To a suspension of 5-(5-bromo-thiophen-2-yl)-1-(2,4-dichloro-phenyl)-4-methyl-1H-pyrazole-3-carboxylic acid ethyl ester (500 mg, 1.09 mmol), PdCl2(PPh3)2 (23 mg, 0.03 mmol), and CuI (4 mg, 0.01 mmol) in THF (10 mL) was added 4,4-dimethylpent-1-yne (176 mg, 1.30 mmol) and 0.5 M aqueous solution of 2-ethanolamine (3 mL). The resulting mixture was heated at 60° C. for 6 h. After cooled to room temperature, the reaction mixture was poured into water and diethyl ether (H2O/ether=1:1 (v/v), 20 mL). The aqueous layer was extracted with diethyl ether and the combined organic layers were concentrated to give a crude oil, which was purified by flash column chromatography with n-hexane/ethyl acetate (5:1) to afford the desired product (402 mg, 80%) as a light solid.
