Magnesium turnings (300 mg, 12.5 mmol) was introduced into a oven-dried flask under N2, covered with anhydrous THF (150 mL), and a solution of dibromobutane (0.72 mL, 6.08 mmol) in anhydrous THF (20 mL) was added dropwise at ambient temperature at such a rate that the temperature of the reaction mixture did not rise above 40° C. The mixture was stirred at ambient temperature for 1 h, and the magnesium turnings disappeared. 1-(2-chloro-phenyl)-5-[5-(3-methanesulfonyl-phenyl)thiophen-2-yl]-1H-pyrazole-3-carboxylic acid methyl ester (2.37 g, 5 mmol) was added as a solid, and the resulting dark-purple solution was stirred at room temperature under N2 for 1 h, At 0° C. aqueous NH4Cl solution was added, and then extracted with EtOAc, The combined extracts were washed with brine, dried over Na2SO4. and evaporated in vacuo. The crude product was purified by flash chromatography (0-60% EtOc/hexanes) to afford the title compound as a white solid (1.4 g, 56%). 1HNMR (CDCl3): δ 8.04 (d, 1H), 7.83-7.81 (m, 1H), 7.74-7.71 (m, 1H), 7.57-7.52 (m, 3H), 7.48-7.44 (m, 2H), 7.20 (d, 1H), 6.74 (d, 1H), 6.63 (s, 1H), 3.07 (s, 3H), 2.42 (brs, 1H), 2.20-1.83 (m, 8H). MS(ES) 499 [M+H]+, 481 (M-OH).
