The present invention relates to a novel compound of formula [I] or a pharmaceutically acceptable salt thereof, and the compound of the present invention comprises schizophrenia, Alzheimer's disease, cognitive dysfunction, dementia, anxiety disorder based on an inhibitory action on glycine uptake. (General anxiety disorder, panic disorder, obsessive-compulsive disorder, social anxiety disorder, post-traumatic stress disorder, specific phobia, acute stress disorder, etc.), depression, drug dependence, convulsions, tremor, pain, Parkinson's disease, attention It is useful for the prevention or treatment of diseases such as deficit / hyperactivity disorder, bipolar disorder, eating disorder or sleep disorder. [Chemical 1]本発明は、新規な式［Ｉ］化合物又はその医薬上許容される塩に関し、本発明の化合物は、グリシン取り込み阻害作用に基づいた統合失調症、アルツハイマー病、認知機能障害、認知症、不安障害（全般性不安障害、パニック障害、強迫性障害、社会不安障害、外傷後ストレス障害、特定の恐怖症、急性ストレス障害等）、うつ病、薬物依存、痙攣、振戦、疼痛、パーキンソン病、注意欠陥・多動性障害、双極性障害、摂食障害、又は睡眠障害等の疾患の予防又は治療に有用である。【化１】
