A mixture of 2-chloro-1-[2-(propargyloxy)ethyl]-benzimidazole (3.70 g) and N-methylhomopiperazine (9.00 g) is stirred at 120° C. for 5 hours. A 5% aqueous sodium hydroxide (50 ml) is added to the reaction mixture, and the mixture is extracted with ethyl acetate. The extract is washed with water, dried over anhydrous magnesium sulfate and then concentrated. The residue is dissolved in a small amount of chloroform and subjected to column chromatography using silica gel (60 g), and then eluted with chloroform-methanol (10:1 by volume). The eluate is concentrated to give a pale yellow oily substance (1.90 g). The pale yellow oily substance is dissolved in ethanol (3 ml) and the solution is added to a solution of fumaric acid (1.50 g) in hot ethanol (18 ml). After the mixture is allowed to cool, the precipitated crystals are separated by filtration and recrystallized from ethyl acetate-ethanol to give 1-[2-(propargyloxy)ethyl]-2-(4-methyl-1-homopiperazinyl)benzimidazole difumarate (2.14 g) as colorless needles, m.p. 122°-124.5° C.
