The present invention relates to the use of compounds of formula (I) wherein R is hydrogen, halogen, lower alkyl, lower alkoxy, hydroxy, phenyl, S-phenyl or O-phenyl, which are optionally substituted by lower alkoxy or halogen, or is benzyloxy, C(O)O-lower alkyl, cycloalkyl, or is lower alkyl or lower alkoxy substituted by halogen; Ar is aryl or heteroaryl, selected from the group consisting of phenyl, naphthyl, pyridinyl, benzofuranyl, dihydrobenzofuranyl or pyrazole; R1/R1' are independently from each other hydrogen, hydroxy, lower alkyl, lower alkoxy or are phenyl or benzyl, which are optionally substituted by halogen; R2 is hydrogen or lower alkyl; n is 1, 2, 3 or 4; and to their pharmaceutically active salts, racemic mixtures, enantiomers, optical isomers and tautomeric forms for the preparation of medicaments for the treatment of depression, anxiety disorders, bipolar disorder, attention deficit hyperactivity disorder, stress-related disorders, psychotic disorders such as schizophrenia, neurological diseases such as Parkinson's disease, neurodegenerative disorders such as Alzheimer's disease, epilepsy, migraine, hypertension, substance abuse and metabolic disorders such as eating disorders, diabetes, diabetic complications, obesity, dyslipidemia, disorders of energy consumption and assimilation, disorders and malfunction of body temperature homeostasis, disorders of sleep and circadian rhythm, and cardiovascular disorders.