The present invention relates to compounds of formula I
wherein
R
1
,
R
2
, X
1
, and X
2
are as defined in the specification and to pharmaceutically acceptable acid addition salts thereof. Such compounds are inhibitors of the glycine transporter 1 (GlyT-1) and can be used in the treatment of schizophrenia, cognitive impairment, and Alzheimer's disease.
[4-(HETEROARYL)PIPERAZIN-1-YL]-(2,5-SUBSTITUTED -PHENYL)METHANONE DERIVATIVES AS GLYCINE TRANSPORTER 1 (GLYT-1) INHIBITORS FOR THE TREATMENT OF NEUROLOGICAL AND NEUROPSYCHIATRIC DISORDERS