4-Methoxybenzoic acid (0.64 g, 4.2 mmol) was dissolved in N,N-dimethylformamide (25 ml) and 1-hydroxybenzotriazole (0.71 g, 5 mmol) was added followed by N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride (0.96 g, 5 mmol). The resulting mixture was stirred at room temperature for 30 minutes. 4-(4-Trifluoromethoxyphenyl)-4,5,6,7-tetrahydro-thieno[3,2-c]pyridine (1.5 g, 5 mmol) followed by N,N-diisopropylethylamine (1.4 ml, 8.4 mmol) were added and the resulting mixture was stirred at room temperature for 16 hours. Water (10 ml) was added and the mixture was extracted with diethyl ether (3×20 ml). The combined organic extracts were washed with saturated aqueous ammonium chloride (20 ml), dried over MgSO4 and concentrated in vacuo. The residue was purified by column chromatography over silica gel eluting with a mixture of ethyl acetate and heptane (1:2). The pure fractions were pooled and concentrated in vacuo. The residue was crystallised from a mixture of methyl tert-butyl ether and heptane to afford 2.13 g (98%) of the title compound.
