Sodium borohydride → 2-(5-amino-3-phenyl-4-(phenylethynyl)-1H-pyrazol-1-yl)ethan-1-ol

To a suspension of ethyl 2-[5-acetamido-3-phenyl-4-(2-phenylethynyl)pyrazol-1-yl]acetate (22.4 g, 58 mmol) in ethanol (290 mL) was added sodium borohydride (11 g, 289 mmol) and the reaction stirred at room temperature for 16 h. The reaction mixture was partially concentrated to a final volume of 250 mL. 25% NaOH (250 mL) was added and the reaction mixture was stirred at 80° C. for 4 h. The reaction mixture was cooled down to room temperature and the two phases were separated. The aqueous phase was extracted with ethyl acetate three times and the organic phases combined, dried over MgSO4, filtered and evaporated. The residue was triturated from diethyl ether (20 mL) and the product was filtered and dried in vacuo to provide the title compound as an off-white solid (9.96 g). The mother liquor was concentrated in vacuo and purified by column chromatography (silica gel, gradient 0 to 100% ethyl acetate/isohexane) yielding a further 1.79 g of the title compound.