The mixture of 3-[4-(benzyloxy)phenyl]-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one (2.50 g), sodium hydride (0.378 g) and iodoethane (1.60 mL) in DMF (25 mL) was stirred at 20° C. under a dry atmosphere (CaCl2 tube) for 1 h. The reaction mixture was diluted with MeOH (10 mL) and concentrated under reduced pressure. The residue was purified by column chromatography (NH silica gel, eluted with 0%-30% EtOAc in hexane) to give 3-[4-(benzyloxy)phenyl]-1-ethyl-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one (2.70 g) as a colorless solid.
