Grignard reagent-promoted 6- endo-dig cyclization: instantaneous synthesis of original dipyrido[1,2- a:3′,4′- d]imidazole

Abstract

Dipyrido[1,2- a:3′,4′- d]imidazole derivatives can be readily synthetized from various 3-alkyne-2-cyanoimidazo[1,2- a]pyridines via an efficient Grignard reagent-promoted 6- endo-dig cyclization of nitrile to alkynes. A previous optimization of the Sonogashira coupling reaction at C(3) of the 2-cyanoimidazo[1,2- a]pyridine was necessary as this coupling reaction is known to be largely influenced by the nature of the 2-substituent.