| abstract |
The present invention provides a compound useful as a medicament for preventing or treating schizophrenia and the like, which has a PDE inhibitory action. A compound of the formula (I 0 ) or a salt thereof: (Wherein, R 1 represents a substituent, R 2 represents a hydrogen atom or a substituent, R 3 represents a hydrogen atom or a substituent, Ring A represents an aromatic ring which may be substituted, And ring B represents a 5-membered heteroaromatic ring which may be substituted). |