PROBLEM TO BE SOLVED: To provide a novel compound useful for treatment or prevention of diseases such as sleep disorder, depression, anxiety disorder, panic disorder, schizophrenia, drug dependence, Alzheimer disease, Parkinson disease, Huntington chorea, eating disorder, headache, migraine, pain, digestive system disease, epilepsy, inflammation, immunity-associated diseases, endocrine related diseases, hypertension based on an orexin (OX) receptor antagonism, or a pharmaceutically acceptable salt thereof.SOLUTION: There is provided a compound represented by the formula (I) and a pharmaceutically acceptable salt thereof.SELECTED DRAWING: None【課題】 オレキシン（ＯＸ）受容体拮抗作用に基づいた、睡眠障害、うつ病、不安障害、パニック障害、統合失調症、薬物依存症、アルツハイマー病、パーキンソン病、ハンチントン舞踏病、摂食障害、頭痛、片頭痛、疼痛、消化器疾患、てんかん、炎症、免疫関連疾患、内分泌関連疾患、高血圧等の疾患の治療又は予防に有用な新規化合物又はその医薬上許容される塩を提供することである。【解決手段】 式（Ｉ）で示される化合物又はその医薬上許容される塩。【化１】【選択図】なし
