A mixture of N2-methyl-5-trifluoromethylpyridin-2,3-diamine (0.96 g), 2-allylsulfanylbenzoic acid (1.46 g), WSC (1.06 g), and xylene (10 ml) was stirred with heating at 145° C. for 3 hours. After the mixture was evaporated to remove xylene, acetic acid (10 ml) was added thereto, and stirred with heating at 120° C. for further 1 hour. To the reaction mixture cooled to room temperature, 5 mol/l of aqueous sodium hydroxide solution was added to neutralize, and extracted with ethyl acetate. The organic layer was dried over magnesium sulfate, and concentrated under reduced pressure. The resulting residue was subjected to silica gel column chromatography to give 0.83 g of 2-(2-allylsulfanylphenyl)-3-methyl-6-trifluoromethyl-3H-imidazo[4,5-b]pyridine (hereinafter referred to as Present Compound 10).
