Potassium Carbonate → ethyl 2-[3-tert-butyl-5-(phenoxycarbonylamino)-1H-pyrazol-1-yl]acetate

In the manner described in Example 161C, using ethyl 2-(5-amino-3-tert-butyl-1H-pyrazol-1-yl)acetate (1.68 g, 7.46 mmol), phenyl chloroformate (1.284 g, 8.2 mmol), and K2CO3 (1.52 g, 11 mmol) in THF (20 mL), which was purified by silica gel chromatography with 0-40% EtOAc/hexane as eluants to afford ethyl 2-[3-tert-butyl-5-(phenoxycarbonylamino)-1H-pyrazol-1-yl]acetate as solid (1.115 g, 43%). 1H NMR (300 MHz, CDCl3) δ 7.37-7.43 (m, 2H), 7.25-7.27 (m, 2H), 7.21 (m, 2H), 6.25 (s, 1H), 4.88 (s, 2H), 4.28 (q, 2H), 1.33 (t, 3H), 1.28 (s, 9H); LC-MS (ESI) m/z 346 (M+H)+.