A suspension of sodium 2-(5-amino-3-phenyl-4-(phenylethynyl)-1H-pyrazol-1-yl)acetate (2 g, 6.0 mmol) in diethylether (10 mL) and concentrated HCl (50 mL) was cooled at −15° C. before sodium nitrite (0.62 g, 8.0 mmol) in water (5 mL) was added dropwise. The solution was allowed to warm up to room temperature and left stirring for further 18 h. The reaction mixture was carefully quenched with an aqueous solution of Na2CO3 at 10° C., until pH basic, and then extracted EtOAc, backwashed with water then brine, dried (MgSO4) and concentrated in vacuo. The resultant residue was purified using chromatography (silica gel, gradient 2 to 10% diethylether/CH2Cl2) yielding Compound 47 as a yellow foam (580 mg).
