This invention relates to compounds of formula (I), wherein R1 and R3 independently represent fluorine, methoxy, —OCF3, C2-C3-alkenyl or C1-C4-alkyl which is optionally substituted by chlorine, methoxy or one, two or three fluorine atoms; R2 represents hydrogen, fluorine, methoxy, —OCF3, C2-C3-alkenyl or C1-C4-alkyl which is optionally substituted by chlorine, methoxy or one, two or three fluorine atoms; X represents O, S, NH or N(C1-C3-alkyl); and Ar represents an unsubstituted or at least monosubstituted aryl or heteroaryl. Said compounds are inhibitors of poly(ADP-ribose) polymerase (PARP), and may be used for the treatment of a variety of disorders.