Collect. Czech. Chem. Commun. 1990, 55, 1817-1827

Synthesis of 1-acyl- and 1-(thioacyl)-4-benzylpiperazines as potential antidepressants

Vojtěch Kmoníček, Emil Svátek, Jiří Holubek, Miroslav Ryska, Martin Valchář and Miroslav Protiva

Research Institute for Pharmacy and Biochemistry, 130 60 Prague 3


2-Nitro, 3-nitro- and 4-nitrobenzoyl chloride were reacted with 1-benzylpiperazine in benzene in the presence of triethylamine and gave the amides IV-VI, the first of which is considered a bioisostere of the antidepressant agent piberaline (I). 2-Dimethylamino-, 3-dimethylamino- and 4-dimethylaminobenzoic acid were treated with thionyl chloride in benzene in the presence of triethylamine or pyridine, and the acid chlorides formed were reacted in situ with 1-benzylpiperazine affording the amides VII-IX. The amides I and IV-VI were transformed by treatment with phosphorus pentasulfide in pyridine to the thioamides X-XIII. 4-(Dimethylaminomethyl)benzoic acid was reacted with 1-benzylpiperazine in dimethylformamide in the presence of N,N'-carbonyldiimidazole and afforded the amide XIV. Heating of ethyl 5-methylimidazole-4-carboxylate with 1-benzylpiperazine to 200-210 °C gave the amide XV together with the unexpected 1-benzyl-4-ethylpiperazine (XVI). The oily or crystalline bases of the amino amides or thioamides were mostly transformed to crystalline salts and characterized by spectra. Out of the compounds prepared only X (V⁄FB-17 070) and XIV (V⁄FB-17 114) showed indications of efficacy in tests which are considered indicative of antidepressant activity. Compounds VII, VIII, and X appeared to be mildly antidopaminergic - similarly like piberaline (I), and compounds IV, V, XI, XIV, and XV on the contrary showed signs of dopaminominetic activity.