Fused heterocyclic compounds

Abstract

The present invention provides a compound which has the effect of PDE 10A inhibition, and which is useful as a medicament for preventing or treating schizophrenia or so on. A compound represented by the formula (1'): wherein, Ring A′ represents an optionally substituted pyridine ring, an optionally substituted pyridazine ring, a pyrimidine ring, or 10 a pyrazine ring, R1′ represents (1) wherein, Rrepresents an optionally substituted phenyl group, or an optionally substituted 5- to 10-membered heterocyclic group, Ring B2 represents a bond, —S—, -0-, —CO—, an optionally substituted methylene group, or —NR— (Rrepresents a hydrogen atom, or an optionally substituted Calkyl group), and Ring Brepresents an optionally further substituted 6- to 10-membered aromatic hydrocarbon ring, or an optionally further substituted 5- to 10-membered aromatic heterocyclic ring, or alternatively, L′ and Rmay be taken together to form an optionally substituted bicyclic or tricyclic fused heterocyclic group, or (2), wherein, Rrepresents an optionally substituted phenyl group, or an optionally substituted 5- to 10-membered heterocyclic group, Ring Brepresents an optionally substituted benzene ring, an optionally substituted pyridine ring, an optionally substituted pyrimidine ring, an optionally substituted pyrazine ring, or an optionally substituted pyridazine ring, Ring D′ represents an optionally further substituted 5- or 6-membered ring, Rrepresents a hydrogen atom, or a substituent, X′ represents ═N— or ═CR—(Rrepresents a hydrogen atom, or a substituent), - - - - - represents that Rand Rmay form, taken together with the carbon atom and the nitrogen atom to which they are each adjacent, an optionally substituted 5- to 7-membered ring when.X′ is ═CR, or a salt thereof.