Summary "New Type 10a Phosphodiesterase Inhibitor Compounds" The present invention relates to novel compounds of formula (I) which are type 10a phosphodiesterase inhibitors and their use for the manufacture of a medicament and are thus suitable for treating or control selected medical disorders of neurological disorders and pesiatric disorders, to improve the symptoms associated with such disorders and to reduce the risk of such disorders, where q is o or s, x1 is n or ch, x2 is n or c-r7； x3 is o, s, -x4 = c (r8) - where c (r8) is attached to the carbon atom carrying r2, or -x5 = c (r9) - where x5 is attached to the carbon atom carrying r2； x4 is n or c-r9； x5 is n； het is selected from optionally substituted phenyl, monocyclic hetaryl and bicyclic hetaryl； R1 is selected inter alia from hydrogen, halogen, oh, C1-C4-alkylsulfanyl, C1-C4-alkoxy-C1-C4-alkyl, C1-C4-alkoxy, C1-C4-alkoxy-C1-C4-alkoxy, the y1-cyc1 moiety； R2 is selected inter alia from hydrogen, halogen, oh, C1-C4-alkyl, trimethylsilyl, C1-C4-alkoxy-C1-C4-alkyl, C1-C4-alkoxy, C1-C4-alkoxy-C1-C4- alkoxy, C 2-4 alkenyloxy, etc .； a represents one of the following groups a1, a2, a3, a4 or a5: where * indicates the binding points in het and the nitrogen atom, respectively； and where r3 to r9, r3e, r3f, a ', y1 and cys1 are as defined in the claims.resumo “novos compostos inibidores de fosfodiesterase tipo 10a” a presente invenção refere-se a novos compostos da fórmula (i) que são inibidores da fosfodiesterase tipo 10a e ao seu uso para a fabricação de um medicamento e que desse modo são adequados para tratar ou controlar transtornos médicos selecionados de transtornos neurológicos e transtornos pesiquiátricos, para melhorar os sintomas associados com tais transtornos e para reduzir o risco de tais transtornos, em que q é o ou s, x1 é n ou ch, x2 é n ou c-r7； x3 é o, s, -x4=c(r8)-, onde c(r8) é ligado ao átomo de carbono que carrega r2, ou -x5=c(r9)-, onde x5 é ligado ao átomo de carbono que carrega r2； x4 é
