The present invention relates to compounds of the general formula I wherein Het is oxazole-5-yl, pyridin-4-yl, or pyrazol-4-yl R1/ R2 are, independently from each other, hydrogen, lower alkyl, lower alkoxy, or halogen W is -CH2- or -CH2CH2- X is CR3R4 or NR5 R3 is hydrogen or lower alkyl R4 is -(CH2)n-phenyl, optionally substituted by halogen, lower alkoxy, lower alkyl substituted by halogen, lower alkoxy substituted by halogen or lower alkyl R5 is CHR-phenyl or CH2CHR-phenyl, optionally substituted by halogen, lower alkoxy, lower alkyl substituted by halogen, lower alkoxy substituted by halogen or lower alkyl, or is CHR-pyridin-2, 3 or 4 -yl R is hydrogen or lower alkyl n is 0 or 1 or to a pharmaceutically acceptable acid addition salt, to a racemic mixture or to its corresponding enantiomer and/or optical isomer thereof. The compounds may be used for the treatment of schizophrenia, obsessive-compulsive personality disorder, depression, bipolar disorders, anxiety disorders, normal aging, epilepsy, retinal degeneration, traumatic brain injury, spinal cord injury, post-traumatic stress disorder, panic disorder, Parkinsons disease, dementia, Alzheimers disease, cognitive impairment, chemotherapy-induced cognitive dysfunction, Down syndrome, autism spectrum disorders, hearing loss, tinnitus, spinocerebellar ataxia, amyotrophic lateral sclerosis, multiple sclerosis, Huntingtons disease, stroke, radiation therapy, chronic stress, 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 Het représente un groupe oxazole-5-yle, pyridin-4-yle ou pyrazol-4-yle R1/ R2 représentent chacun indépendamment lun de lautre, un atome dhydrogène, un groupe alkyle inférieur, alcoxy inférieur ou un atome dhalogène W représente -CH2- ou -CH2CH2- X représente CR3R4 ou NR5 R3 représente un atome dhydrogène ou un groupe alkyle inférieur R4 représente -(CH2)n-phé
