2-a;4,5-c']dipyridines via a novel synthetic pathway starting from imidazo[1,2-a]pyridines conveniently substituted with a carboxamide at position-2 and an alkyne at position-3 is described. This pathway involves a 6-endo-dig cyclization leading to the 3-alkyl-1-hydroxyimidazo[1,2-a;4,5-c']dipyridine intermediates. The 1-chloroimidazo[1,2-a;4,5-c']dipyridines are then obtained via a dehydrochlorination. Further, their reactivity is evaluated, particularly in palladium-catalyzed couplings and nucleophilic aromatic substitutions.

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