The present invention relates to compounds of general formula I wherein R1 is halogen, lower alkyl, lower alkoxy, lower alkyl substituted by halogen, lower alkoxy substituted by halogen or cyano； R2 is hydrogen, CF3 or lower alkyl； R3 is hydrogen, lower alkyl, lower alkenyl, lower alkinyl, heterocycloalkyl, lower alkyl substitueted by cyano, cyano, benzyl substituted by halogen, 2-oxa-6-aza-spiro[3.3]hept-6-yl or is lower alkoxy substituted by halogen； X is -CH2- or -CH2-CH2-； or to a pharmaceutically acceptable acid addition salt, to a racemic mixture or to 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, mild cognitive impairment, chemotherapy-induced cognitive dysfunction, Down syndrome, autism spectrum disorders, hearing loss, tinnitus, spinocerebellar ataxia, amyotrophic lateral sclerosis, multiple sclerosis, Huntington's disease, stroke, radiation therapy, chronic stress, abuse of neuro-active drugs, such as alcohol, opiates, methamphetamine, phencyclidine and cocaine.
