The compound synthesized in Example 2 (1.4 g) was dissolved in dry acetonitrile (30 ml), and potassium carbonate (1.4 g) was added. The mixture was stirred at room temperature for 30 minutes. Then, benzyl bromide (0.9 g) was added, and the mixture was heated at 50° C. for 2 hours with stirring. The reaction mixture was cooled to room temperature, and poured into water for neutralization. The aqueous layer was extracted with dichloromethane. The crude product was purified by silica gel column chromatography to give the desired N-(2-chloro-5-pyridylmethyl)-N-methyl-N'-(1-benzylthio-2-nitrovinyl)ethylenediamine (0.3 g) having a melting point of 119° to 123° C.
