A suspension of sodium hydride (60% dispersion in oil; 3.2 g; 80 mmol) in dry tetrahydrofuran (70 mL) under nitrogen at 4° C. is treated with 3,5-dichloro-4-aminopyridine (6.5 g) in dry tetrahydrofuran (80 mL) during 15 minutes and the solution is stirred at room temperature for 1 hour. After cooling to 5° C., it is treated with 3-cyclopentylthio-4-methoxybenzoyl chloride (that is prepared from 9.0 g of 3-cyclopentylthio-4-methoxybenzoic acid as described in Reference Example 47) in dry tetrahydrofuran (80 mL) during 45 minutes, and the temperature is allowed to rise to room temperature. The mixture is treated with a further quantity of tetrahydrofuran (200 mL) and then it is stirred for a further 6 hours. It is then treated with a saturated aqueous solution of ammonium chloride (300 mL), and concentrated in vacuo to low volume. The aqueous residue is extracted with ethyl acetate (2×200 mL). The combined extracts are washed with brine (2×200 mL), dried over magnesium sulfate, and concentrated. The resulting residue is subjected to flash chromatography on silica gel, using a mixture of ethyl acetate and petroleum ether (b.p. 60-80° C.) (1:1 v/v), to give 3-cyclopentylthio-N-(3,5-dichloropyrid-4-yl)-4-methoxybenzamide (2.5 g), in the form of a colorless solid, m.p. 198° C. [Elemental analysis: C,54.5,H,4.6; N,6.95; S,8.2%; calculated: C,54.4; H,4.6; N,7.05; S,8.1%].
