(S)-5-(4-Chlorophenyl)-6-(1,1,1-trifluoropropan-2-yloxy)nicotinic acid (0.300 g, 868 μmol) was suspended in t-butanol (3.0 mL). DPPA (358 mg, 282 μl), and triethylamine (87.8 mg, 120 μl, 868 μmol) were added and the reaction mixture was stirred at 100° C. overnight. The mixture was cooled to room temperature, extracted with ethyl acetate and sodium carbonate solution, the organic phase was dried with MgSO4 and concentrated in vacuo. The crude material was purified by flash chromatography (silica gel, 20 g, 5% to 25% ethyl acetate in heptane) to give 0.36 g (99%) of the title compound as white solid; MS (EI) 417.3 (M+H)+.
