Ru(II)-Catalyzed Synthesis of Fused Imidazo[1,2-<i>a</i>]pyridine-chromenones and Methylene-Tethered Bis-imidazo[1,2-<i>a</i>]pyridines and Regioselective O-Acetoxylation of Imidazo[1,2-<i>a</i>]pyridines

Abstract

Herein, we disclose an unprecedented protocol via ruthenium-catalyzed annulation for the synthesis of 6 H -chromeno[4′,3′:4,5]imidazo[1,2- a ]pyridin-6-one, and functionalized 2-(3-formylimidazo[1,2- a ]pyridin-2-yl)phenyl acetate has been revealed by intramolecular chelation-assisted C–H activation. Additionally, a one-pot approach for creating bis(2-phenylimidazo[1,2- a ]pyridin-3-yl)methane (BIP) has been realized through ruthenium catalysis with the use of formic acid. This method was used in gram-scale synthesis of BIP and step-economical late-stage functionalization of a marketed drug, zolimidine, in good yield.