Abstract In synthetic studies of imidazo [4, 5-c] quinolin-4 (5H)-one derivatives, which exhibit a potent antiasthmatic activity, an unusual rearrangement was observed, where the methyl group migrates from the N-1 to the N-3 position on the imidazole during the reaction of Chapman rearrangement of 1-methyl-4-phenoxy-1H-imidazo [4, 5-c] quinoline 2.