Ethyl 2-chloroimidazo[1,2-a]pyridine-3-carboxylate (2.00 g) was added to a solution of p-bromophenol (1.617 g) and NaH (0.427 g) in DMF (dry) (10 mL) at 100° C. The mixture was stirred at 100° C. under a dry atmosphere overnight. The reaction mixture was diluted with MeOH, and concentrated in vacuo. The residue was purified by column chromatography (silica gel, eluted with 0%-30% EtOAc in hexane) to give ethyl 2-(4-bromophenoxy)imidazo[1,2-a]pyridine-3-carboxylate (1.5 g) as a colorless solid and 2-(4-bromophenoxy)imidazo[1,2-a]pyridine (530 mg) as a colorless solid. The mixture of 2-(4-bromophenoxy)imidazo[1,2-a]pyridine (410 mg), 1,3-dihydro-2H-pyrrolo[2,3-b]pyridine-2-one (164 mg), trans-N,N′-dimethylcyclohexane-1,2-diamine (174 mg), copper(I) iodide (116 mg), K2CO3 (338 mg) and THF (dry) (5 mL) was heated at 180° C. for 3 h under microwave irradiation. The solid was removed by filtration, and the filtrate was concentrated in vacuo. The residue was purified by column chromatography (silica gel, EtOAc/hexane) to give the title compound (72 mg) as an orange solid (mixture with 1,3-dihydro-2H-pyrrolo[2,3-b]pyridine-2-one, ca. 20% purity).
