To a solution of (5-methyl-3-trifluoromethyl-pyrazol-1-yl)-acetic acid (9.1 g, 36.1 mmol) in DMF (100 mL) is added diisopropylethylamine (45 mL, 216 mmol), followed by O-(benzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium tetrafluoroborate (15.5 g, 39.7 mmol). After stirring 15 min at RT, 2-piperidin-4-yl-thiazole-4-carboxylic acid ethyl ester hydrochloride (10 g, 36.1 mmol) is added to the reaction mixture. After stirring overnight at RT, solvent is evaporated and the resulting yellow oil is dissolved in ethylacetate (300 mL), washed with saturated aqueous sodium bicarbonate solution (300 mL), 1M HCl solution (300 mL), and brine (100 mL). The organic layer is dried over sodium sulfate, filtered, and evaporated under reduced pressure. The crude mixture is purified by column chromatography on silica gel (dichloromethane/methanol 10:1) to give 2-{1-[2-(5-methyl-3-trifluoromethyl-pyrazol-1-yl)-acetyl]-piperidin-4-yl}-thiazole-4-carboxylic acid ethyl ester (13.6 g, 88%). 1H-NMR (400 MHz, CDCl3): δ=1.40 (t, 3H), 1.70-1.85 (m, 2H), 2.16-2.30 (m, 2H), 2.32 (s, 3H), 2.79-2.89 (m, 1H), 3.22-3.43 (m, 1H), 4.03-4.12 (m, 1H), 4.42 (q, 3H), 4.54-4.69 (m, 1H), 4.93-5.08 (2d, 2H (diastereotopic)), 6.35 (s, 1H), 8.10 (br, 1H). MS: m/z=209 (M+1).
