2-(2′-Hydroxy-3′-amino-biphenyl-4-yl-4,5-dihydro-1H-imidazol 32d (334 mg, 1.11 mmol) was dissolved in hydrochloric acid (3.7 mL, 1 mol/L) upon cooling by an ice-water bath, followed by dropwise addition of 1.5 mL of aqueous sodium nitrite (85 mg, 1.22 mmol). After the mixture was reacted for 20 minutes, 2-indan-5-yl-5-methyl-2,4-dihydro-pyrazol-3-one 1i (214 mg, 1 mmol) was added. The mixture was adjusted to pH 8 with saturated aqueous sodium bicarbonate, followed by addition of 5 mL of 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 30 mL of water was added to the filter cake. After mixing well, the mixture was adjusted to pH 4 with concentrated hydrochloric acid to form precipitates. The mixture was filtered and the filter cake was purified by silica gel column chromatography to obtain the title compound 4-{[4′-(4,5-dihydro-1H-imidazol-2-yl)-2-hydroxy-biphenyl-3-yl]-hydrazono}-2-indan-5-yl-5-methyl-2,4-dihydro-pyrazol-3-one 32 (145 mg, yield 30.3%) as a red solid.
