0.007 ml of pyridine-2-carboxaldehyde and 0.5 ml of nitrobenzene were added to a methanol (1 ml) solution of 37 mg of 4-(2-cyano-phenoxy)-5-(6-methanesulfonyl-pyridin-3-yloxy)-benzene-1,2-diamine obtained in (step 5), and the reaction liquid was stirred overnight at 120° C. The solvent was evaporated away under reduced pressure, and the resulting residue was purified through silica gel column chromatography (developing solvent: chloroform/methanol=20/1) and through partitioning thin-layer chromatography (Kieselgel™ 60F254, Art 5744 (by Merck), chloroform/methanol=15/1) to obtain the entitled compound as a brown solid.
