Under a stream of argon gas, 543 mg of 2-nitrophenylacetic acid and 486 mg of carbonyldiimidazole were dissolved in 10 ml of tetrahydrofuran, followed by stirring at room temperature for 10 minutes. Then, 254 mg of 3-amino-5-(4-fluorophenyl)-4-(4-pyridyl)pyrazole and 457 mg of DBU were added thereto, followed by stirring at room temperature overnight. After the reaction mixture was concentrated under reduced pressure, the resulting residue was suspended in chloroform, washed with a saturated aqueous solution of sodium bicarbonate and a saturated aqueous solution of sodium chloride, dried over anhydrous magnesium sulfate, and then concentrated. The resulting residue was purified by column chromatography using 40 g of silica gel [with an elution solvent comprising chloroform-methanol (100:1)]. Thus, 70 mg (14% yield) of the title compound was obtained as a white powder.
