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

Abstract

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.