3′-Amino-2′-hydroxy-biphenyl-3-carboxylic acid hydrobromide 1f (150 mg, 0.5 mmol) was dissolved in hydrochloric acid (1.7 mL, 1 mol/L) upon cooling by an ice-water bath, followed by dropwise addition of 0.6 mL of aqueous sodium nitrite (38 mg, 0.55 mmol). After the mixture was reacted for 20 minutes, 2-(2,2-dimethyl-indan-5-yl)-5-methyl-2,4-dihydro-pyrazol-3-one 45d (109 mg, 0.45 mmol) was added. The mixture was adjusted to pH 8˜9 with saturated aqueous sodium bicarbonate. Then the generated bubbles were quenched with ethanol. The reaction mixture was reacted overnight at room temperature. The reaction was monitored by TLC until the disappearance of the starting materials. The mixture was filtered and the filter cake was added to 15 mL of water. The mixture was adjusted to pH 3˜4 with concentrated hydrochloric acid and filtered. The filter cake was washed with ethyl acetate (1 mL×3) and then dried to obtain the title compound 3′-{N′-[1-(2,2-dimethyl-indan-5-yl)-3-methyl-5-oxo-1,5-dihydro-pyrazol-4-ylidene]-hydrazino}-2′-hydroxy-biphenyl-3-carboxylic acid 56 (16 mg, yield 7.6%) as a yellow solid.
