Thionyl Chloride → 6,7-dimethoxy-3,4-dihydronaphthalene-2-carbonyl Chloride

Using 6,7-dimethoxy-1,2-dihydro-3-naphthoic acid (0.8 g), toluene (8 ml) and thionyl chloride (2 ml), a reaction as that described in Example 5 is carried out to give 6,7-dimethoxy-1,2-dihydro-3-naphthoyl chloride. This product is dissolved in N,N-dimethylformamide (3 ml). The solution is added dropwise to a mixture of 1-(3,4,5-trimethoxybenzyl) homopiperazine dihydrochloride (1.2 g), triethylamine (1.36 g) and N,N-dimethylformamide (5 ml) with stirring under ice-cooling. The resulting mixture is stirred at room temperature for two hours. After addition of water, the reaction mixture is extracted with ethyl acetate. The ethyl acetate layer is washed with water, dried and evaporated under reduced pressure. The residue is purified by silica gel column chromatography (ethyl acetate: methylene chloride:ethanol=10:10:1). The resulting oily product is converted to the hydrochloride in ethyl ether to afford 1-(6,7-dimethoxy-1,2-dihydro-3-naphthoyl)-4-(3,4,5-trimethoxybenzyl)homopiperazine hydrochloride (1.4 g) as pale yellow powder.