An Approach to Quinoline-Fused Imidazopyridines via CDC of Ethers with Imidazopyridines under Metal-Free Conditions.

An NH4I-catalyzed cross-dehydrogenative coupling (CDC) reaction of ethers with imidazopyridine cascade cyclization under transition-metal-free conditions has been developed. Cheap, commercially available ethers were used as both reagents and solvents, and green aqueous H2O2 was used as an oxidizing agent. A series of substituents on 2-(2-aminoaryl) imidazo[1,2-a]pyridines were tolerated, and the reaction gave quinoline-fused imidazopyridines in moderate to good yields.