The present invention relates to compounds of general formula (I) wherein R1 is aryl or heteroaryl, which are optionally substituted by one, two or three substituents, selected from lower alkyl, halogen, lower alkyl substituted by halogen, hydroxy, lower alkyl substituted by hydroxy, lower alkoxy, lower alkoxy substituted by halogen, cyano or nitro； R 2 is halogen, lower alkyl or cyano； R 3 is hydrogen, lower alkyl or lower alkyl substituted by halogen； R 4 is hydrogen or lower alkyl； R5, R 6 are hydrogen, lower alkyl, or may form together with the N-atom to which they are attached a heterocycloalkyl ring； or a pharmaceutically acceptable acid addition salt, a racemic mixture or its corresponding enantiomer and/or optical isomers thereof. The compounds may be used for the treatment of schizophrenia, obsessive-compulsive personality disorder, major depression, bipolar disorders, anxiety disorders, normal aging, epilepsy, retinal degeneration, traumatic brain injury, spinal cord injury, post-traumatic stress disorder, panic disorder, Parkinson's disease, dementia, Alzheimer's disease, cognitive impairment, chemotherapy-induced cognitive dysfunction ("chemobrain"), Down syndrome, autism spectrum disorders, hearing loss, tinnitus, spinocerebellar ataxia, amyotrophic lateral sclerosis, multiple sclerosis, Huntington's disease, stroke, and disturbances due to radiation therapy, chronic stress, or abuse of neuro-active drugs, selected from alcohol, opiates, methamphetamine, phencyclidine and cocaine.La présente invention concerne des composés de formule générale (I), dans laquelle R1 représente aryle ou hétéroaryle, qui sont éventuellement substitués par un, deux ou trois substituants choisis parmi alkyle inférieur, halogène, alkyle inférieur substitué par halogène, hydroxy, alkyle inférieur substitué par hydroxy, alcoxy inférieur, alcoxy inférieur substitué par halogène, cyano ou nitro ； R2 représente halogène, alkyle inférieur ou cyano ； R3 représente hydrogène, alkyle i
