In the reaction of ethyl N-(1-arylimidazolidine-2-ylidene) carbamic acid ester with 4-chlorobenzylamine new derivatives of 1-(1-arylimidazolidine-2-ylidene)-3-arylurea (I-VI) were obtained. Cyclic derivatives of dihydroimidazo[l ,2-a][1,3,5]trizines were synthesized by condensation of 1-(1-arylimidazolidine-2-ylidene)-3-(4-chlorobenzyl)urea with carbonyldiimidazole (CDI) (VII-XII). The effect of compounds X, XI on the central nervous system of mice in some behavioral tests was investigated.