A mixture of 3-iodo-7-trifluoromethyl-5-(3-trifluoromethyl-phenyl)-pyrazolo[1,5-a]pyrimidine (6.49 g, 14.2 mmol), trimethylsilylacetylene (3.54 mL, 25.6 mmol) and triethylamine (3.94 mL, 28.4 mmol) in N,N-dimethylformamide (15 mL) was stirred for 10 min at room temperature while being purged with Argon, then PdCl2(PPh3)2 (100 mg, 1 mol %), PPh3 (37 mg, 1 mol %) and CuI (8 mg, 0.3 mol %) were added. Stirring was continued at 90° C. for 4.5 h. The reaction mixture was cooled to room temperature, diluted with ethyl acetate (150 mL), washed with water (2×50 mL) and brine (70 mL), dried (MgSO4) and evaporated to give 7-trifluoromethyl-5-(3-trifluoromethyl-phenyl)-3-trimethylsilanylethynyl-pyrazolo[1,5-a]pyrimidine (6.2 g, 102%) as a light brown solid, which was dissolved in THF (30 mL) and MeOH (70 mL), while stirring at 0° C. potassium carbonate (200 mg, 1.45 mmol) was added and the mixture was stirred at 0° C. for 5 h. The mixture was diluted with ice water (200 mL) and extracted with TBME (3×200 mL). The combined organic layers were washed with brine (300 mL), dried (MgSO4) and evaporated. The crude product was further purified by silica gel column chromatography (heptane/EtOAc 9:1) followed by trituration with heptane to give 3-ethynyl-7-trifluoromethyl-5-(3-trifluoromethyl-phenyl)-pyrazolo[1,5-a]pyrimidine (3.23 g, 63%) as an orange solid. MS (EI) 355.0[(M)+]; mp 154° C.
