3′-Amino-5′-fluoro-2′-hydroxy-biphenyl-3-carboxylic acid hydrochloride 2f (219 mg, 0.772 mmol) was dissolved in 3 mL of hydrochloric acid (1 N) upon cooling by an ice-water bath, followed by dropwise addition of 1 mL of aqueous sodium nitrite (59 mg, 0.85 mmol). After the mixture was stirred for 20 minutes, 2-(2,3-dihydro-benzofuran-5-yl)-5-methyl-2,4-dihydro-pyrazol-3-one 7c (150 mg, 0.69 mmol) was added. The mixture was adjusted to pH 8˜9 by batch addition of aqueous sodium bicarbonate (1.007 g, 11.57 mmol). The generated bubbles were quenched with 2 mL of ethanol. The reaction mixture was warmed up to room temperature and reacted overnight. The reaction was monitored by TLC until the disappearance of the starting materials. The mixture was filtered and the filter cake was dissolved in 15 mL of water. After mixing well, the mixture was adjusted to pH 3˜4 with concentrated hydrochloric acid, filtered and dried. The crude product was purified by HPLC to obtain the title compound 3′-{N′-[1-(2,3-dihydro-benzofuran-5-yl)-3-methyl-5-oxo-1,5-dihydro-pyrazol-4-ylidene]-hydrazino}-5′-fluoro-2′-hydroxy-biphenyl-3-carboxylic acid 14 (65 mg, yield 20.0%) as a red solid.
