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. © 2011 Elsevier Ltd. All rights reserved.