A compound represented by the formula (I): wherein each symbol is as described in the SPECIFICATION, or a salt thereof has a PDE2A inhibitory action, and is useful as a prophylactic or therapeutic drug for schizophrenia, Alzheimer’s disease and the like.一種式(I)所示之化合物或其鹽:其中,各符號係如說明書中所描述,其具有PDE2A抑制作用,而且有用於作為精神分裂症、阿茲海默症及類似者之預防性或治療性藥物。由於第1圖為實驗例結果圖,並非本案的代表圖。故本案無指定代表圖。