A solution of copper sulfate pentahydrate (2.2 mg; 0.01 mmol; 0.04 eq.) in water (0.2 mL) was added to a mixture of 4-{4-[2-(3-Trimethylsilanylethynyl-phenyl)-pyrimidin-5-yl]-pyrazol-1-yl}-piperidine-1-carboxylic acid tert-butyl ester (intermediate 19, 110 mg; 0.22 mmol; 1.0 eq.), azidomethyl-trimethyl-silane (36 μl; 0.24 mmol; 1.1 eq.) and D-(−)-isoascorbic acid sodium salt (9 mg; 0.04 mmol; 0.2 eq.) in Dioxane-1,4 (3 mL). The vial was sealed and stirred overnight at 8000. The reaction mixture was then diluted with water and extracted with EtOAc (three times). Combined organic phases were washed with brine, dried over magnesium sulfate, filtered and concentrated. Purification by flash chromatography on silica afforded the title compound as a beige solid (60 mg, 49%). 1H NMR (300 MHz, DMSO-d6) δ 9.18 (s, 2H), 8.88 (t, J=1.6 Hz, 1H), 8.57 (s, 1H), 8.54 (s, 1H), 8.34 (dt, J=8.0 Hz, 1.6 Hz, 1H), 8.16 (s, 1H), 7.96 (dt, J=8.0 Hz, 1.6 Hz, 1H), 7.60 (t, J=8.0 Hz, 1H), 4.48-4.38 (m, 1H), 4.11-4.03 (m, 4H), 2.94 (m, 2H), 2.09-2.05 (m, 2H), 1.88-1.74 (m, 2H), 1.43 (s, 9H), 0.13 (s, 9H). MS (ESI+): 559.5.
