[5-Methyl-2-(phenylthio)phenyl]acetic acid (XV) was synthesized on the one hand from the acid VIII using the known homologization technique via the alcohol X and nitrile XII, on the other from 5-methyl-2-(phenylthio)acetophenone (XIII) by means of the Willgerodt reaction. Via the intermediates XIX and XX, the synthesis led to 10-chloro-2-methyl-10,11-dihydrodibenzo[b,f]thiepin (XXI), giving by treatment with 1-methylpiperazine and 1-(2-hydroxyethyl)piperazine the title compounds III and IV. These compounds have low cataleptic and high central depressant activity; on the other hand, they do not influence the levels of dopamine metabolites in the rat brain which is considered an indication of their lacking the neuroleptic character.