The invention relates to pyrimidin 2-one compounds of general formula (I), in addition to the derivatives and tautomers of (I) and the physiologically acceptable salts of said compounds. In said formula, A represents linear or branched C3-C6 alkene, which can have a double bond or triple bond and/or a group Z, which is not adjacent to the nitrogen atom of the pyrimidinone ring and is selected from O, S, C(O), NR3, C(O)NR3, NR3C(O), OC(O) and C(O)O; B represents a group of the formula (II), in which X stands for CH2 or N and Y stands for CH2 or CH2CH2, or X—Y can also jointly represent C═CH, C═CH—CH2 or CH—CH═CH; R1 and R2 are defined as cited in the description and the claims; and Ar represents an optionally substituted aromatic group. The invention also relates to a pharmaceutical agent, containing at least one compound (I) and the tautomers, derivatives and/or acid addition salts of said compound, optionally together with physiologically acceptable carriers and/or auxiliary agents. The invention also relates to the use of compounds of formula (I), and their tautomers, derivatives and pharmacologically acceptable acid addition salts for producing a pharmaceutical agent for treating diseases which respond to the influence of dopamine D3 receptor ligands.