A compound which is useful as a dopamine D1 receptor positive allosteric modulator (D1 PAM) is provided. The present inventors have studied a compound which has a dopamine D1 receptor positive allosteric modulating activity and is useful as an active ingredient of a pharmaceutical composition for preventing and/or treating cognitive impairment, negative symptoms of schizophrenia, Parkinson's disease, Alzheimer's disease, Huntington's disease, drug addictions, or the like, and they have thus found that a heterocyclic acetamide compound has a dopamine D1 receptor positive allosteric modulating activity, thereby completing the present invention. The heterocyclic acetamide compound of the present invention has a dopamine D1 receptor positive allosteric modulating activity and can be used as an agent for preventing and/or treating cognitive impairment, negative symptoms of schizophrenia, Parkinson's disease, Alzheimer's disease, Huntington's disease, drug addictions, or the like.本發明的課題為提供一種作為多巴胺D1受體正向異位調節者(D1 PAM)有用之化合物。作為本發明之解決手段，係本發明者們對於具有多巴胺D1受體正向異位調節作用，且作為認知功能障礙、精神分裂症陰性症狀、帕金森氏症、阿茲海默症、亨丁頓舞蹈症，及藥物依賴等之預防及/或治療用醫藥組成物之有效成分有用之化合物進行檢討，確認雜環乙醯胺化合物具有多巴胺D1受體正向異位調節作用，而完成本發明。本發明之雜環乙醯胺化合物係具有多巴胺D1受體正向異位調節作用，可作為認知功能障礙、精神分裂症陰性症狀、帕金森氏症、阿茲海默症、亨丁頓舞蹈症，及藥物依賴等之預防及/或治療劑使用。
