Compounds of formula (I) wherein R1, R2 are independently selected from hydrogen and Cu alkyl； R3 is hydrogen or C1-4 alkyl group which is unsubstituted or substituted by phenyl, pyridyl, or amino optionally substituted by C1-4 alkyl； R4 is hydrogen； R5 is C1-4 alkyl group； R6 is selected from monocyclic aryl, which is a six membered ring unsubstituted or substituted by one or more identical or different groups selected from C1-4 alkyl groups, C1-4 alkoxy, halogenated C1-4 alkyl, phenyl, phenoxy, halogen, nitro； or mono- or bi- or tricyclic heteroaryl group consisting of five or six membered ring(s) having 1 to 3 identical or different hetero atoms selected from nitrogen, oxygen and sulfur, in which at least one of the rings is aromatic, and wherein the rings are optionally substituted by one or more identical or different groups selected from C1-4 alkyl, mono-, di-, tri- halogenated C1-4 alkyl, C1-4 alkoxy, hydroxyl, halogen； their positional isomers, racemates and enantiomers, diastereoisomers, and addition salts with a pharmaceutically acceptable acid, solvates, their complexes, adducts and prodrugs, having a selective dual action on the central GABAergic system, to a process for their preparation and to pharmaceutical compositions containing them.
