Indanyl-2-acetic acid methyl ester (1.0 g, 5.26 mmol) was added to a stirring solution of chlorosulfonic acid (5 mL) at 0° C. The solution was stirred at 0° C. for 0.5 h, then room temperature for 3 h. The resulting solution was poured slowly over ice and extracted with diethyl ether (3×100 mL). The combined organic layers were dried (Na2SO4) and concentrated to afford a mixture of 5-chlorosulfonyl-indan-2-acetic acid methyl ester and 4-chlorosulfonyl-indan-2-acetic acid methyl ester (1.38 g, 4.78 mmol, 91%). The sulfonyl chloride mixture was taken on to the next step without further purification. The mixture of sulfonyl chlorides (370 mg, 1.28 mmol) were dissolved in dry THF (10 mL). To this solution was added 1-(4-trifluoromethylphenyl)piperazine (315 mg, 1.37 mmol), triethylamine (600 μL, 4.3 mmol) and DMAP (catalytic amount). The reaction was stirred at room temperature for 1 h, concentrated and directly purified by silica gel flash column chromatography to separate the regioisomers (25% ethyl acetate in hexanes) affording {5-[4-(4-trifluoromethyl-phenyl)-piperazine-1-sulfonyl]-indan-2-yl}-acetic acid methyl ester (118 mg, 19%) and {4-[4-(4-trifluoromethyl-phenyl)-piperazine-1-sulfonyl]-indan-2-yl}-acetic acid methyl ester (40 mg, 6%) as clear colorless oils. {5-[4-(4-trifluoromethyl-phenyl)-piperazine-1-sulfonyl]-indan-2-yl}-acetic acid methyl ester: 1H NMR (400 MHz, CDCl3) δ 7.57 (s, 1H), 7.56 (d, 1H), 7.45 (d, 2H), 7.33 (d, 1H), 6.87 (d, 2H), 3.69 (s, 3H), 3.33 (m, 4H), 3.21 (dd, 2H), 3.14 (m, 4H), 2.95 (m, 1H), 2.71 (dd, 2H), 2.52 (d, 2H).
