Short-RInChIKey=SA-FUHFF-UHFFFADPSC-CDDXWUAJGL-UHFFFADPSC-NUHFF-NUHFF-NUHFF-ZZZ

In a vial, ethyl 5-azido-1H-pyrazole-4-carboxylate (50.0 mg, 276 μmol, 1.00 equiv) was dissolved in THF (6.00 mL) and water (6.00 mL) (1:1) and copper;sulfate (8.81 mg, 55.2 μmol, 0.20 equiv), sodium ascorbate (54.7 mg, 276 μmol, 1.00 equiv) and hex-1-yne (29.5 mg, 40.9 μL, 359 μmol, 1.30 equiv) were added. The reaction mixture was stirred at 50 °C for 72 hours. For work up the reaction mixture was diluted in water and extracted three times with methylene chloride. The combined organic phase was washed with water and brine, dried over Na2SO4 and filtered.